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Planetary Science SEMINARS - Spring 2022
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Campus and bay-area speakers will present in person. Remote speakers will present over Zoom.
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Wednesdays 1:10-2:00 PM
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For a Zoom link to the meeting please contact: militzer @ berkeley . edu
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DateSpeakerAffiliationTitleAbstractHost
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19-JanNatasha Batalha (virtual)NASA AmesThe Open Access Era of Exoplanet Characterization at the Onset of Next-Generation Telescopes One of NASA's primary goals is to observationally characterize exoplanet atmospheres, understand the chemical and physical processes of exoplanets and improve the understanding of the origins of exoplanetary systems. Throughout the next decade and beyond, JWST, Roman, future mission concepts, and ground based telescopes will work towards achieving these goals by interpreting a diverse set of exoplanet atmosphere observations, ranging from hot gas giants to small temperate rocky worlds. Our understanding and interpretation of this full gamut of spectroscopy data will hinge on our ability to accurately link observations to theoretical models. Therefore, it is imperative that our theoretical models are equipped to tackle these problems. Leading up to this new era in exoplanetary space science, one of our goals has been to ensure that the community is equipped with robust, user-friendly, open-source, theoretical models needed to both plan and execute ground-breaking science. Open access tools increase the accessibility of our science, the diversity of ideas, and naturally foster betters collaborations. I will first discuss the current landscape of theoretical exoplanet model development. Then, I will discuss our recent developments in cloud, opacity, and spectroscopy models that are working together to enable effective interpretation of exoplanet spectroscopy.Diogo Lourenço
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26-JanBurkhard Militzer (virtual)UC BerkeleyThe Interior Structure of Jupiter and Saturn This talk will discuss the recent gravity measurements of Saturn and Jupiter by the Cassini and Juno spacecrafts. During the Grand Finale phase, the Cassini spacecraft traveled inside Saturn’s rings and measured the planet’s gravitational field with high precision. The magnitudes of gravity coefficients J6, J8, and J10 were unexpectedly large and could not be explained with traditional interior models that assumed uniform rotation. So we introduced differential rotation on cylinders and showed that all even coefficients J2 through J10 can be matched. Since its arrival at Jupiter in 2016, the Juno spacecraft has measured the planet’s gravity field with every flyby. The interpretation of these measurements has again been challenging but in this case because the magnitudes of the gravity coefficients J4 and J6 were smaller than predicted by traditional interiors models that included a dense inner core composed of rock and ice. Here we instead present models with dilute cores and deep winds.Diogo Lourenço
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2-FebDavid Shuster (virtual)UC BerkeleyPerseverance on Mars: Selecting samples of Mars to return to Earth. I’ll provide a general overview of the Mars 2020 Perseverance rover mission from a sampling perspective. I’ll discuss the motivating science questions, the geologic setting of the Jezero crater landing site, the overall sample return objectives, and the sampling strategies, timeline and challenges. I will discuss the samples collected and the geologic setting and history that we have, thus far, worked out during the first 11 months of the mission.Anton Ermakov
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9-FebIshan Mishra (virtual)Cornell UniversityProviding new constraints on Europa's surface compositionComposition of Europa's surface remains our best window into the composition of its subsurface ocean, and spectroscopy is our primary tool for characterizing its surface's composition. Of special interest are trace species like organics and oxides, whose presence and abundance distributions can provide valuable insights into the potential habitability of the subsurface ocean. I will present a data analysis framework for reflectance data, based in Bayesian statistics, that specializes in picking out trace signals in spectroscopic data. This Bayesian framework can quantify confidence in the presence of a given species, constrain its parameters like abundance and average grain size with confidence intervals, and explore solution degeneracies. I will show examples of its application to Europan data from Juno and Galileo missions in my recently published works. I will also talk about my current project of using this framework to assess the feasibility of detection and characterization of organics on Europa with current and upcoming instruments. Burkhard Militzer
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16-FebHayley Beltz (virtual)University of Michigan...High resolution spectroscopy (R~100,000) has opened the door to planetary atmospheric characterization at an unprecedented level. With this increase in resolution, more sophisticated models, specifically those in 3D, are necessary to utilize these spectra to their fullest potential. In this talk, I discuss my work on 3D atmospheric modeling of hot and ultrahot Jupiters and how these planets are especially amenable to 3D modeling. Additionally, I will discuss the impact of our locally calculated magnetic drag implemented in our 3D model on the atmospheric structure and emission spectra of ultrahot Jupiters.Marta Bryan
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23-FebPascale Garaud (virtual)UC Santa CruzDouble-diffusive convection in the interior of giant planetsIn this talk I will describe what is known of convection in the presence of very strong stabilizing compositional gradients, which is relevant in several regions of the interiors of giant planets, in particular in the vicinity of the core. Convection in these regions can become double-diffusive, relying on the unequal diffusivities of temperature and composition to proceed. Several forms of double-diffusive convection exist, including a wave-like form, and a layered form, with vastly different properties. I will present theoretical results on thermal and compositional transport by both forms of double-diffusive convection, with and without magnetic fields, and make tentative remarks on their relevance for giant planets. Diogo Lourenço
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2-MarShannon Curry (virtual)Berkeley/SSLMars: Past, Present and Future with the MAVEN missionThe Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been making observations of the Martian atmosphere since its arrival in 2014 to characterize atmospheric evolution at Mars. Currently, MAVEN is the best observer of atmospheric escape anywhere in the solar system, including Earth, making Mars a natural laboratory for understanding rocky planet atmospheres. MAVEN is not only able to take measurements of the upper atmosphere, but it can also observe inputs from the Sun (EUV, solar wind and energetic particles) as well the crustal magnetic fields embedded in the southern hemisphere of Mars. In effect, MAVEN is able to observe the drivers from above and below to determine how much of the Martian atmosphere has been lost over time. Atmospheric escape is particularly important for understanding the history of water on Mars; in order for water to have existed in liquid form on the surface, the atmospheric pressure had to have been substantially higher than it is today. As this thicker atmosphere eroded over time, the water in liquid form was sequestered in the crust and stored as subsurface ice. Thus, by measuring the current rate of atmospheric escape to space and extrapolating back in time, we can better understand Mars’ climate and reservoirs of water. During this talk, we will discuss a variety of new discoveries at Mars over the last 3 Martian years (nearly seven Earth years), from November 2014 to present, and how those have enabled the team to quantify the loss of atmospheric gases to space over Martian history. In addition to understanding Mars’ past and present atmosphere, we will discuss the future goals, observations and collaborations for MAVEN.Anton Ermakov
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9-MarCANCELLEDSarah Arveson
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16-MarJean-Luc Margot (virtual)UCLASpin state and moment of inertia of VenusEarth-based radar observations in 2006–2020 enabled the first measurement of the spin precession rate and moment of inertia of Venus. The observations also showed that the spin period of the solid planet changes by tens of minutes. The length-of-day variations are due to variations in atmospheric angular momentum transferred to the solid planet. Some of the variations appear to follow the diurnal cycle.Anton Ermakov
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23-MarSpring break - no seminar............
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30-MarJanosz Dewberry (in-person)CITA/CaltechImpacts of rapid rotation on the oscillations and tides of gas giant
planets
Many planets, stars, and compact objects rotate rapidly, to the point
where they can no longer be reasonably approximated as spherically
symmetric. Such rapid rotation modifies seismic oscillations, as well as
the response of the planet or star to tidal forcing by a satellite or
binary companion. Our understanding of the details of this modification
is still limited, but fortunately our own solar system hosts two prime
examples of (moderately) rapidly rotating, oscillating and tidally
interacting gaseous bodies: Jupiter and Saturn provide excellent
opportunities to refine theoretical and numerical methods, while at the
same time learning more about planetary interiors. In this talk, I will
discuss recent investigations into the effects of rapid and differential
rotation on internal oscillations inferred from their influence on
Saturn's rings. I will additionally describe work focused on the tidal
response of rapid rotators that are significantly centrifugally
distorted.
Anton Ermakov
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6-AprCharitra Jain (virtual)GFZ PotsdamEarly Earth evolution and continent formationSubduction-driven plate tectonics and continents are considered to play an important role in the atmospheric evolution of Earth, thereby helping stabilise its climate on long-term timescales and contributing towards planetary habitability. In contrast to the present-day, Earth's mantle during the Archean was considerably hotter and rheologically different. For the early Earth, following the magma ocean solidification stage, a variety of tectonic regimes, such as heat-pipe tectonics, plutonic-squishy lid, stagnant lid have been proposed albeit without any consensus. And when it comes to narrowing down the onset of modern-style plate tectonics, opinions vary widely with a multitude of studies proposing its inception anytime between the Hadean Eon (4.5-4.0 Ga) and the Neoproterozoic Era (1.0-0.54Ga). Was it the emergence of continents that led to plate tectonics or vice versa? Furthermore, the rheological changes required to make the (supposedly gradual) transition to modern style plate tectonics on Earth remain hotly debated. In this talk, I will present global convection models employing different rheologies that make continental crust and their underlying cratonic roots in a self-consistent manner. Based on these results, I will comment on what tectonic regimes are suitable for their formation and preservation.Diogo Lourenço
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13-AprMaaike van Kooten (in-person)UCSCTowards extreme adaptive optics for giant segmented telescopes: the impact of atmospheric turbulence from multi-decadal to millisecond timescalesWhile adaptive optics (AO) systems have now been deployed on nearly every 10-meter-class observatory, the state-of-the-art in AO technology development does not yet meet the needs of the next generation of giant, segmented telescopes, especially in the context of direct imaging and characterization of exoplanets. In this talk, I address the impact of atmospheric turbulence on the design of extreme AO systems, focusing on two very different timescales, investigating: 1. over the last 40 years, what are the effects of climate change on optical turbulence and, therefore, the design of our AO systems, and 2. can we predict turbulence on milli-second timescales to improve the performance of our AO system? The talk will be divided into two parts, where I first introduce the climatology of Mauna Kea using summit data and numerical weather model output (i.e., re-analysis datasets such as ERA5). The second half of the talk will focus on technology development specifically for high contrast imaging (HCI). As the HCI community prepares for giant segmented telescopes and pushes toward contrasts enabling the direct imaging and characterization of radial-velocity detected exoplanets, the performance of the AO system needs to be improved. I will present on-sky results from testing advanced AO methods on W.M. Keck Observatory, showing that by predicting the evolution of the turbulence on timescales of the AO system we can improve achievable contrast on NIRC2.Marta Bryan
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20-AprMor Rozner (in-person)Israel Institute of TechnologyInflated Eccentric Migration of Evolving Gas-GiantsHot and warm Jupiters (HJs and WJs correspondingly) are gas-giants orbiting their host stars at very short orbital periods (PHJ<10 days; 10<PWJ<200 days). HJs and a significant fraction of WJs are thought to have migrated from an initially farther-out birth locations. While such migration processes have been extensively studied, the thermal evolution of gas-giants and its coupling to the migration processes are usually overlooked. In particular, gas-giants end their core-accretion phase with large radii and then contract slowly to their final radii. Moreover, intensive heating can slow the contraction at various evolutionary stages. The initial inflated large radii lead to faster tidal migration due to the strong dependence of tides on the radius. We explore this accelerated migration channel via semi-analytical and numerical methods and demonstrate our model for specific examples as well as a detailed population synthesis study based on our semi-analytical model. Our results provide a general picture of the properties of the formed HJs&WJs via inflated migration, and the dependence on the initial parameters/distributions. We show that tidal migration of gas-giants could occur far more rapidly than previously thought and lead to accelerated destruction and formation of HJs and enhanced formation rate of WJs. Accounting for the coupled thermal-dynamical evolution is therefore critical to the understanding of HJs/WJs formation, evolution and final properties of the population and plays a key role in their migration process.Anton Ermakov
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27-AprKaren Meech (virtual)University of Hawaii, Institute for AstronomyFormation of Habitable Worlds: Origin of Earth’s WaterSmall primitive bodies can provide information about the solar system’s formative processes, including the contribution of pre-solar and interstellar sources. Interstellar objects are thought to be planetesimal remnants that have been ejected out of their own solar system, and they can provide insight into the process of building exoplanetary systems. The most primitive Solar System objects are found beyond the asteroid belt. They have largely been undisturbed since their formation. Thus, their compositions provide a fossilized record of the chemical make-up of our planetary system during its origin. No one knows if our solar system, with a planet possessing the necessary ingredients for life within our Sun’s habitable zone, is a cosmic rarity. Nor do we know whether the gas giants in our solar system played a role in helping to deliver the essential materials for life to the habitable zone. The answers to these questions are contained within ices found in small bodies that are mostly unchanged since the formation the solar system. The most likely source of Earth’s water may have been in the outer solar system. Evidence of what arrived at Earth is hard to determine from Earth’s materials because of all the geological the processing that has occurred. Comets were long thought to be the most likely “delivery service” of Earth’s water. But new models and new data, including the Rosetta mission’s survey of comet 67P, have cast doubt. A new class of objects, the Manx comets, may provide clues to allow us to trace the history of the movement of materials in the inner solar system. However, to learn where Earth’s water came from, we also have to match the chemical fingerprints various unchanged solar system materials to where we think they formed. The question is, are there any small unheated bodies today that preserve this ancient record? Whatever was delivered to Earth was also trapped in the asteroid belt where some of those materials exist today. Main belt comets are part of a population of icy asteroids that reside in the outer asteroid belt, that like comets, form tails. They may have formed where they are today, or might have been place there by the influence of the gas giant planets as they grew. This talk will explore what we know about the origin of Earth’s water, and the new ideas for space missions that could help solve this question.Anton Ermakov
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4-MayBirger Schmitz (virtual)Lund UniversityFossil meteorites, extraterrestrial spinels and the astronomical perspective on Earth's geological record – What can 50 tons of rock and 100,000 litres of hydrochloric acid tell us?We use unique fossil meteorites, 1-20 cm large, from a quarry in mid-Ordovician limestone and relict, sand-sized spinel grains from decomposed micrometeorites in ancient sediments for the very first reconstructions of the variations in the types of meteorites that fell on Earth in deep time. Meteorite falls are rare and meteorites weather and decay rapidly on the sea floor making it a challenge to reconstruct ancient fluxes. The refractory spinels are recovered by dissolving tons of sediments in acids. The standard view of meteorite delivery to Earth is that of the cascading model where large asteroid break-ups generate new fragment populations that feed the inner solar system with material for extended time periods. Our investigated time windows, stretching from the Cambrian to the present, do not support this model. In fact, of 70 major family-forming break-ups the past ∼500 Myr, only one appears to have given rise to a strongly enhanced flux of asteroids and meteorites to Earth. We argue that meteorites and small asteroids delivered to Earth in deep time are not primarily linked to the sequence of asteroid family-forming events. Our results indicate that most of Earth's impact craters were formed by projectiles of the ordinary chondritic type, i.e. the meteorite type that represent ca. 80% of the meteorite falls in today's world. With at least 160 different types of asteroids in the asteroid belt, it is a major conundrum why one type, the ordinary chondrites, so strongly has dominated the meteorite flux to Earth for at least the past 500 Myr.Diogo Lourenço
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11-MayShreyas Vissapragada (virtual)Caltech......Marta Bryan
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