Seminars Archive

TBA

Brown dwarfs are high-quality testing grounds for atmospheric models and optimizing requirements for exoplanet-focused instrumentation. Brown dwarfs have similar atmospheric physics and chemistry to gas giant exoplanets, but are much easier to observe because they do not suffer from host star obscuration. I will discuss the importance of mid-infrared wavelengths and needed development to understanding planetary atmospheres in the JWST and the ELT-era.  First, I will share the results of a JWST program studying WISE 0855 (280K), the coldest known brown dwarf and the best analog for studying processes that also occur on gas giant planets within our Solar System. We present high SNR (80 – 100), medium resolution (R ∼1000), time-series JWST/NIRSpec spectra of WISE 0855. Our observations span 11 hours with 15-minute pointings covering 2.87–5.27 microns. The dominant time-variable feature is carbon monoxide (CO) gas absorption, producing modulations in its band strength with peak-to-peak amplitudes of 8%. We discuss the changes in CO in the context of other expected disequilibrium species such as phosphine and carbon dioxide. Using atmospheric and structural models, we find that the changes in CO and temperature must originate from distinct surface features and water clouds on WISE 0855. Second, I will share development for a third generation instrument for the Large Binocular Telescope.

Groundwater provides 40% of the water used in California for public supply and agriculture, and this figure is higher in drought years. Understanding surface and groundwater connections is central to storing groundwater for municipal use and supporting ecosystems but very difficult to measure. In this talk, I will present my isotope hydrogeology research to track where water comes from and how long it has been in the subsurface, using stable isotopes as source “fingerprints” and radioactive isotopes as “timers”.

In Livermore Valley, imported water from the California aqueduct system is isotopically distinct from local basins. I will show how this distinction enables me to track the infiltration of applied surface water into the groundwater system to evaluate the efficacy of sustainability planning and to understand how these efforts also support groundwater dependent ecosystems. I then use novel short-term isotope tracers to quantify the contributions of different water years to groundwater wells, calculating recharge rates for use in regional flow models. This analysis shows where and when recharge has been most effective.

Lastly, I will discuss how this water security research can be expanded to other priority sites such as the Central Valley and beyond, using machine learning and working directly with resource managers.

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Characterizing molecular mechanisms of marine carbon transformations is vital for predicting future changes to the marine carbon cycle. One-carbon molecules (e.g., methane, methanol, formate, carbon monoxide) are increasingly recognized as key energy and carbon sources for marine microbes. In this talk, I will highlight recent findings about the importance of nontraditional bio-essential trace elements, particularly tungsten and light rare earth elements, for metalloenzymes that catalyze microbial one-carbon metabolisms in the ocean. Alphaproteobacteria involved in one-carbon transformations in surface seawater may provide insights about the bacterial ancestor of mitochondria. They may also possess novel proteins for sensing, scavenging, and storing critical elements at picomolar concentrations in seawater that may be relevant for biotechnology.

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The dynamics of glaciers and ice sheets influence rates of sea-level rise, freshwater supplies, and landscape evolution. Decades of research has highlighted key processes and connections between terrestrial ice, the climate, and the solid earth, but limited observations have allowed fundamental questions in glaciers dynamics to remain open. In this talk, we will explore some related questions: What is the viscosity of glacier ice and how does it depend on stress? Why does ice fracture? Building on these fundamental questions, we will highlight new efforts to support polar science and accelerate improvements in our ability to observe and model ice sheets. 

In this talk I am going to explore the interplay between tectonic and surface processes in shaping Cordilleran-type orogenic systems, having the Central Andes as the main study case. The Escoipe Canyon in NW Argentina cross cuts the fold-and-thrust belt of the Eastern Cordillera, which makes the transition from the Puna Plateau to the modern foreland region. A new dataset of multiple low-temperature thermochronometers records the history of orogenic building from rifting to foreland basin, and ultimately the thrust belt forming the present-day orographic barrier of the Central Andes. The apatite (U-Th)/He data, however, dates the last 10 myr of history after the main episode of shortening, and shows a westward trend of younger cooling ages, opposite to the regional cooling trend in the thrust belt. I will explore a hypothesis regarding climate and surface processes controlling rock exhumation in the canyon, and the impacts on orogenic evolution. Additionally to this data-driven study case, I will show some effects of orography in Cordilleran-type systems in the lithospheric scale using geodynamic models, and demonstrate that surface processes might affect strain distribution and lithospheric removal processes.

Climate change is stressing the American West’s century-old system of water storage and conveyance, through longer and more intense droughts and periods of exceptional rainfall and flooding. Nowhere are these challenges more acute than in California’s Central Valley, which produces 25% of the USA’s agricultural output on climatologically marginal farmland. Intense management of mountain discharge into the Central Valley, along with oversubscribed rights to surface water, have resulted in unchecked exploitation of the Valley’s groundwater resources and impeded initiatives to use occasional surface water surpluses for aquifer recharge.

New regulation has sparked interest in better information on groundwater availability. Here at Scripps, our lab uses remotely sensed observations of Earth’s gravity and surface motion to infer the dynamics of the hydrological system that feeds the Central Valley aquifer. These techniques track the evolution of mountain water storage at various timescales, and they reveal how this stored water enters and flows through the Central Valley aquifer. Effective management of groundwater resources in the Central Valley will require adoption of data-informed policies, and our hope is that our insights into Central Valley hydrology will prove useful to this end.

50+ years after the Apollo missions, NASA will be sending astronauts back to the Moon. This time, the astronauts will land near the South Pole of the Moon. The Lunar Environment Monitoring Station (LEMS-A3) is one of the selected Artemis III Deployed Instruments. LEMS-A3 is built to operate independently of the Artemis III crew spacecraft, survive the lunar night and operate for at least two years. The LEMS-A3 payload is a set of astronaut-deployed seismometers, SeisLEMS, consisting of a broadband (BB) and short period (SP) instrument built by the University of Arizona and Silicon Audio Inc. Artemis astronauts will deploy and position LEMS-A3, and bury the BB and SP instruments into an astronaut dug-trench and borehole, respectively.
The BB and SP will continuously record ground motions at 100 samples per second (sps) and relay 15 sps data back to Earth once a month. The LEMS team will use the ground motions to detect and locate lunar seismic events including impact-driven, shallow, and deep moonquakes and iteratively backfill the events with 100 sps data. The proposed Artemis III landing sites all enable seismic surveys of the southern pole and farside of the Moon; geographic regions that have previously be unexplored with seismometers. Through seismic data interpretation we aim to catalog seismicity of the Moon, investigate the crustal and mantle structure of the south pole, determine the structure of the deep interior, and ascertain seismic hazards.
Although LEMS-A3 is designed as a stand-alone seismic station, it is possible that it may operate at the same time as other seismometers, e.g. the Farside Seismic Suite (FSS) and other future lunar missions equipped with seismometers. If FSS and LEMS-A3 are operational at the same time, more science may be accomplished through collaboration of the science teams and shared datasets.

The modern world teems with complex life—the animals, plants, fungi, seaweeds, and a dazzling array of single-celled organisms known as the protists. All of these are part of the eukaryotic clade, descended from a common ancestor that lived more than 1 billion years ago. In this talk, I will provide an overview of early eukaryote evolution and the environmental context in which they evolved.  I will present new research that sheds light on the habitats in which eukaryotes lived and how they might have survived the extreme “snowball Earth” glaciations that entombed the planet in ice 720–635 million years ago (Ma). Finally, I will highlight the outstanding questions that remain, including what drove their rise to dominance during the late Neoproterozoic Era (~600 Ma).

Statically stable density stratification is ubiquitous in geophysical flows. It tends to suppress vertical motions, leading to thin, sheared layers and highly anisotropic structures. This talk discusses recent progress in understanding stratified turbulence, including mixing efficiency and the role of intermittent events, and highlights open questions relevant to oceans and atmospheres.

Juno and Cassini have revealed that Jupiter and Saturn likely contain broad regions where heavy elements are mixed gradually, rather than being sharply separated. A major open question is how these composition gradients can survive for billions of years, even though the planets’ interiors are vigorously convecting.

In this talk, I’ll present numerical simulations that explore how convection mixes compositional gradients in a simplified model of a planet’s interior. I’ll show that rotation can play an important role in shaping the flow and can strongly influence how efficiently composition is mixed. Also, I will show that under certain conditions, the combined effects of temperature and composition cause the fluid to organize itself into stacked convective layers, remarkably similar to the layers that form in a latte. I’ll conclude by discussing the challenges for our understanding of convective mixing and what this means for giant planet interiors.

Planets exhibit extraordinary diversity in physical properties and orbital architectures, spanning more than four orders of magnitude in mass, separation, and age. Interpreting this landscape is challenging as observational biases and orbital migration obscure the pathways of planet formation and evolution across both space and time. While the full picture remains incomplete, a story is emerging for gas giants from radial velocity surveys probing planetary systems from the inside out and high-contrast imaging from the outside in. These complementary approaches are converging at intermediate scales, enabling a more continuous view of giant planet populations. I will present results from recent ground- and space-based efforts to constrain how giant planets assemble and evolve, focusing on accretion disks, population demographics, orbital eccentricities, and stellar spin–orbit misalignments. Together, these are informing the processes of gas accretion, angular momentum exchange, and dynamical evolution that shape planetary systems. I will also highlight how upcoming astrometric discoveries from Gaia—which is expected to reveal thousands of giant planets at intermediate separations later this year—will help bridge the gap between inner and outer planet populations and clarify how giant planets form and interact over time.

In its travel through the Milky Way, the Sun traverses a variety of Galactic
environments, including dense interstellar clouds. Astronomical effects on
Earth’s past climate have been limited to 10,000-year scales variations in
Earth’s orbital parameters while our recent studies suggest that
longer-term climate shifts that occur every few million year may be linked
to compression of the heliosphere (the “cocoon” formed by the solar wind)
when the Sun crosses dense clouds as it travels through the Milky Way.
During such periods Earth was exposed to increased radiation and large
amounts of hydrogen, potentially altering its climate. These events are
consistent with independent 60Fe records indicating nearby astrophysical
encounters at ~2–3 and ~6–7 million years ago (Ma), as well as 10Be
anomalies near ~10 Ma that may reflect prolonged exposure to enhanced
radiation during a cold cloud crossing.  A convergence of recent advances
across astronomy, space physics, and paleoclimate creates an unprecedented
opportunity to rigorously test this hypothesis. We now have high-precision
astrometry from the Gaia mission that allows one to reconstruct the Sun’s
trajectory through the Galaxy and to identify, with remarkable accuracy,
the interstellar structures it has encountered over the past ~10 Ma. Major
theoretical and modeling advances now enable quantitative predictions of
how the heliosphere evolved during these encounters. In this talk I will
discuss our recent work that show that during such periods, Earth was
exposed to increased radiation and large amounts of hydrogen. I will
discuss our preliminary results that show that the increase in hydrogen
augmented mesospheric water vapor, leading to increased formation of both
polar mesospheric clouds and polar stratospheric clouds. The amount of
radiation that Earth experiences from such events depends on the duration
of the crossing and the amount of compression of the heliosphere, with
implications for Earth’s climate. I will discuss our results as well that
indicate that high temporal 10Be signal in ocean records and ice cores can
distinguish between alternative scenarios such as supernova explosions and
cold cloud crossings.

The 2028 Summer Olympics will be held in Los Angeles from July 14–30, making Los Angeles only the third city(after London and Paris)to host the Summer Games three times. Los Angeles is an attractive Olympic venue not only because of its mild climate and global tourist appeal, but also because of its remarkable physical setting: a major coastal metropolis situated adjacent to actively deforming mountain ranges rising to elevations above 10,000 feet. This unique geological context provides an exceptional opportunity to connect a globally watched sporting event with public understanding of how Earth systems operate.
The geology of the Los Angeles region is far more dynamic and diverse than that of other Summer Olympic host cities. The convergence of intense public interest in the Olympics with an unusually compelling natural setting creates a rare opportunity for large-scale informal STEM education focused on Earth science and natural history. Leveraging this moment could engage audiences ranging from K–12 students to lifelong learners, both locally and worldwide. We refer to this proposed effort as the LA2028 GeOlympics.

This initiative aims to capitalize on global attention surrounding the 2028 Games by providing accessible, place-based explanations of the geological history of the Los Angeles region, particularly around Olympic venues, and by illustrating how tectonics, climate, and surface processes have shaped this iconic landscape. Achieving this goal will require coordinated collaboration among the region’s extensive educational and cultural infrastructure, including 14 college and university geology departments, 19 community colleges, approximately 2,000 K–12 schools, 136 museums, hundreds of environmental organizations, and a broad range of media outlets. This presentation outlines the vision for LA2028 GeOlympics, discusses organizational and funding needs, and explores pathways for collaboration with the LA28 Organizing Committee to transform the Olympics into a powerful platform for Earth science education.

The discovery of thousands of exoplanets revealed a huge variety in the sizes, masses, and orbital properties of planets outside of our solar system. I will discuss how the physics of gas accretion, dust-gas interaction, and star-disk-planet interaction can shape the observed diversity, providing explanations for some of the puzzling demographic patterns that have emerged in exoplanet science while placing our solar system in the larger Galactic context.

Planetary atmospheres are not static in time, and the many changes they experience can contribute to making a planet’s surface a more (or less) hospitable place. Interactions between a planet and its host star are especially important. They not only control the temperature of an atmosphere but can also drive atmospheric escape and atmospheric chemistry. In this presentation I describe ongoing efforts to understand what characteristics of a planet and its star, when combined together, allow the planet to retain an atmosphere that might be habitable at the planet’s surface. I’ll describe observations from planets in our solar system that inform this work, relevant modeling and observational efforts, and a team science effort dedicated to answering this guiding question.

Recent advances in Earth observation and computational techniques allow for the rigorous examination of climate and coastal sediment dynamics at scale. Leveraging these novel methods, we investigate how severe storms and oscillations in Earth’s climate affect Great Bahama Bank (GBB), the world’s largest modern isolated carbonate platform. High-fidelity hydrodynamic simulations suggest that a single hurricane has a negligible effect on the broad-scale distribution of sediments on the platform top, which is predominately sculpted by fair-weather conditions. Nevertheless, multi-decadal satellite monitoring intimates that catastrophic hurricanes, when occurring in quick succession, may be responsible for the remobilization of mud months to years after their passage. On longer time scales still, interannual and decadal variations in suspended sediment are linked to windy El-Niño events, tidal-forcing Lunar Nodal Cycles, and the weakening of the Atlantic Meridional Overturning Circulation. Spatial variations abound too. Surprisingly, sediment lofting along the leeward margin is linked to wind, while tide dictates resuspension on the windward margin. Finally, we present evidence others have found in the Holocene sedimentary record of the same climate signals we observe in the modern – linking platform top sediment dynamics to slope sedimentation. In doing so, we shed light on how modern analogues can be used to constrain past climate signals and predict sedimentological responses in the future.

The Juno spacecraft has been orbiting Jupiter since July 2016 and is completing its first extended mission.  My personal list of the five most important things we’ve learned from the Juno mission during its prime and extended missions goes something like this: 1. Jupiter has a fuzzy core. 2. Moist convection really is a dominant feature of Jovian atmospheric dynamics 3. Water seems to be supersolar in abundance, at least down hundreds of bars pressure.  4. Europa has a platypus-shaped crustal melt region. 5. There is an active lava flow at Zal Montes on Io.

The heat flow of a planetary body plays a major role in defining its evolution and current composition, driving processes from internal differentiation during its formation through geological activity at the current time. In this talk, I will describe how the ALMA (sub-)millimeter observatory and the James Webb Space Telescope are shedding light on the heat flow histories of satellites and small bodies. Thermal emission observations of asteroids provide information on the abundance and form of metals (ALMA) and minerals (JWST) on their surfaces. I will present ongoing asteroid programs aimed at providing a more complete compositional picture of asteroid surfaces, with implications for the early heating and differentiation of planetesimals. ALMA can also measure the isotopes of the volatile-forming elements, a key tool for studying the formation and evolution of objects in the Solar System. I will discuss sulfur and chlorine isotopes in the volcanic gasses of Jupiter’s moon Io in particular, and how they place constraints on the tidal heating and volcanism that Io experienced over the age of the Solar System.

Hot Jupiters — giant planets on short-period (< 10 days) orbits around their host stars — represent the most extreme outcome of planet formation. Even though they were the first type of exoplanet around Sun-like stars to be discovered, their origins remain unclear. One challenge is our limited understanding of hot Jupiter statistics, as most of them were discovered by a heterogeneous collection of ground-based surveys with a variety of biases. NASA's Transiting Exoplanet Survey Satellite, a uniform all-sky transit search, presents the opportunity to revolutionize hot Jupiter demographics by unifying these previous planet searches. Over the past few years, I led the TESS Grand Unified Hot Jupiter Survey to confirm and characterize hundreds of planet candidates from TESS with facilities like Keck and Magellan. I will present the 4-sigma detection of a pile-up in the period distribution, the dependence of hot Jupiter occurrence on host star properties, and new evidence that they are found around a kinematically young galactic population. I will also discuss how our survey is enabling new lines of inquiry including the discovery of giant planets in the galactic thick disk, as well as detailed characterization of benchmark systems to test key physical processes like tidal inflation and orbital decay.

The field of exoplanets is evolving with astronomical speed, with over 6000 exoplanets discovered to date, including many planets that have no counterparts in the Solar System. More recently, the James Webb Space Telescope has revolutionized our understanding of exoplanet atmospheres by delivering unprecedented spectroscopic constraints on their atmospheric compositions.
In this talk, I will talk about my journey as a planetary scientist who started in the lab working with organic materials on Titan, and how I transitioned to working on some fun theoretical problems for exoplanet atmospheres. Specifically, I will discuss how we can use atmospheric composition to understand the nature and potential habitability of temperate sub-Neptunes, planets with sizes ranging between Earth and Neptune, which also represent the most common type of exoplanets discovered to date. I will also highlight my recent work addressing the emerging population of “missing methane” exoplanets.

The early evolution of the Earth-Moon system prescribes the tidal environment of the Hadean Earth and holds the key to the formation mechanism of the Moon. Estimating its early state by backtracking from the present, however, suffers from considerable uncertainties associated with ocean tides. Tidal evolution during the solidification of Earth’s magma ocean, on the other hand, has the potential to provide robust constraints on the Earth-Moon system before the appearance of a water ocean. To this end, it is of vital importance to understand how energy dissipates in a solidifying magma ocean and how tidal dissipation interacts with atmospheric evolution. These issues have turned out to be much more complicated than previously thought, and as it stands, many of the existing variations of the Moon-forming giant impact hypothesis appear to be unable to explain the present-day angular momentum of the Earth-Moon system, calling for further innovative ideas on the formation of the Moon.

Earthquakes occur naturally driven by tectonic processes, but they can also be induced by human activities. In particular, earthquakes induced by extraction or injection of fluids in the subsurface — during gas production, CO2 storage of geothermal operations for example — provide an opportunity to investigate earthquake physics and to test earthquake forecasting models. Our research shows that, in such examples, spatial and temporal variations in seismicity rate can be predicted reliably from stress changes inferred from reservoir operations and surface deformation measurements. These advances can improve methods for time-dependent seismic hazard assessment. However, forecasting individual events remains a major challenge.

The dynamics of energetic electron fluxes in Earth’s radiation belts are conventionally described by two dominant mechanisms: (1) wave–particle resonant interactions, resulting in acceleration and pitch-angle scattering, and (2) radial diffusion driven by ultra-low-frequency (ULF) waves. However, observations often reveal behavior that cannot be fully explained by these processes, indicating the need for additional radial transport mechanisms beyond classical diffusion. Indeed, radial transport can arise even in the absence of waves, solely due to the topology of magnetic field lines. This mechanism is known as Drift-Orbit Bifurcation (DOB), which occurs on the dayside, where solar wind compression splits the equatorial magnetic field minimum into two off-equatorial minima, violating the second adiabatic invariant and enabling radial transport. While previous studies have primarily considered symmetric magnetic field configurations, we conduct a detailed investigation of realistic DOB under north–south and east–west asymmetries introduced by the IMF direction and dipole tilt angle. We find that such asymmetric configurations produce large jumps—of the order of the adiabatic invariant itself—in the second adiabatic invariant. Moreover, we show that these jumps closely correspond to the so-called geometric jumps well known in Hamiltonian systems theory. Using a Hamiltonian framework and large-scale guiding-center simulations, we show that these jumps can drive substantial radial transport within a single drift period. We discuss the implications of this new radial transport mechanism in the context of energetic electron transport near the magnetopause. These results shed new light on observations of isolated enhancements of >30 keV electrons, as observed by equatorial spacecraft (THEMIS) as well as low-orbit spacecraft such as CubeSats (ELFIN/CIRBE) and POES.

Turbulence is an important mechanism for energy conversion in weakly collisional plasmas. In fluid turbulence, energy injected into the system at large spatial scales is transferred to smaller scales until it is dissipated as heat through collisions. In the interim between energy injection and dissipation, kinetic effects can also mediate the dissipation of energy below characteristic fluid (ion) scales. There is a longstanding question concerning plasmas with low collisional rates: How does this energy conversion process end without collisions? In addition, this classical understanding of turbulence is, in nature, based on a velocity-averaged theory of Vlasov-Boltzmann systems. The energy in consideration is that of the plasma bulk motion; the transfer process is one through space. Since a Vlasov-Boltzmann description concerns both space and velocity, we can also ask the question: Is there a conjugate spatial-averaged theory of turbulence, one that describes a turbulent energy transfer instead through velocity?
In this talk, we explore these two questions regarding turbulence in space and in velocity with MMS observations in two regions in the Earth’s magnetosphere. In the magnetotail, explosive large-scale magnetic reconnection generates strong turbulence with low density and background field. The electromagnetic field spectra are well resolved below electron scales, suitable for turbulence studies of kinetic effects. We show evidence of a sub-electron kinetic range where the energy transfer process appears to complete. In the magnetosphere, the distribution function is well resolved with MMS instruments, suitable for turbulence studies of fine structures in velocity space near fluid scales. We show the first ever statistical observation of velocity-space cascade using data from the MMS unbiased magnetosheath campaign

It has been established since the Helios epoch and confirmed by Ulysses and SOHO that the sources of fast solar wind streams at solar minimum are the polar coronal holes, while slower solar wind streams have contributions from different sources. The larger than expected filling factor of slow solar wind has been attributed to flows coming from coronal hole boundaries, i.e., regions with large expansion factors, or from regions where the mapping of the magnetic field from the photosphere into the heliosphere is complex, as identified for example by the squashing factor, and known as the S-Web.
The observations by Parker Solar Probe that much of the solar wind, independently of speed, is dominated by Alfvénic fluctuations, and the frequent observation of slow Alfvénic solar wind, previously observed relatively rarely in Helios and Wind data, provide evidence for a picture of solar wind origins that incorporates both the expansion factor and S-web paradigms: both coronal holes with large expansion and S-Web regions act as slow solar wind sources, with the difference that highly expanding coronal holes provide Alfv.nic slow streams, while the S-web wind is unlikely to exhibit strong Alfvénic correlations.
As far as the fast solar wind is concerned, we focus on a new aspect associated with the interaction of spherically polarized Alfvén waves and the background wind. It arises from the continuous presence of spherically polarized Alfvénic fluctuations, in the form of switchbacks and patches of switchbacks, that lead the solar wind to be formed of multitudes of one-sided jets. We call the average effect of such jets the Gosling boost, as Jack Gosling was the first to recognize such one-sided jets over the baseline unperturbed solar wind expansion. Here we show how the Gosling boost provides direct empirical evidence for the acceleration of the wind by Alfvénic fluctuations and discuss the more general question
of the origin and acceleration of Alfvénic solar wind streams.

Decades of spacecraft and telescope observations of Jupiter’s upper atmosphere reveal that plasma emissions, densities, temperatures and vertical structure do not appear to be controlled by sunlight alone. In this talk, I will present a recently developed unified picture in which neutral winds, acting along Jupiter’s spatially complex magnetic field via field aligned ion–neutral coupling, drive vertical transport that organizes the non auroral ionosphere and creates the steady spatial patterns seen in ~60 years of observations.

This unified view has been informed by 5 complementary studies: a reanalysis of ~6 decades of spacecraft radio occultations (Pioneer, Voyager, Galileo, Juno) which reveal significant variability in plasma vertical structure; over 175,000 spectra from ground-based telescopes (KECK/NIRSPEC), collected across four years, that produce high resolution global maps of ion densities and temperatures; a coordinated 2023 campaign (Juno, JWST, Keck) that delivered simultaneous continuous electron and ion vertical profiles; a new general circulation model of Jupiter’s thermosphere (JTIM) and ionosphere, which produces the first global wind maps consistent with observed temperatures; and a novel Jovian ionosphere model (JAMMIES) which includes an approximation of Jupiter’s magnetic field geometry and can reproduce various observed phenomena through its comprehensive treatment of ionospheric transport at Jupiter.

Finally, I will briefly discuss the outstanding mysteries still persist, concerning how such an ionosphere feeds back on magnetospheric currents, and the unknown drivers that control ionospheric dynamics in regions where neutral wind control is weak.

On May 10, 2024, the Earth’s geospace system and existing models were pushed to their limits by the largest geomagnetic storm in two decades. While the resulting auroras were a global spectacle, the underlying physics revealed a system undergoing a rapid and large-scale structural reconfiguration. This talk explores the science of this extreme event across the whole geospace system, emphasizing how the ionosphere responded to these unique drivers. By examining the magnetospheric and upper atmospheric responses together, the complex coupling and energy exchange between these regions become clearer. These observations demonstrate the necessity of a coupled whole geospace approach to analyze how these systems communicate and what happens when that global conversation turns into a shout.
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Accurately diagnosing and characterizing plasma dynamics in laboratory experiments and space plasmas is essential for advancing basic plasma science. Modern high-repetition-rate
experiments and multi-spacecraft missions provide increasingly rich spatiotemporal measurements, but computational tools that can fully exploit sparse, noisy, and incomplete data
remain lacking. Physics-informed neural networks (PINNs) offer a promising route by combining partial measurements with fundamental plasma equations to reconstruct physically
consistent quantities that were not directly measured.
In this talk, I will illustrate this approach using shear Alfvén waves, a fundamental mode of magnetized plasma that transports electromagnetic energy along magnetic fields and is relevant
to auroral energy flow [1]. Using synthetic magnetic-field measurements from fully kinetic particle-in-cell simulations, we show that PINNs can reconstruct the full two-fluid plasma
state—including electric fields, ion and electron velocities, and density perturbations—from sparse magnetic-field data alone. The method achieves approximately 10% relative accuracy
under adequate sampling and remains robust to substantial measurement noise.
I will then discuss first applications to experimental measurements of shear Alfvén waves on the Large Plasma Device at UCLA [2], including challenges posed by real data. Finally, I will briefly
outline how this framework could be extended to multi-spacecraft observations, where detailed measurements of the magnetic-field and the plasma distribution function are available but very
sparse.

Parker Solar Probe is revolutionising our understanding of turbulence in the solar wind and corona. The “standard model” of anisotropic, low-frequency Alfvénic turbulence predicts little ion heating, because the magnetic moment is conserved to all orders in the low-frequency expansion. This is in stark contrast to the observed dominance of perpendicular ion heating in the corona and low-beta solar wind.
In this talk, I present a new theoretical picture of perpendicular ion heating that unifies previous models of stochastic heating, cyclotron heating, and heating in guide-field reconnection. An important advantage of this new model is that it is easy to apply to intermittent turbulence. I demonstrate that accounting for rare, large-amplitude coherent fluctuations, naturally produced by the turbulent dynamics, can dramatically enhance the predicted efficiency of ion heating, resolving the previous discrepancies between theory and space measurements. This suggests that intermittency is not just a statistical curiosity, but a necessary component of any theory purporting to describe heating in plasma turbulence.

Large language models, and the agents built on top of them, are beginning to change how research is done, yet the core ideas remain unfamiliar to many scientists. In this talk, I will explain them from the ground up, assuming no prior background: what a large language model is, what an AI agent is, and what an “agent harness” — the tools, memory, and feedback loop that turn a passive model into something that can act — actually does. I will then turn to why this matters for Earth and space sciences, where reaching a scientific result often means first spending months learning each mission’s data formats and conventions, and describe an effort to build a shared, community-owned skill repository that lets agents handle this competently across subfields. The broader argument is that agents are poised to transform not only everyday scientific work but how people work more generally — and that building the right scaffolding now is what determines whether that promise is realized.

The eleven-year solar activity cycle manifests itself in a variety of spectacular and interdependent ways. For example, the spatiotemporal distribution of the emergence of bipolar active regions (ARs) impart a spatiotemporal dependence to the response and re-configuration of overlying large-scale, closed-flux helmet streamer belt. Additionally, specific AR–background field configurations can arise that form new, intermediate-scale closed-flux systems surrounded by single polarity open fields, such as coronal pseudostreamers, which also inherit the underlying solar cycle-dependence of their photospheric flux distributions. The global magnetic structure of the solar corona, in turn, determines the entire solar wind stream and magnetic sector structure of the inner heliosphere. The cusp region of the coronal helmet streamer belt extends into a dense, slow solar wind plasma sheet that contains the heliospheric current sheet (HCS), separating the open fields of opposite polarity. The equivalent heliospheric extension of pseudostreamer outflows along the outer spine-line or spine-fan, result in slow, plasma-sheet like solar wind embedded in a single open field polarity.
In this talk , I will present an overview of the ways in which coronal magnetic field topology, open-closed flux system boundary layers, and their dynamic evolution can determine the resulting solar wind properties and structure of the inner heliosphere. As an illustrative example, I will discuss recent remote-sensing and in-situ observations made by Parker Solar Probe (PSP) in the context of the Casillas et al. [2026] magnetohydrodynamic simulation results. For example, the PSP Encounter 24 observations appear to have captured certain aspects of the Casillas et al. scenario of a global-scale pseudostreamer–to–helmet streamer transition and the generation of outflow transients associated with the opening-up (and closing-down) of a large-scale pseudostreamer flux system which creates (or destroys) the parasitic-polarity solar wind streams and their associated HCSs.

Magnetopause magnetic reconnection during periods of northward interplanetary magnetic field (IMF) plays a key role in the entry of solar wind mass into the magnetosphere. The effects of reconnection can be observed in the low-altitude cusp, and the new NASA TRACERS mission is designed for this purpose. I will present a TRACERS-THEMIS conjunction near the peak of a geomagnetic storm after the IMF had turned northward. In the low-altitude cusp, TRACERS observed signatures consistent with lobe reconnection poleward of the cusp, including reversed ion dispersions and sunward convection. Concurrent THEMIS observations at the low-latitude magnetopause reveal the presence of a magnetosheath boundary layer (MSBL) and capture of magnetosheath plasma on magnetospheric field lines, both consistent with poleward-of-cusp reconnection. Global simulations of the event show that poleward-of-cusp reconnection was adding magnetic fields and plasma to the magnetosphere, and in the process moving the cusp poleward. The event also illustrates how the magnetosphere and cusp recover when the IMF turns northward after a storm has eroded the magnetopause inward and moved the cusp equatorward.

Jupiter’s moon Europa is a key target in the search for extraterrestrial life, but assessing its habitability via magnetic induction requires a well-grounded understanding of the plasma environment. At Europa, this task relies on magnetohydrodynamic (MHD) models that have been developed over many years. While powerful, these models are computationally expensive, with some codes requiring > 12 hours on a 2,000-core machine. Fitting spacecraft observations to MHD models demands many runs, resulting in a potentially days- or weeks-long process. This presents a major bottleneck for missions such as Europa Clipper and JUICE, potentially limiting their scientific return.
In this talk, I introduce a transformer-based surrogate for a state-of-the-art MHD model used to help characterize Europa’s subsurface ocean. The surrogate evaluates in milliseconds on a laptop rather than hours on a supercomputer, achieving a speed-up of approximately 40,000x while delivering high-fidelity, uncertainty-aware magnetic field predictions. This acceleration enables three new scientific pathways that are feasible with MHD alone: large-scale parameter surveys, simulation-based inference, and feature-importance analysis. These analyses are important as the environment is poorly constrained observationally. Overall, this approach represents a paradigm shift in the investigation of space plasmas and opens the door to a host of novel science investigations.

NASA science missions are often complex systems of systems, involving various stakeholders, including the United States’ Congress. To ensure a clear and concise communication of expectations, requirements, and constraints, NASA has adopted the Science Traceability Matrix (STM). STM provides a logical flow from the decadal survey to science goals and objectives, mission and instrument requirements, and data products. STM serves as a summary of what science will be achieved and how it will be achieved, with a clear definition of what mission success will look like. In this seminar, I will present the STM from the Parker Solar Probe (PSP), including requirements relating to the plasma instrument for which I am a co-investigator. I will describe how our team used the STM to map the mission’s top-level requirements to mission success criteria and helped to eliminate any single point of failure that could end the mission prematurely. I will then present my own research on magnetic switchbacks in the PSP magnetic and plasma observations and their role in solar wind acceleration and heating. I will conclude the seminar by discussing how my research on the temporal evolution of switchbacks in the solar wind led to a new STM, and helped to chart a multidisciplinary path to designing a ground-breaking science mission concept, titled Space Weather Investigation Frontier (SWIFT), with the potential to improve space weather forecasting lead times by up to 40%.

Extraterrestrial EM induction was first carried out in the 1970s
by forming magnetic transfer functions for the Moon as the ratio of
magnetic fields observed at the surface (Apollo 12) to those observed in
distant orbit (Explorer 35). In March 2025, a similar analysis was
performed using the Lunar Magnetotelluric Sounder (LMS) on Blue Ghost
Mission 1 and the ARTEMIS spacecraft. In spite of nearly 90 deg arc
distance between these surface locations, the derived subsurface
conductivities are very similar. This sharply limits contemporary
temperatures under the western nearside of the Moon in spite of its past
history of widespread volcanism. The two-week surface mission recorded
surface electric and magnetic fields in the solar wind, magnetosheath, and
magnetotail, including an eclipse and sunset. Plasma properties correlate
well with ARTEMIS.

Mars’ lack of a global magnetic field led to low expectations for auroral phenomena on the planet, but MAVEN and Emirates Mars Mission observations have unexpectedly shown auroral activity to quite diverse in nature, dynamically varying and often global in scope. The image below shows three fundamentally different types of aurora on Mars. Ironically, Mars’ lack of a global field is actually responsible for most of the activity, which leads to a new perspective for non-magnetized objects in our solar system and beyond. Each of the three types of aurora is a tracer of a different important process involving the interaction between solar influences and the near-Mars magnetic and charged particle environment. The seminar will describe observations by MAVEN’s Imaging UltraViolet Spectrograph (IUVS) and the Emirates Mars UltraViolet Spectrometer (EMUS) and highlight the new insights they offer.

Space weather is the “weather” of the space environment driven by our active Sun—solar eruptions and changing solar wind conditions that can disturb Earth’s magnetic field and upper atmosphere, disrupt satellites and communications, degrade navigation and timing, increase radiation risk to astronauts, and induce electrical currents in long conductors on the ground. Over the past decade, U.S. preparedness for major space weather events has changed in two consequential ways: (1) the power sector began translating scientific risk into enforceable reliability practice when the Federal Energy Regulatory Commission (FERC) directed the North American Electric Reliability Corporation (NERC) to develop Reliability Standards to mitigate geomagnetic disturbance (GMD) impacts on the Bulk-Power System ; and (2) the United States adopted a coordinated, whole-of-government posture through the National Space Weather Strategy and Action Plan—now further advanced through a more recent federal implementation plan that builds on the 2015 foundation .

I will highlight key scientific and operational developments from the last few years, including NASA’s Space Weather Program role in advancing space weather observations, models, and applications that support prediction and tracking across the solar system. A central case study will be the May 2024 geomagnetic storm—first G5 (“severe”) storm in over two decades—now commonly referred to as the “Gannon storm,” and what it revealed about magnetosphere–ionosphere coupling, satellite impacts, and the pathways to societal consequences.

Finally, I will offer focused perspectives on high-impact risk areas—especially electric power grids—connecting space physics to practical resilience: where the key areas of uncertainty are, what “good enough” information looks like for operations, and how research, standards, and planning can converge to reduce national risk before the next extreme event.

Learn about ionizing radiation in the final frontier from UCLA Space Medicine Program Director Dr. Haig Aintablian and Radiation Oncology resident Dr. Nic Nelson. They will share a brief overview of modern space medicine and basic radiobiology before exploring the space radiation environment with its unique risks to astronaut health. They will then illustrate how researchers and mission planners are preparing for the next phase of human space exploration—interplanetary travel—by investigating different physical and biological countermeasures and applications in personalized medicine.

Solar radio bursts are signatures of nonthermal electron acceleration by energetic events such as flares and coronal mass ejections. The launches of Parker Solar Probe in 2018 and Solar Orbiter in 2020 have enabled new views of radio bursts from the vantage point of the inner heliosphere. In this talk, I will briefly discuss some of the top radio burst discoveries of the Parker-Orbiter era, with a focus on circular polarization observations made by Parker Solar Probe. I will describe the measurement of polarization using spacecraft antennas, show examples of circularly polarized Type II and Type III radio bursts, and discuss how polarization can serve as a remote diagnostic of radio burst source regions.

Galileo, Cassini and Juno space missions have provided much data on gas giant magnetospheres. Here we examine the important commonalities of the two systems that also characterise the differences to the plasma environment of the inner planets. Both systems are fast rotators and have internal sources of magnetospheric material deep within the system. The internal sources means there must be a system for transport of material outward. Commonly, marginally stable interchange motions of flux tubes are invoked to provide diffusion on relatively small scales transverse to the field. This no doubt occurs near the source but processes like self-organisation may lead to more ordered motion at larger distances. A large distinction between Jupiter and Saturn systems is that the jovian planetary magnetic field is far from axially symmetric with respect to the planetary rotation axis whereas Saturn’s field is close to axially symmetric. However, despite this, the Saturn system does exhibit variable periodicities in plasma, radio, aurora and the external magnetic field around 10.7 hours. The external magnetic source was a surprise; the ubiquitous Saturn oscillations are still described as “mysterious”. No similar oscillations are recorded at Jupiter. We shall aim to remove some of the mystery and suggest that the dynamical effect of rotation has not been fully appreciated in either system.

Prediction serves as the ultimate test of our scientific understanding of geophysical systems. Accurate forecasting of near-Earth space environmental conditions is critical to radio communication, navigation, and space traffic management. Effective numerical prediction of the region’s conditions allows us to better protect important space assets and related systems in the event of natural hazards. My research group aims to advance the science and engineering of forecasting, as applied to the Earth’s atmosphere extending from the ground to geospace. Prediction of the constantly changing near-Earth space environmental conditions – affected by both space and terrestrial weather – is inherently challenging. Data assimilation provides a systematic approach to integrating observations with first-principles models, extending the predictive capability of numerical models by reducing uncertainties in drivers and preconditions and constraining model dynamics with observations. The data assimilation and ensemble-based probabilistic modeling framework can also be applied to the design of future missions and the targeting of observations to maximize scientific returns of observing systems. This seminar showcases some of the latest data assimilation research and outlines future plans, setting the stage a discussion on how we can work together to advance the next generation of predictive modeling and observational strategies.

Mars’ interaction with the solar wind exhibits a hybrid nature. The Martian magnetosphere, formed through interactions between the solar wind, ionosphere, and crustal magnetic fields, is complex and highly dynamic. While largely induced, it also contains localized regions where strong crustal fields dominate plasma dynamics. Global magnetohydrodynamic (MHD) modeling has become a critical tool for investigating this system and its role in atmospheric escape. Multi-species MHD studies first demonstrated the importance of ion-specific treatment at high spatial resolution, while later work revealed how rotating crustal fields modulate plasma boundaries and ionospheric structure. Applications to extreme events, such as the September 2017 ICME and the December 2022 disappearing solar wind event, highlighted the dynamic response of Mars’ plasma environment to solar wind variations, particularly density changes. This seminar will review advances in global MHD modeling of Mars and discuss their implications for understanding atmospheric escape and developing future space weather forecasting capabilities at the planet.

The Polarimeter to Unify the Corona and Heliosphere (PUNCH) is a constellation of four smallsats launching in Spring 2025 to image the solar corona and solar wind as a single unified system. The four satellites work together to form a single “virtual coronagraph” with a 90° field of view centered on the Sun. One satellite carries a coronagraph (the Narrow Field Imager) that captures the outer corona at apparent distances between 6 solar radii and 32 solar radii from the Sun. The other three carry heliospheric imagers with 42° wide fields of view, extending from 12 solar radii to 180 solar radii from the Sun. All instruments view visible light scattered by free electrons in the corona and solar wind and use linear polarization to generate 3D information about density structures in the plasma. In this talk, I will briefly describe some of the key background science and the mission itself, then discuss the enabling technologies of deep signal separation and polarimetric inversion to reveal 3D structure before presenting and discussing recent data from the constellation and how to obtain the data for your own use.

Space is never empty. Instead, it is filled with high-energy particles originating at the Sun and trapped by Earth’s magnetic field, forming dynamic radiation environments that pose significant risks to satellites, astronauts, and future exploration missions. In this talk, I will discuss the evolution of Earth’s radiation belts during geomagnetic storms, the processes that limit their intensity, and how similar processes may operate under artificially created conditions. I will present recent work on fast plasma processes that substantially alter radiation levels around Earth. My approach integrates data analysis, simulations, and the development of advanced particle detectors derived from technology originally designed at CERN, tailored specifically for space missions. Additionally, I will showcase results from a student-led balloon mission conducted during the most intense geomagnetic storm of the past two decades. 

Earth’s outer radiation belt is a doughnut-shaped region in space, containing stably trapped energetic electrons. Its outer boundary is closely related to the electron isotropy boundary (IB), which separates the outer radiation belt from the isotropic, precipitating electrons found further out, in the tail current sheet. Field-line curvature scattering (FLCS) is believed to play an important role in causing this isotropic electron precipitation and is effective when the electron gyroradius becomes comparable to the field line curvature radius in the equatorial current sheet region. However, the direct and quantitative impact of FLCS in controlling the outer belt electron lifetimes has never been directly assessed. In this talk, I will discuss the role of FLCS in controlling the outer belt electron lifetimes by combining observations and global radiation belt electron simulations. I will also reveal that this simple yet fundamental physical process which has been historically neglected in global radiation belt models, is sufficient to explain the outer electron belt configuration. Our findings transform our understanding of the dominant processes controlling radiation belt dynamics.

Jupiter’s moon Europa is thought to possess a subsurface ocean that could have the right conditions to harbor life. It will be visited by the Europa Clipper mission starting in 2030. To characterize this ocean and answer questions about habitability, the complex and highly variable plasma environment must be accounted for. In this talk, I will introduce a novel machine learning framework, including both forward and inverse modeling, to better understand the environment. Crucially, our model can reproduce the magnetic field, helping us define the depth, salinity, and conductivity of a potential subsurface ocean. These findings benefit both the upcoming missions to Europa and proposed missions to other planetary bodies such as those at Uranus or Neptune.

Magnetic reconnection occurs continuously along long X-lines at the Earth’s magnetopause. The maximum magnetic shear model provides accurate predictions for the locations of these long X-lines for a wide range of upstream solar wind conditions. One of the more perplexing observational results is that these X-lines appear to be stationary, even on the near-flank magnetopause in the presence of significant magnetosheath plasma bulk flow. An alternate possibility is that X-lines form in the location predicted by the maximum magnetic shear model but then immediately propagate with the magnetosheath plasma bulk flow away from this location. If the X-line reformation cadence is high enough and some other conditions are valid, then these multiple propagating X-lines could appear as a single quasi-stationary X-line at the location predicted by the maximum magnetic shear model. Magnetospheric multiscale observations are used to perform initial tests of this alternate possibility. Results from these initial tests show that there may be multiple X-lines near the predicted location of the X-line, and therefore this alternate possibility may have merit. This alternate possibility may have implications for the magnetospheric cusps. Magnetic reconnection at the magnetopause produces distinct energy-latitude ion dispersion features in the cusps. Multiple reconnection X-lines may produce overlapping dispersion features depending on how they are formed. Therefore, under the right solar wind conditions, there may be many instances of overlapping dispersion features. Observations from the Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) are used to investigate this possibility.

Magnetosphere and ionosphere coupling is largely driven by electromagnetic waves (e.g., Alfven waves) and particle precipitation in the polar cusp and auroral region. This coupling is inherently dynamic, nonlinear, and multiscale. Ionosphere magnetic perturbations (δB) span scales from >1,000 km across the auroral zone—associated with Region-1 and Region-2 field-aligned currents (FACs)—down to <1 km, approaching the electron inertial length and corresponding to fine-scale auroral arcs (~100 m). These smaller scale δB are often linked to inertial Alfven waves that carry parallel electric fields, accelerate electrons, and produce dynamic auroral structures. During geomagnetic storms and substorms, transient currents associated with these small-scale δB can exceed several hundred μA/m2, leading to ionosphere total electron content (TEC) perturbations and plasma irregularities that cause GPS scintillations and disrupt communication. Characterizing these small-scale δB and their space weather effects remains challenging due to Doppler shift from spacecraft motion (~7.8 km/s) and the scarcity of tandem spacecraft observations of electric and magnetic field measurements necessary to distinguish DC and wave components. NASA's TRACERS mission, launched on 24 July 2025, offers new opportunities to investigate these processes. Here we present initial results from TRACERS MAG observations of a coincident small-scale δB and GPS scintillation event.

The Low-Latitude Ionosphere/Thermosphere Enhancements in Density (LLITED) mission consisted of two 1.5U CubeSat to study nighttime ionosphere/thermosphere coupling. Each CubeSat hosts three science payloads: an ionization gauge (MIGSI) to observe neutral density, a planar ion probe (PIP) to observe plasma density, and a GPS radio occultation sensor for observing (CTECS-A) total electron content. The overall mission, from proposal to on-orbit operations and science investigations, has presented a number of challenges often requiring difficult decisions and compromise in order to maximize the science returns. The various orbit and technical difficulties necessitated a modification and reprioritization of LLITED’s science mission objectives. By modifying the mission science goals, prioritizing event-associated observations, and combining data from other missions and observational conjunctions, LLITED provided insightful observations of neutral and plasma density structures and coupling. This presentation will provide an overview of LLITED’s datasets, describe the various on-going studies, and highlight observations of neutral and plasma density structures at high and mid- latitudes, as well as observations of short time stability of small-scale density structures.

Alfvén waves, named after the Nobel laureate Hannes Alfvén, are a fundamental mode in magnetized plasmas. It has long been established that they play a key role in the energy circulation of the magnetosphere-ionosphere (M–I) coupling system. However, their dissipation on meso- and small-scales is much less well understood. Here, we examine how Alfvén waves drive several common meso-scale structures, including the auroral arcs, auroral beads, and the magnetospheric cusp. We find that Alfvén waves, although being the common energy source, are dissipated differently among these structures. In the auroral arcs, Alfvén waves power a quasi-static parallel electric field that accelerates ions away from and electrons toward the ionosphere. In the auroral beads, electrons are accelerated directly by the wave’s own parallel electric field. In the cusp, Alfvén waves significantly energize the outflowing ions, presumably through perpendicular heating. These distinct energy conversion processes we have unveiled are important in understanding the meso-scale M–I coupling on Earth and other planets. Our results also raise important questions for future studies: How are these Alfvén waves generated? What additional dissipation mechanisms may be operating? Why are Alfvén waves dissipated differently, and what are the controlling factors?

Venus and Earth are often described as planetary “twins”; however, the large-scale volcano-tectonic surface features on each body indicate a different interior state and suggest that somewhere in their evolutions, they diverged. Certain features that represent a surface manifestation of the mantle convection within Venus show a “plume-thermal dichotomy”: large-scale mantle upwellings (plumes) appear to coexist in both space and time with many more small-scale mantle upwellings (i.e., thermals). How can we explain this coexistence of multiple scales (~100 km vs ~1000 km) of mantle convection on Venus, and why do these smaller-scale convective features, called coronae, not appear on the surface of the Earth? This talk will discuss the role that mineral phase transitions may play in the mantle convective dynamics of present-day Venus. The talk will also discuss the role that changes in mineral phase transitions may play in the long-term thermal evolution of terrestrial planetary bodies like Earth and Venus.

The surface of Mars once hosted flowing liquid water and a warmer climate than today, with past water-rock interactions recorded by the carbonate deposits found on its surface. This work explores the depositional setting of the Margin unit, a major Mg-carbonate deposit near the fluvial inlet to Jezero crater, using ground-penetrating radar data collected by the NASA Mars 2020 Perseverance rover’s Radar Imager for Mars Subsurface Experiment (RIMFAX) instrument. Soundings are reported from more than 35 m below ground, ~1.75 times deeper than other Jezero geologic units explored to date. We identify numerous subsurface features and submeter to hundred-meter scale layering across a ~6.1-km rover traverse. We infer that subsurface reflectors are consistent with buried fluvial features that have undergone multiple erosional-depositional episodes. This work extends the known history of aqueous activity within Jezero crater. It illuminates a well-preserved paleo landscape wherein a deltaic environment developed before the formation of the Jezero Western Delta, as early as the Noachian (~4.2 to 3.7 billion years ago).

Earth’s only natural satellite, the Moon, orbits our planet at about 239,000 miles (385,000 kilometers, or ~60 Earth radii). Each month, it spends about 3–4 days passing through the nightside of Earth’s magnetosphere — the magnetotail. Far from Earth, the magnetotail has a weak, highly variable magnetic field and strong spatial gradients. This makes it a natural laboratory for studying magnetic fields and charged particle interactions under conditions opposite to those in the dipole-dominated inner magnetosphere. Using observations from two ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun) spacecraft, orbiting the Moon on elongated, near-equatorial (~100 km × 19,000 km) trajectories, we examine the near-Moon magnetic field and plasma properties under varying space weather conditions. We find that during quiet times, the plasma properties in the distant lunar magnetotail are largely controlled by the energy of the solar wind, and high-energy particles are rare. During active periods, however, we observe bursts of very energetic – sometimes even relativistic – ‘killer’ electrons near the Moon. Our results suggest that these electrons were energized within the magnetotail itself, although the exact mechanisms remain unclear.

This work integrates spatiotemporal datasets in California over a twenty-year period (2003-2023) to identify links between anomalies in fecal indicator bacteria (FIB) — Escherichia coli, total coliforms, fecal coliforms, and Enterococcus — at coastal areas and the occurrence of recent wildfires. Average FIB concentrations, land cover, precipitation, and burn histories are quantified with available data for every month across all watersheds flowing into the California Coast. Monthly non-burn background FIB concentrations are calibrated in coastal areas. FIB anomalies that are statistically distinct from these background levels are identified for both burn periods (>10% of the watershed burned within a two-year window) and non-burn periods and are reported as the anomalous FIB concentrations normalized by the background concentrations. Correlations between FIB anomalies and monthly precipitation and land cover fractions are identified by comparing data from all watersheds impacted by large fires. During burn periods, anomalous total coliform concentrations relative to baseline values (anomalies) exhibit a negative correlation with urban and positive correlations with coastal oak woodland, mixed chaparral, and redwood land cover fraction and monthly precipitation. Fecal coliform anomalies exhibited a positive correlation with urban land cover fraction after fires. Results indicate prominent post-fire export of total coliform bacteria (perhaps from decaying plant material and soils) in watersheds with less urbanization, and prominent export of fecal coliform bacteria from humans and animals in urbanized watersheds to coastal waters. This is the first effort to generalize post-fire FIB responses in coastal waters. The results may inform future risk assessments and proactive measures.

Early atmospheric chemistry and climate play an important part in what worlds have liquid water and how life could emerge, but preserving evidence for this over geologic time often presents a challenge. Compared to Earth, which undergoes continuous erosion by plate tectonics, Mars offers a superb window into its earliest history, preserved right on its surface, and is therefore an excellent case study for planet evolution. What we learn here can extend to other planets in the solar system, the early Earth, Venus, and even outside the solar system at exoplanets.

Extensive surface evidence suggests Mars once hosted large volumes of liquid water, implying a warmer climate sustained by a thicker atmosphere than present day. Previous studies propose that CO2-dominated atmospheres enriched with H2 or CH4 could have driven warming, though such gases exhibit short atmospheric lifetimes. This talk will first present a novel explanation for sustaining warm climates up to 40 million years: hydrogen release through crustal hydration. Evidence of atmospheric climate and redox transformations may remain preserved on the surface and in meteorites. To test our hypothesis, we show that deposits measured by Mars Science Laboratory and isotopic fractionation measured in meteorites can both be explained photochemically under specific climates and atmospheric redox states. We also present predictions of isotopic signals under different climate and redox states that Mars Sample Return missions should search for.

Like Mars, Venus may have also experienced large climate changes during its evolution too. Modern Venus is a hot, arid environment, yet the possibility of an early cool, habitable phase remains unresolved. The talk will explore when sulfuric acid hazes in Venus’ history could have sufficiently cooled the planet to allow surface rainfall. This scenario may be testable using NASA’s upcoming Habitable Worlds Observatory (HWO), which will observe exoplanets with Venus-like characteristics.

While HWO’s launch lies years ahead, exciting exoplanet data have already been measured with JWST, Hubble, and Spitzer. When we observe planets also influences their chemistry, and the presentation will explain a new hypothesis for missing methane at warm Neptunes. The talk also highlights ongoing efforts to develop modeling tools to interpret future data, including microphysics and 3D dynamics. These analyses aim to refine atmospheric interpretations and advance our understanding of planetary evolution across diverse environments.

Laboratory tank experiments have long served as simplified analogues for planetary fluid dynamics, offering a controlled way to isolate the effects of rotation and external forcings. Although no laboratory setup can reproduce the full complexity of a planet, such experiments can successfully capture the dominant dynamical balances that govern large scale geophysical flows. In this talk, I discuss how tank scale experiments reflect key aspects of planetary fluid dynamics at a conceptual level, with emphasis on what is gained—and what is lost—through this reduction in scale and geometry.

Large-scale flows in gas giant atmospheres, icy moon subsurface oceans, and liquid planetary cores control the transport of heat and chemical species, as well as the generation of magnetic fields in electrically conducting fluid regions. Understanding these fluid systems fundamentally depends on our ability to predict the variety of dynamical length scales that arise from the interplay of rotation, buoyancy, and planetary curvature. These ingredients are simulated in UCLA’s Coreaboloid, a rotating convection device equipped with an infrared (IR) camera aimed axially downwards at the free surface of the fluid. IR-derived surface temperature fields function much like the clouds in Jupiter’s weather layer, revealing the multi-scale dynamics of the rapidly-rotating flow. The small scales in the temperature field are dominated by eddies generated through rotating convection and baroclinic instabilities. Kinetic energy injected through these processes feed into east-west Jovian-like jets, which saturate at large scales set by friction. This alternating pattern of zonal flows influences the transport of heat, producing bands of matching width in the temperature field, reminiscent of Jupiter’s stripes. Complemented by particle image velocimetry, the IR-derived temperature data provide the first match between observed and predicted convective, baroclinic, and jet length-scales coexisting in laboratory experiments of rotating convection with multiple coherent jets.

GPS measurements of the vertical motion of Earth’s surface along with gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow On (GRACE-FO) missions provide valuable data to analyze changes in terrestrial water storage (TWS) as a function of position and time. These integrated datasets effectively quantify TWS variations across global and regional scales. Here we expand upon previous studies that have incorporated GPS and GRACE(-FO) to determine long-term water cycle changes in the United States, by applying similar methodologies to provide one of the first looks into water cycle changes throughout Europe. Through applying a standard list of processing steps, we filter out unwanted signals in GPS measurements of vertical ground motion and identify GPS stations in Europe measuring only elastic displacements. By analyzing these elastic GPS displacements alongside GRACE(-FO) inferred data, we identify local and regional water cycle trends over the past 23 years, offering crucial insights into Europe’s hydrological evolution.

Between 2010 and January 2025, California’s western Transverse Ranges experienced 18 fires with burn areas larger than 20 km2, the largest of which was the ~1141 km2 Thomas Fire, which burned across Ventura and Santa Barbara Counties in December 2017. During the same period, this area occasionally experienced unusually wet seasons with several landfalling atmospheric rivers. The most notable was the 2022-2023 atmospheric river season, which saw significantly elevated precipitation totals relative to the 30-year average and which triggered widespread landslides and debris flows in burned hillslopes across Southern California. Terrain, cloud cover, and vegetation cover complicate comprehensive range-scale post-atmospheric river surface disturbance mapping and monitoring. We created a supervised threshold-based NDVI (normalized difference vegetation index) change detection to map surface disturbances. We then run a frequency ratio-based susceptibility model using confirmed landslide heads. We applied these models to the eastern Santa Ynez Mountains northwest of Ojai, CA, on terrain burned by the December 2017 Thomas Fire and affected by the January 9, 2023 atmospheric river, to better understand the relationship between local topographic factors, landslide triggering, and extent of downstream sedimentation. We considered eleven different parameters at 250 landslide heads in (distance to channel, eastness, elevation, northness, plan curvature, profile curvature, roughness, sediment transport index, slope, and stream power index, and topographic wetness index). Of these, we found the three most statistically relevant metrics in our study area were plan curvature, topographic wetness index, and distance to channel.

Stars of all sizes and ages are plagued by “missing mixing problems,” or discrepancies between stellar models and observations that indicate some unknown turbulent mixing occurs in their interiors. The precise nature and degree of this anomalous mixing can hold major consequences for the fates of such stars, their spins, and their chemical makeup over time. I will discuss a particularly ubiquitous mixing problem in red giant branch stars—a widely observed class of star that our own sun will eventually become. The leading candidate to explain the missing mixing in these stars is salt-finger (or “thermohaline”) convection, a form of turbulence also found in tropical oceans. I will show that the dynamics of salt fingers in stars are often surprisingly similar to oceans (despite the enormous difference in fluid properties between stellar plasmas and salt water) except when magnetic fields are present. In such cases, magnetic fields dramatically enhance the turbulent mixing rate, potentially solving this long-standing missing mixing problem.

Atmospheric compositions of sub-Neptunes and super-Earths are often interpreted as tracers of formation history and volatile delivery. However, many of these planets likely experience long-lived magma-ocean phases during which their atmospheres can chemically equilibrate with a molten silicate interior. In this talk, I will show how magma-ocean–atmosphere interactions reshape atmospheric compositions and alter observable signatures. Using a global chemical equilibrium framework, I demonstrate that key abundance ratios such as C/O and H2O are not simply inherited from disk accretion, but can be substantially modified by interior processing. This has important implications for the interpretation of apparently water-rich worlds, which may in fact be significantly drier than predicted by previous models. I will also present new extensions of the model including sulfur and nitrogen chemistry, which provide additional diagnostics of volatile redistribution between atmosphere and interior and further strengthen the connection between interior evolution, atmospheric composition, and spectroscopic observations.

Giant impacts are the last major stage in the formation of terrestrial planets. They also are believed to play a major role in the assembly, long-term orbital stability, and resonant structure of exoplanetary systems. Both the mechanical shock and thermal heating of a giant impact can cause atmospheric mass loss. Previous works have shown that for planets with hydrogen-dominated atmospheres, the post-impact thermal heating acts as the dominant mass loss mechanism by inflating the planetary envelope and driving a Parker wind. However, past studies have considered the atmosphere and interior of these planets as discrete, non-chemically-interacting layers. We revisit this idea through the lens of a coupled atmosphere-interior system, allowing for chemical interactions between the core and envelope as the planet experiences heating and subsequent cooling after a giant impact. Considering a miscible interior affects the mean molecular weight of the envelope, allows hydrogen to mix into the core, and modifies the compositional gradients in the planet, thus altering the atmospheric mass loss. We present new results for the atmospheric loss due to giant impacts and discuss their implications for the formation and composition of super-Earths, sub-Neptunes and the radius valley.

The Main Belt is a region lying between Jupiter and Mars that contains a vast number of small bodies ranging in both size and shape. Until the 1990s, it was believed that the Main Belt consisted primarily of asteroids. However, the observation of 7968 Elst–Pizarro (133P/Elst–Pizarro) in 1996 by Eric Elst and Guido Pizarro, along with the work of Jewitt and Hsieh in the early 2000s, led to a new classification of small bodies: Main Belt Comets (MBCs). These comets – later deemed a subset of Active Asteroids – exhibit circular, asteroid-like orbits with semi-major axes 𝑎 < 𝑎_J, but maintain comet-like characteristics such as a coma, tail, or 𝐽𝑢𝑝𝑖𝑡𝑒𝑟 visible mass loss. Since their initial discovery, MBCs have been inadvertently observed throughout the Main Belt, and many have attempted to put constraints on their number density. A 2013 study by Waszczak and others placed upper limits of 33 and 22 active MBCs per million main-belt asteroids down to∼1-km diameter (Waszczak et al, 2013). A more recent study in 2022, by Ferellec and others, deduced a MBC-to-asteroid ratio of <1:500 (Ferellec et al. 2022). For this study, we plan to utilize the data from the WISE/NEOWISE survey to search for MBCs. WISE/NEOWISE is a space-based wide-field infrared telescope that surveyed MB small bodies over the past ten years. The mission’s objective was to identify near-earth objects (NEOs) and MBAs; thus, it has not been analyzed for MBCs. A thorough search of this data set should yield a number of MBCs which can then be used to place constraints on their number density in the Main Belt.

The Pacific Ocean covers a large portion of the Earth’s surface. However, seismic constraints on its crust and upper mantle structure remain limited due to sparse station coverage. Ambient noise tomography provides an effective approach to improving spatial coverage by extracting empirical Green’s functions (EGFs) between station pairs, while also offering enhanced vertical constraints on crustal structure. In this study, I use continuous seismic data from both land-based stations and ocean-bottom seismometers (OBS) to measure Rayleigh wave group and phase velocity dispersion across the Pacific region, targeting the period 1990–2025. Preliminary results based on the 2005–2006 datasets demonstrate that reliable dispersion curves can be obtained for station pairs at appropriate interstation distances over a period range of 5–50 s. Ongoing work focuses on incorporating additional years of data and improving signal quality, particularly for OBS records, to enhance path coverage and support future tomographic imaging of oceanic structure.

The Mendocino Triple Junction is in a tectonically complex region where a multitude of physical mechanisms contribute to crustal deformation. To discern these physical drivers, our group (1) enhanced the Northern California Seismic Network (NCSN) earthquake catalog spanning the 2022 Ferndale and 2024 Offshore Cape Mendocino sequences using machine learning and template matching approaches, (2) extended a repeating earthquake catalog to study the contribution of aseismic slip to both earthquake sequences (3) analyzed changes in groundwater levels during the both sequences. In this talk, I will present our enhanced catalogs, which reveal ~5-10 times more events than the NCSN catalog, with a clear concentration of seismicity at the edges of the 2024 sequence’s coseismic slip patch. Additionally, I will highlight our study’s evidence for accelerating afterslip in the weeks following the 2024 sequence, and an elastic strain mechanism to explain the observed groundwater level changes.

Wildfire fundamentally alters hillslope and channel sediment transport by rapidly mobilizing dry ravel, which accumulates in channels immediately following burning and is subsequently flushed during the first post-fire rainfall. Using repeat high-resolution topographic surveys and channel-scale swath analyses within the Palisades burn scar, we examine how first-flush sediment storage and redistribution relate to channel steepness (k_{sn}) and underlying lithologic gradients. The Palisades wildfire provides a natural laboratory to examine these dynamics, as the study area spans a pronounced east–west lithologic gradient associated with systematically increasing channel steepness. We show that post-wildfire sediment transport and hillslope failure can be partitioned into two coupled but distinct processes: (1) dry ravel production, which occurs exclusively in steep, high-k_{sn} lower-order channels, and (2) precipitation-driven mobilization and redistribution of this material into channel trunks during early storm events. Dry ravel does not accumulate ubiquitously across the drainage network, but is instead restricted to channels that exceed a critical steepness threshold, indicating a strong topographic control on post-fire sediment supply. We further demonstrate that dry ravel accumulation in steeper lower order channels is spatially coincident with active scouring of the underlying channel bed, leading to sediment budgets that exceed existing infrastructural design capacities. Following rainfall, dominant patterns of erosion and deposition are negatively correlated with k_{sn}: deposition dominates in low-k_{sn} reaches, while high-k_{sn} channels experience net erosion and sediment export. Together, these observations suggest that first-flush sediment response following wildfire is governed not only by burn severity and rainfall intensity, but also by broader lithologic and topographic controls that regulate transport efficiency, sediment storage, and channel–hillslope coupling.

Static, long-term deformation generated by earthquakes provides essential constraints on fault slip, stress redistribution, and crustal rheology. However, measuring earthquake-induced static deformation remains challenging, particularly for moderate earthquakes, due to their small strain amplitudes. Traditional geodetic observations, such as high-frequency Global Navigation Satellite System (GNSS) and tiltmeter measurements, are susceptible to noise and limited in spatial resolution. Fortunately, Distributed Acoustic Sensing (DAS) offers a novel technology by converting pre-existing optical fiber into thousands of dense strain sensors, enabling high-resolution observations over large areas. This approach has been successfully applied to monitor static deformation associated with magma migration in volcanic systems.
Here, using DAS data from the Taiwan Milun Fault Drilling and All-inclusive Sensing (MiDAS) project, we demonstrate that static strain from more than a dozen aftershocks (Ml > 5) following the 2024 Mw 7.4 Hualien earthquake can be clearly recorded. Interestingly, at short spatial scales (~100 m), the strain field exhibits complex patterns, with even alternating extensional and compressional signals. Through numerical simulations, we hypothesize that this phenomenon is linked to anomalies in the medium’s Poisson’s ratio, which is consistent with the fractured structure of the Milun Fault. Overall, our results highlight DAS as a reliable complement to conventional geodetic observations, offering a useful tool for investigating seismic deformation fields.

Quantifying spatiotemporal dynamics of landslides, including occurrence, reactivation, and timing, is critical for understanding hazard risk in steep mountains. However, in regions like the Eastern Himalayas, mapping these spatiotemporal patterns is heavily restricted by persistent cloud cover, land-cover variability, and a scarcity of historical ground-truth inventories. To overcome these data and observational limitations, we utilized a novel unsupervised machine learning framework—the Stable Diffusion Change Detector (SDCD)—to extract continuous surface disturbance records directly from time-series optical satellite imagery. By bypassing the limitations of traditional manual labeling, this approach allows us to generate high-resolution landslide inventories in a data-scarce, cloud-prone region. Applying this method, we identify ~300 surface disturbance events, including landslides in hillslopes and channel-adjacent regions, over 1300 km2 and 10 years. We investigate temporal triggering of these events by analyzing daily precipitation and spatial patterns by comparing environmental conditions, including precipitation, long-term erosion rates, and topographic slope. Our time-series analyses indicate that abundant landslides in frontal basins are directly related to the magnitude of daily precipitation events, and the spatial density of overall landslides is highly consistent with independently measured long-term erosion rates. These results highlight the importance of high-resolution landslide datasets, both spatially and temporally, for understanding the complex controls on landscape change over time.

Being able to image the ruptures of moderate earthquakes would significantly increase our observations towards comprehending earthquake source physics, fault properties and seismic hazards.

However, resolving their rupture characteristics remains challenging for conventional seismic networks due to limited station density. The emergence of Distributed Acoustic Sensing (DAS) offers a potential solution by providing dense and continuous measurements. In this study, we systematically evaluate the resolution capabilities of multi-fibre DAS networks for back-projection (BP) and demonstrate the feasibility of using DAS networks through both synthetic tests and analysis of a Mw 4.9 event in the Eastern California Shear Zone.

Furthermore, we propose a two-step inversion procedure that strategically integrates DAS with the conventional network. Our results suggest that strategically deployed multi-fibre DAS network can serve as the next generation of earthquake observation system and significantly enhance our understanding of earthquake rupture physics, as well as seismic risk preparedness.

Numerical simulations of seismic wave propagation are crucial for investigating velocity structures and improving seismic hazard assessment. However, standard methods such as finite difference or finite element are computationally expensive. Recent studies have shown that a new class of machine learning models, called neural operators, can solve the elastodynamic wave equation orders of magnitude faster than conventional methods. Full waveform inversion is a prime beneficiary of the accelerated simulations. Neural operators, as end‐to‐end differentiable operators, combined with automatic differentiation, provide an alternative approach to the adjoint‐state method. State‐of‐the‐art optimization techniques built into PyTorch provide neural operators with greater flexibility to improve the optimization dynamics of full waveform inversion, thereby mitigating cycle‐skipping problems. We demonstrate the application of neural operators for full waveform inversion on real seismic data, using nodal transects collected across the San Gabriel, Chino, and San Bernardino basins in the Los Angeles metropolitan area. 

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Extreme weather and a warming climate can trigger cascading hazards that reshape landscapes and endanger infrastructure. This seminar explores how hydrology, climate, and geomorphology interact to cause or amplify land surface hazards, such as landslides, flooding, and permafrost degradation. By combining hydrologic modeling and remote sensing data, this work enhances understanding of the processes that link surface water, ground ice, and slope stability. The findings highlight the importance of interdisciplinary research in predicting and mitigating climate-related geohazards.

Groundwater renewability is a key factor in managing sustainable water resources in a changing climate. This seminar discusses new insights into groundwater age, flow pathways, and residence times across diverse aquifer systems. By integrating isotopic data and numerical modeling, the analysis reveals how recharge dynamics vary under different hydrogeologic settings. The results underscore the role of geologic structure and climate forcing in controlling groundwater sustainability and inform strategies for water management and policy.

The vast accumulation of carbon in Arctic soils—an estimated 1,700 Pg—has been referred to as a carbon bomb, a sleeping giant, and Pandora’s freezer. These terms all refer to the so-called ‘permafrost–carbon feedback,’ the cascading cycle in which warming temperatures destabilize permafrost soils, liberating large quantities of carbon to the atmosphere and driving further warming. But predicting whether Arctic landscapes will be a net source or sink of carbon requires tracking the transport and fate of the mobilized soil carbon and quantifying the strength of counteracting processes such as enhanced primary productivity of vegetation. I’ll show how the deposits of meandering rivers provide natural landscape-scale experiments that juxtapose frozen and thawed (permafrost and non-permafrost) terrain in the same environment, allowing us to track the changes to soil carbon and biomass reservoirs over timescales of years to millennia. These observations suggest that permafrost thaw may cause some Arctic landscapes to become a net carbon sink rather than a carbon source.

The deep sections of many modern subduction zones release strain through slow slip and tremor (SST), but the structures responsible, deformation mechanisms, and the role of syn-kinematic fluid flow remain hard to resolve from geodetic and seismologic data alone. Exhumed subduction zone rocks, such as those on Syros Island, Greece, provide key insights into the mechanical and hydrologic conditions within the SST source region. In this talk, I will present field-based and microstructural observations that reveal heterogeneity in viscosity, permeability, friction, and mineral fabrics, and discuss how these properties potentially influence deformation styles along subduction interfaces. These rock-based constraints help bridge the gap between geophysical observations and models, shedding light on the physical conditions that govern transitions between stable creep, slow slip, and seismic failure at depth.

In our Solar System, there are numerous mean-motion resonances for the minor bodies and satellites, but there are no mean-motion resonances between the planets. The first mean-motion resonance in an extrasolar planetary system – the 2:1 resonance between two Jupiter-mass planets around the star GJ 876 – was discovered in 2001. Since then, an increasing number of pairs of planets in or near mean-motion resonances and resonant chains of three or more planets have been detected. I will discuss the dynamics of these systems and the constraints that they provide on the formation and dynamical evolution of planets. Topics will include high-order mean-motion resonances in the HD 202206 and nu Ophiuchi systems and the formation of resonant chains near the inner edge of protoplanetary disks.

 Venus, Earth’s twin, is not only the closest planet to us in the solar system, it the closest to Earth in mass, density and size and yet it evolved very differently than the Earth. Venus has an atmosphere that has 90 times the surface pressure as the Earth with a surface temperature of 460 C. Venus does not have a system of plate tectonics like the Earth which is one of the key reasons that Earth is a habitable planet. So how did two planets with roughly the same physical parameters evolve so differently? The NASA Magellan mission to Venus in the Early 1990’s used radar to image the planet’s surface through the optically opaque atmosphere at ~150 m resolution and showed that Venus has a young surface that had been volcanically resurfaced with the last 500 million years. As much a Magellan informed us about Venus it also left many key questions about Venus’s planetary evolution unanswered. Two missions to Venus, VERITAS by NASA, and EnVision by ESA in partnership with NASA, will return to Venus in the 2030’s with the goal of answering how these planet’s evolved so differently. The answer to this question will help inform how many Earth and Venus like planets are there in other solar systems. Radars play a key role on each mission and this talk will describe their role in these missions to Venus and how in combination with the other instruments hope to resolve one of the key mysteries in planetary science.  

Our knowledge of the satellite population in the solar system has grown rapidly in the past 100 years.
In the early 1900s almost every known moon was a regular satellite — the large, primordial bodies that formed with their parent planets.
The Voyager flybys fundamentally changed that picture by revealing numerous small inner satellites of the giant planets, bodies likely tied
to ring-system evolution and ongoing collisional processing near the planet. Beginning around 2000, wide-field CCD surveys (e.g. CFHT, Subaru) opened a third population regime: most new discoveries were irregular or outer satellites — dynamically distinct, highly inclined, often retrograde
objects whose origins are not native to the planet system but are best explained as captured heliocentric planetesimals from the early solar system. At JPL, we develop and maintain ephemerides for all known satellites. The orbital models range from simple precessing ellipses to full dynamical models that include tides, relativistic terms, satellite libration, and high order gravity field expansions. These models draw on data sets spanning more than a century of astrometric measurements, from early visual observations to modern spacecraft tracking. Ultimately, satellite ephemerides are not just navigation products needed to point a telescope or fly a spacecraft – they are scientific observables that encode the history and dynamics of entire planetary systems. Each orbit tells a story about its origin, its interactions, and its ongoing evolution.
We will review the current state of satellite ephemerides across the solar system and highlight some interesting dynamical puzzles.

High-resolution spectroscopy is essential for resolving fine spectral features that reveal important physical processes in planetary, astrophysical, and heliophysical environments. However, traditional high-R instruments are large, complex, and incompatible with compact or distributed space platforms. We present a new generation of Spatial Heterodyne Spectroscopy (SHS) systems that overcome these limitations through a fully integrated, all-reflective, and monolithic design. Optimized for the FUV/EUV regime (10–200 nm), our SHS architecture delivers resolving powers of R ~20,000–100,000 in a compact form factor (<2U volume, <10 kg), making it ideal for CubeSats, SmallSats, and deep-space missions. We highlight critical system-level innovations, including thermal, optomechanical, and detector interfacing, as well as a validated performance model that includes sensor and electronics noise, optomechancial alignment tolerance, calibration and operation stability. These developments establish SHS as a scalable, high-fidelity spectroscopic solution for the next generation of space science missions.

Astrophotonics is the application of versatile photonic technologies to channel, manipulate, and disperse guided light from one or more telescopes to achieve scientific objectives in astronomy in an efficient and cost-effective way. The photonic platform of guided light in fibers and waveguides has opened the doors to next-generation instrumentation for both ground- and space-based telescopes. Utilizing the photonic advantage is a promising approach to massively miniaturize the next generation of spectrographs for ground- and space-based telescopes. I will discuss some of our recent results from our efforts to design and fabricate high-throughput on-chip astrophotonic spectrographs. These devices are ideally suited for enabling exciting science cases, such as measuring exoplanet masses and characterizing exoplanet atmospheres. I will also discuss specific approaches to make this technology science-ready and qualified for the next generation of space missions and potentially, planetary missions.

Surface observations of Saturn’s moon Titan revealed features characterized as dissected, elevated plateaus with high valley density known as labyrinth terrains. Of this terrain class, a subtype referred to as radial labyrinth is described as dome-shaped uplifts with radial channel patterns. Uplift of these radial labyrinths has been explained as cryomagmatic intrusions at the brittle-ductile transition zone. Here we propose an alternative hypothesis, that crustal heterogeneities in Titan’s upper clathrate crust introduce density differentials due to ethane-methane substitution, as ethane-rich liquids percolate into methane clathrate, inducing solid state flow and generating domal topography. This mechanism is analogous to salt tectonics on Earth and has similarly been evoked for dome formation on the dwarf planet Ceres. We show that the elevation and width of the observed radial labyrinths is consistent with domal uplift driven by a hydraulic head within the uppermost portion of Titan’s crust, given a plausible set of elastic parameters for clathrate hydrates. Additionally, the insulating effect of clathrate, combined with partial mixing with water-ice, allows for sufficiently low viscosity for geologic flow: uplift of the domes could have occurred early in Titan’s history, a billion years ago, or could have uplifted within the last 100 Myr during a recent phase of orbital excitation.

In this talk I will share our recently published results on the detection of potential biosignatures within the Neretva Vallis ancient riverbed on Mars, and then extend outward to our efforts to characterize and explore worlds of the outer solar system that harbor contemporary liquid water oceans beneath lithospheres of ice. At least six ice-covered moons of the outer solar system present compelling evidence for subsurface oceans, and thus provide highly compelling targets in our search for life beyond Earth. I will focus on Jupiter’s moon Europa, and detail experiments conducted in my lab that help us better understand Europa’s ocean chemistry and surface morphology. If time permits, I will also provide an overview of missions that will explore these worlds in the coming decades, and describe how exploration of Earth’s ocean and cryosphere is helping to guide our understanding of the potential habitability of these alien oceans.

Martian meteorites provide key information about the geological history of Mars. However, our collection is biased by geologically young samples that are not representative of Mars’ exposed surface, which is dominated by ancient rocks. This generates gaps in our knowledge of Mars’ early evolution. Recently, we discovered that a Martian meteorite, Teghaza 001, is a gabbroic diorite with a crystallization age > 4.1 Ga. In this presentation, I will describe this unique sample, how it compares to other Martian meteorites and igneous rocks studied by rovers, what results imply to our understanding of early Mars differentiation.

In our Solar System, there are numerous mean-motion resonances for the minor bodies and satellites, but there are no mean-motion resonances between the planets. The first mean-motion resonance in an extrasolar planetary system – the 2:1 resonance between two Jupiter-mass planets around the star GJ 876 – was discovered in 2001. Since then, an increasing number of pairs of planets in or near mean-motion resonances and resonant chains of three or more planets have been detected. I will discuss the dynamics of these systems and the constraints that they provide on the formation and dynamical evolution of planets. Topics will include high-order mean-motion resonances in the HD 202206 and nu Ophiuchi systems and the formation of resonant chains near the inner edge of protoplanetary disks.

Zircon continues to grow in importance as a probe of the crust, both its current architecture and the parts of it that have been lost to erosion over deep time. A wide array of applications in the earth sciences, ranging from tectonic reconstructions of modern-day crustal terranes to investigation of Earth’s earliest crust in the Hadean Eon, benefit from being able to fully exploit the information trapped in zircon about its source rocks and the environments in which they formed. One less-explored avenue for reconstructing zircon source rocks is the mineral inclusions trapped in them, whose interpretation is somewhat complicated compared to direct age and isotopic results from the host zircons themselves. This talk presents three projects showing different applications of inclusions in detrital zircon that were derived from igneous rocks. First, the proportion of apatite in a zircon inclusion assemblage can help to predict how felsic the source magma was, and avoids some of the biases that impede this when the prediction is made using the major minerals quartz and feldspar. Second, the Fe-Ti oxides trapped as inclusions in zircon reflect the redox state of the magma from which the zircon grew, and can help to reconstruct the source magma when other indicators such as trace elements in the host zircon are more ambiguous or overprinted. Third, the proportion of inclusion phases made up of highly incompatible trace elements helps to predict whether a detrital population had significant provenance from highly felsic leucogranites, which are significant both in the context of crustal maturation and mineral exploration. Future applications involving inclusions in zircon will be able to exploit the trace element and isotopic information that is available on increasingly smaller spatial scales due to tools like the ion microprobe.

Xenon isotopes trace Earth’s deep volatile history, but present-day mantle Xe observations display a paradox: atmospheric-like isotopic ratios require substantial regassing, while the low concentration requires limited regassing. Previous models resolved this by invoking early limited regassing, but this is hard to reconcile with evidence for early plate tectonics, higher Xe concentrations in the ancient atmosphere, and incomplete noble gas removal from subducting slabs. We use a parameterized thermal evolution and material recycling framework to explore time-dependent degassing and regassing histories, including Xe loss through continental crust extraction, mid-ocean ridge and plume melting, and Xe recycle via subduction. We show that strong early Xe loss driven by rapid early continental crust generation reduces the bulk mantle concentration enough to make later regassing effective at reproducing the isotopic ratios. Fissiogenic Xe constraints and the required intense early degassing together favor lower initial mantle uranium concentration, pointing to starting compositions with at least an enstatite-chondrite component rather than purely CI-chondritic material. Analytical solutions with simplified approximation and machine learning analysis confirm that these requirements are linked: low uranium and large early crustal extraction are coupled, and early degassing controls the timescale over which the system transitions to moderate degassing or regassing. Our results show that a major early degassing episode with prolonged moderate regassing can explain both the isotopic ratios and concentrations, offering an alternative to limited regassing scenarios and new constraints on Earth’s starting materials and early history.

Rare earth element abundances have been used to gain key insights into the origin and evolution of silicate melts on the Earth and other planetary bodies. It is now possible to measure natural, non-radiogenic variations in the isotopic compositions of many of these elements, but it’s not clear what controls them. This project aims to estimate equilibrium isotope fractionation in rare earth elements theoretically, which is a challenging problem because both mass dependent and mass independent effects are important. The two redox-sensitive REEs, cerium and europium, are contrasting examples. In the case of Ce(IV) vs. Ce(III), the relative importance of mass-dependent vs. mass-independent fractionation – and even the direction of fractionation – is predicted to be strongly dependent on the isotope pair measured. In the case of europium, mass-independent fractionation is dominant. Eu(II)-bearing species such as plagioclase are predicted to have higher 153Eu/151Eu than Eu(III)-bearing species by ~0.2-0.3‰ at magmatic temperatures, which is in qualitative agreement with recent measurements.

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Mentor
Dr. Carolina Lithgow-Bertelloni

Mentors
Dr. Hao Cao, Yingjuan Ma

Mentor
Dr. Lingsen Meng

Mentor
Dr. Lars Stixrude

Mentor
Dr. Abby Kavner

Mentor:
Dr. Mackenzie Day

Location:
Slichter 3853

Mentor:
Dr. Lars Stixrude

Location:
Slichter 3853

Asteroids are the leftover building blocks that accreted to form the terrestrial planets. As such, they tell us about the initial conditions that existed in our solar nebula some 4.6 Gyrs ago. In particular, their density and internal structure result directly from their place and time of formation. Large asteroids with satellites represent the best opportunity to probe these fundamental parameters, and high-angular resolution imaging techniques provide the most effective tool to study these objects without visitation. I will discuss how recent developments in instrumentation and image processing techniques have allowed us to improve our understanding of asteroid shapes, internal structure, and satellite dynamics, as well as what this improved understanding can reveal at a population level.