Colloquium

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.