Planetary Science Seminar - winter-2022


Mimas, that’s no (ocean) moon! Or is it?

Jan. 6, 2022
noon - 12:50 p.m.
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Presented By:

  • Alyssa Rhoden - SouthWest Research Institute, Boulder
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Mimas is the innermost “regular” moon of Saturn. It’s small and heavily cratered, suggesting that Mimas lacked sufficient internal heating to drive geologic activity. However, Cassini measurements of its libration require that Mimas either has a non-hydrostatic core or a subsurface ocean, and the phase of the libration is more consistent with an ocean. Either interpretation implies that Mimas is differentiated, challenging traditional models of its formation, evolution, and age. Determining whether Mimas has an ocean today will help constrain the possible histories of Mimas and its neighboring moons. Also, if Mimas were shown to have an ocean, it would represent a new class of small, “stealth” ocean worlds, whose surfaces do not betray the ocean’s existence. I will describe the current state of knowledge about this curious moon, whether estimates of tidal heating support the presence of an ocean despite Mimas’ high eccentricity, and how we might be able to use spacecraft measurements to determine whether Mimas is, indeed, an ocean moon today.  https://www.boulder.swri.edu/about/staff/doss/Rhoden.Alyssa.html


Unsolved Mysteries of Ancient Meteoritic Material

Jan. 13, 2022
noon - 12:50 p.m.
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Presented By:

  • Emile Dunham - EPSS, UCLA
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Calcium-Aluminum-rich Inclusions (CAIs) found in meteorites are the first solids formed in the Solar System so they hold keys detailing how the Solar System was formed. There are a number of unsolved CAI mysteries like how they were transported from the inner Solar System and why they have distinct distributions in different meteorites. I will give an overview of CAIs and why we care about them, with the goal of highlighting open questions. https://www.hsfoundation.org/fellow/emilie-dunham-ph-d-candidate/


Hunting Planet Formation in the Act: Theory, Observation, and Machine Learning

Jan. 20, 2022
noon - 12:50 p.m.
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Presented By:

  • Jaehan Bae - University of Florida
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Over the last few decades, astronomers discovered more than 4,000 exoplanets orbiting around stars other than the Sun. The discovery suggests that planet formation is ubiquitous in our galaxy. However, exoplanets exhibit great diversity, raising challenging questions about planet formation processes. One of the best ways to learn about planet formation processes is to observe planets while they are forming. The task of observing young, forming planets has long been very challenging, but it has finally become possible with increasingly powerful observing facilities and techniques. In this talk, I will review recent high-resolution observations of protoplanetary disks – the birthplaces of planets – and introduce how state-of-the-art observations, along with theories, numerical simulations, and machine learning, can help us better understand planet formation processes. Finally, I will discuss what we can learn from protoplanetary disk studies about the planet formation in the solar nebula.   http://jaehanbae.com/


Atmospheric evolution of Venus and exo-Venus analogs

Jan. 27, 2022
noon - 12:50 p.m.
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Presented By:

  • Joshua Krissansen-Totton - Dept Astronomy & Astrophysics, UCSC
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Interpreting upcoming observations of highly irradiated terrestrial exoplanets may be contingent on understanding Venus's atmospheric evolution. Here, I present a coupled atmosphere-interior evolution model for hot terrestrial planets to constrain Venus's past climate and investigate the fate of oxygen leftover from hydrogen escape. Initial results suggest both habitable and never-habitable histories can be broadly reconciled with geochemical constraints and that efficient oxygen sinks must be invoked to explain the current atmosphere.  http://www.krisstott.com/


Small body science in the inner-most reaches of the solar system

Feb. 3, 2022
noon - 12:50 p.m.
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Presented By:

  • Matthew Knight - Dept. Physics, US Naval Academy
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Over the last 25 years, SOHO and other solar observatories have revealed that the near-Sun region is rich with previously unknown comets and asteroids. Most of these objects are destroyed during their passage through the harsh environment, yet some persist on short-period orbits. I will give an overview of the populations and highlight some of the results that yield insight into the processes at work in our solar system. https://www.usna.edu/Users/physics/knight/


Melting of H2O on Recent Mars at High-Obliquity

Feb. 10, 2022
noon - 12:50 p.m.
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Presented By:

  • Jay Dickson - Geological & Planetary Sciences, Caltech
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Mars is currently extremely cold and dry and generally incapable of producing meltwater from abundant near-surface H2O-ice deposits. This talk will present Global Climate Model (GCM) simulations of Mars at 35° obliquity, 10° higher than present, that show that regions of Mars that surpassed the triple point of H2O directly match regions that host morphological evidence for geologically recent meltwater production. Mars last experienced this high-obliquity configuration within the last million years, considerably more recent than the more generally accepted era of a wet and potentially habitable early Mars billions of years ago. http://web.gps.caltech.edu/~jdickson/site/jld-index.html


Investigating present-day surface activity on Mars with past, operating, and potential future spacecraft

Feb. 17, 2022
noon - 12:50 p.m.
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Presented By:

  • Serina Diniega - Jet Propulsion Laboratory
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Surface-atmosphere interactions are key active processes on rocky planetary bodies, and studying how they operate on Mars helps us interpret the expression of such processes outside of Earth conditions. In particular, studies of how volatiles and sediment (sand/dust) move and actively shape the martian surface can yield key insight for analogous features on outer solar system bodies. This talk will give an overview of observed martian surface processes, and then look toward potential future investigations that would significantly advance our understanding of how martian, and other extraterrestrial, surfaces evolve.   https://science.jpl.nasa.gov/people/Diniega/


The consequences of silicate vapor in determining the structure, radii, and evolution of sub-Neptunes

Feb. 24, 2022
noon - 12:50 p.m.
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Presented By:

  • William Misener - EPSS, UCLA
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Substantial silicate vapor is expected to be in chemical equilibrium at the base of sub-Neptune atmospheres, but previous atmospheric structure models have neglected this chemical coupling. We show that the mean molecular weight gradient induced by this silicate vapor can inhibit convection at the base of a hydrogen-rich sub-Neptune atmosphere. We demonstrate the major effects of silicate vapor on the inferred atmospheric masses and thermal evolution of this common class of exoplanet. https://epss.ucla.edu/people/students/928/


Interstellar Interlopers and Centaurs

March 3, 2022
noon - 12:50 p.m.
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Presented By:

  • Darryl Seligman - Dept. Geophysical Sciences, University of Chicago
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In the first part of this talk, I will discuss ideas for the nature and origin of the first detected interstellar interloper, 1I/'Oumuamua. In the second part I will discuss the dynamics of escaped Kuiper belt objects ("Centaurs’") and their transition to the terrestrial planet region. https://www.darrylseligman.com/