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Planetary Science SEMINARS - Fall 2020
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Online over Zoom
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Wednesdays 1:10-2:00 PM
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For a link to the meeting please contact: swahl @ berkeley . edu
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DateSpeakerAffiliationTitleAbstractHost
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26-AugFirst day of instruction
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2-SepAnton ErmakovBerkeleyCeres' interior from Dawn’s second extended missionThe analysis of Ceres’ gravity and topography data from the Dawn’s Primary Mission (PM) showed that Ceres is partially differentiated with a mechanically strong crust overlaying a weak, fluid-bearing upper mantle. Dawn’s Second Extended Mission (XM2) yields a spatially limited high-resolution gravity field. This allows to locally sample shallower subsurface structures, compared to the PM data, and reveals a complex crustal structure. The XM2 gravity data implies a radial density gradient within Ceres’ crust that is consistent with decreasing porosity with depth and/or increasing content of dense phases, such as rock and salts. That gradient brings a critical new constraint on the crust freezing history, suggesting that the salts and silicates concentrated in the liquid phase while the crust was growing. Gravity data and thermal modeling imply an extensive deep brine reservoir beneath Occator crater, which could have been mobilized by the impact heating and deep fracturing associated with the Occator impact, leading to long-lived extrusion of brines and formation of the evaporite deposits. Pre-existing fractures may also provide pathways for deep brines to migrate through the crust, extending the regions affected by impacts and creating compositional heterogeneity. The long-lived hydrological system created by the impacts could potentially also occur for large impacts in icy moons, with implications for the creation of transient habitable niches over time.Burkhard Militzer
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9-SepMunazza AlamHarvardCharacterizing Giant Planet Atmospheres with HubbleWith over 3,000 exoplanet discoveries to date, we have caught a glimpse of the broad diversity of exoplanets that span a range of masses, compositions, and orbital configurations. The next chapter in exoplanet exploration will focus on understanding the atmospheres of Jupiters to super-Earths, and we are now poised to begin large-scale atmospheric studies of exoplanets with current instruments on the Hubble Space Telescope (HST) via transmission spectroscopy. The HST Panchromatic Comparative Exoplanetology Treasury (PanCET) Program will assemble the first statistically significant sample of exoplanet atmospheric observations in the ultraviolet, optical, and infrared. As part of PanCET, we present precise optical to near-infrared (~0.3-5 microns) transmission spectra for three hot Jupiters using combined HST and Spitzer transit observations. We compare the transmission spectra to a grid of 1D radiative-convective forward models and retrieve the planetary atmospheric properties. These broadband observations will constrain the atmospheric structure and chemical composition of the most favorable targets for atmospheric follow-up with JWST. Sean Wahl
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16-SepTim LichtenbergU. OxfordEarliest compositional bifurcation of planetary building blocksIn this talk I will introduce a novel scenario for the origin of the Solar System that reframes the early compositional chronology of the terrestrial planets. Recent astronomical and geochemical evidence point to early spatial and temporal fragmentation of the planet formation process, whose physical origins remain disputed. Using a coupled numerical model, I will investigate the influence of the build-up of the solar protoplanetary disk on the timing and internal evolution of forming protoplanets. The results of these simulations demonstrate that the orbital drift of the water iceline can generate two temporally and spatially distinct bursts of planetesimal formation, which sample different source regions of interstellar materials and experience limited intermixture of primordial nucleosynthetic signatures. Driven by internal radiogenic heating, the formed planetary reservoirs in the inner and outer disk compositionally evolve in two modes and recover accretion chronology, temporal clustering of iron core formation and aqueous alteration in the meteoritic record, and mass divergence of inner and outer Solar System. The presented scenario suggests that the earliest interplay between disk physics and geophysical evolution of accreting planetesimals initiated the present-day observed chemical fractionation and isotopic dichotomy between the inner and outer Solar System planet populations.Diogo Lourenço
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23-SepDiana PowellUCSCProtoplanetary Disks and Clouds in Substellar Atmospheres: Insights from MicrophysicsIn this talk, I will provide evidence that protoplanetary disks are more than an order of magnitude more massive than previously appreciated, that the detailed properties of clouds shape observations of substellar atmospheres, and that the physics of modeling clouds gives a new understanding of the solid content in protoplanetary disks. Clouds on extrasolar worlds are seemingly abundant and interfere with observations; however, little is known about their properties. In our modeling, we predict cloud properties from first principles and investigate how the interesting observational properties of hot Jupiters and brown dwarfs can be explained by clouds. Next, I will report on a new set of models that reconcile theory with observations of protoplanetary disks and create a new set of initial conditions for planet formation models. The total mass available in protoplanetary disks is a critical initial condition for understanding planet formation, however, the surface densities of protoplanetary disks still remain largely unconstrained due to uncertainties in the dust-to-gas ratio and CO abundance. I make use of recent resolved multiwavelength observations of disks in the millimeter to constrain the aerodynamic properties of dust grains to infer the total disk mass without an assumed dust opacity or tracer-to-H2 ratio. Finally, I will present new work that combines the microphysics of cloud formation in planetary atmospheres and our new models of protoplanetary disks to show that the observed depletion of CO in well-studied disks is consistent with freeze-out processes and that the variable CO depletion observed in disks can be explained by the processes of freeze-out and particle drift.Marta Bryan
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30-SepSamantha TrumboCaltechThe Surface of Europa: A Window to the Ocean Below Jupiter’s moon Europa is a prime target for exploring habitability in the Solar System. Beneath a comparatively thin ice shell, Europa harbors a global, salty, liquid-water ocean that is likely in contact with a rocky seafloor. Its geologically young, fractured surface suggests a history of exchange between the ocean and surface environments, such that the surface composition may reflect that of the internal ocean to some degree. However, the interpretation of surface constituents as oceanic signatures is complicated by the fact that Europa’s surface is continuously radiolytically processed by electron and ion bombardment, due to its location within Jupiter’s magnetosphere. I will present a suite of multi-wavelength observations of Europa from the Hubble, Keck, and ALMA observatories with the goal of disentangling these effects from endogenic delivery. These observations have begun to change our understanding of Europa’s surface chemistry, internal composition, and the relationship between the two, providing a renewed glimpse into the ocean below.Imke de Pater
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7-OctMorgan CableJPLExploring Ocean WorldsOur solar system is host to multiple ocean worlds - planets and moons that contain oceans of liquid, usually water, either on their surfaces or underneath icy crusts. These worlds are prime targets of exploration due to NASA’s quest to ‘follow the water’ and may contain all three ingredients for life as we know it - water, chemistry, and energy. Could life exist in the oceans of Enceladus or Europa? Could even stranger life have emerged in the liquid methane lakes of Titan? We will cover our current state of knowledge of these ocean worlds, and discuss some current missions and future mission concepts to explore their plumes, surfaces, and ocean depths.William Newman (UCLA)
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14-OctSara WalkerASUInferring the “Laws of Life” at a Planetary ScaleIn 1943 Erwin Schrodinger famously delivered a set of lectures at the Dublin Institute for Advanced Studies aiming to tackle the question “What is Life?” from the first-principles approach of a theoretical physicist. Over 70 years later, we’ve still made little headway in coming up with a general theory for what life is. While many definitions for life do exist, these are primarily descriptive, not predictive, and they have so far proved insufficient to explain the origins of life from non-living matter, or to provide rigorous constraints on what properties are universal to all life, even that on other worlds. Yet, as NASA and other space agencies are setting sights on life detection as a goal of upcoming robotic missions and space observatories, more rigorous understanding of the universal properties of living matter are becoming increasingly vital to uncover. In this talk I discuss new approaches to understanding what universal principles might underlie living matter and how to generate it, based on studying biochemical networks on Earth from the scale of individual organisms to the planetary scale. William Newman (UCLA)
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21-OctEugene ChiangUC BerkeleyThe Endgame of Planet FormationSuper-Earths/Sub-Neptunes are planets ~1-4 Earth radii and ~1-20 Earth masses, composed of solids and gas in proportions of 100:1 by mass. We describe how super-Earths/sub-Neptunes form: the assembly of their rocky cores, the accretion of their atmospheres, and the distribution of their orbits inside and outside of mean-motion resonances.William Newman (UCLA) / Anton Ermakov (UC Berkeley)
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28-OctDPS and GSA meetings - no seminar
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4-NovMatthew SieglerPlanetary Heat Flow: InSight on Mars and Insights into the Moon Dr. Matthew Siegler will present an overview of new work in measuring and modeling planetary geothermal heat flow on the Moon and Mars. He will give us an update on insitu measurements from the Mars InSight lander and plans for a Lunar Geophysical Network as well as an overview of exciting new remote measurements from LRO, Chang'E-2 and the VLA that show promise of constraining subsurface temperatures of solid planets from orbit and Earth-based radio observations.

Matt Siegler is a research scientist at Planetary Science Institute and based in Dallas, TX. He specializes in all things thermal, including thermal modeling, infrared and microwave remote sensing, volatile stability, geothermal heat, and laboratory thermal measurements. He is a Co-I on LRO, InSight, OSIRIS-REx, 2 lunar CLPS instruments, and the upcoming Viper lunar rover. He will be talking about the struggles of measuring geothermal heat flow on Mars and how microwave instruments may aid in future missions. He is father to Jack and June and in the process of making them an awesome treehouse.
https://matthewasiegler.wixsite.com/mattsiegler 		William Newman (UCLA) / Diogo Lourenço (UC Berkeley)
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11-NovAcademic Holiday
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18-NovTim GoudgeU AustinCharacterizing the Incision of Ancient Lake Outlet Canyons on MarsSome of the best geologic evidence for liquid water on the ancient surface of Mars (>3.5 Ga) is its record of paleolake basins. Of the >250 early Mars paleolake basins identified from orbit, the majority (>85%) have an outlet canyon that drained the lake. The formation of such outlet canyons requires a transition from an originally enclosed topographic basin to an open lake hydrologically connected to the exterior terrain via incision of an outlet. In this talk I will present analyses of the topography and geometry of martian paleolake outlet canyons to test whether they were incised by catastrophic lake overflow flooding or long-term outflow that balanced inflow to the lake. Included in this analysis is a comparison of our results to observations of breached lake basins on Earth to test whether observed geometric scaling relationships are consistent across the two planets.William Newman (UCLA)
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25-NovLaura KerberJPLMoon Diver
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2-DecBrittany MilesUCSCTBDTBDMarta Bryan
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9-DecReading Week
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16-DecFinal Exams
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