Planetary Science SEMINARS - Fall 2022
Campus and bay-area speakers will present in person. Remote speakers will present over Zoom.
Wednesdays 1:10-2:00 PM. In-person talks will be in 131 Campbell Hall. Typically we will provide a simple lunch from 12:45-1:05
For a Zoom link to the meeting please contact: militzer @ berkeley . edu
Recordings from past presentations can be found here: https://drive.google.com/drive/folders/1it7b0Z_QRXCAktz-szIShkR1-2L0oO72?usp=sharing
|24-Aug||Chris Moeckel||In person||UCB||Ammonia Distribution on Jupiter and Implications for Gas Giant Dynamics||The vertical distribution of trace gases in planetary atmospheres can be obtained with observations of the atmosphere's thermal emission. Inverting radio observations to recover the atmospheric structure, however, is non-trivial, and the solutions are degenerate. We propose a modeling framework to prescribe a vertical distribution of trace gases that combines a thermo-chemical equilibrium model based on a vertical temperature structure and compare these results to models where ammonia can vary between pre-defined pressure nodes. To this means we retrieve nadir brightness temperatures and limb-darkening parameters, together with their uncertainties, from the Juno Microwave Radiometer (MWR). We then apply this framework to MWR observations during Juno's first year of operation (Perijove passes 1 - 12) and to longitudinally-averaged latitude scans taken with the upgraded Very Large Array (VLA). We use the model to constrain the distribution of ammonia between -60 and 60 deg latitude and down to 100 bar and address the implications for the atmosphere of Gas Giants in general.||Anton Ermakov|
|31-Aug||Barbara Romanovicz||In person||UCB||A voyage through the Earth's Deep Interior||Sixty years ago, the plate tectonics revolution brought to light the dynamic nature of the earth's interior, with rising hot molten rock forming new crust at mid-ocean ridges and cold, thickened tectonic plates returning to the mantle at so-called subduction zones. We now understand that plate motions are driven by internal currents of matter that serve to evacuate heat accumulated deep in our planet at the time of its formation, or through persistent decay of radioactive elements scattered within it. However, the precise mechanisms by which these motions interact with plates remains somewhat elusive.|
Seismic waves generated by natural earthquakes penetrate deep into the earth's interior, accelerating or decelerating as they propagate, depending on the temperature and composition of the rock masses they encounter, thus illuminating the internal structure of our planet. Global scale seismic imaging allows us to map out, at progressively higher resolution, the morphology of the slow convective motions within the earth's mantle that drive plate tectonics, ultimately causing earthquakes and volcanic eruptions. I will illustrate how state-of-the-art imaging techniques inform our evolving views of the state and global dynamics of the earth's mantle, allowing us to track the fate of tectonic plates beneath the Pacific "ring of fire", and to follow the paths of deeply rooted hot mantle plumes, as they ascend towards the surface and feed hotspot volcanoes, of which Hawaii and Iceland are prominent examples.
|7-Sep||Chris O'Connor||In person||Cornell||White-dwarf planetary systems: origins of short-period companions and metal pollution||The planetary systems of white dwarfs (WDs) are fertile ground for insight into the physical properties and dynamical evolution of planetary systems more generally. I will discuss some recent progress in understanding the final stage of a planetary system's life cycle from both theoretical and observational perspectives. In the first part of the talk, I will introduce the system WD1856+534 and its short-period giant planet; I will summarize the two leading hypotheses for its dynamical history and remark on how this system probes poorly understood planet-star interactions. In the second part, I will discuss the origins of metal pollution in WD atmospheres, a common signature of remnant planetary systems. What is the nature of the parent bodies of pollution? What dynamical mechanisms deliver them to the WD, and how does this constrain the properties of distant, as-yet-unseen surviving planets? Where applicable, I will highlight upcoming JWST programs dedicated to WD planetary science.||Burkhard Militzer, Anton, JJ|
|14-Sep||Akash Gupta||Zoom||UCLA||From the galactic to atomic scale: understanding planet formation and evolution||One of the most profound findings from NASA’s Kepler mission was the unexpected dearth of close-in exoplanets of sizes 1.5 to 2.0 Earth radii, i.e., a radius valley. This valley divides the population of the most abundant class of planets yet known, those between the sizes of Earth and Neptune, into small planets with Earth-like compositions and large planets with hydrogen-rich atmospheres or ice-rich interiors. Recently, we demonstrated that atmospheric mass-loss driven by the cooling luminosity of a planet and its host star's bolometric luminosity can explain this observation, even in the absence of any other process. In this talk, I will describe the key physical processes driving this core-powered mass-loss mechanism. I will present how our results compare with observations and the testable predictions we make as a function of planet and host-star properties. This will include sharing our latest work on the characteristics of the radius valley around M dwarfs.
One of our significant findings is that most observed exoplanets have hydrogen atmospheres interacting with molten or super-critical interiors for millions to billions of years. In our Solar system, we see this for planets such as Jupiter and Uranus. Studies show that such interactions can have far-reaching implications for an atmosphere’s composition, structure, and evolution. However, we hardly understand these interactions, and studying them in a laboratory is difficult. I will discuss how we address this problem using quantum mechanical molecular dynamics. Specifically, I will share the findings of our upcoming work on the solubility of a planet's hydrogen atmosphere in its super-critical water interior and their implications for planets and exoplanets such as Uranus.
|21-Sep||Walter Alvarez||In person||UCB||The Chicxulub impact and dinosaur extinction: extreme improbability in integrative planetary science||The discovery of the Chicxulub crater in Mexico’s Yucatán Peninsula, the largest known impact structure formed on Earth during the last couple of billion years, started with the study of limestones in the Apennine Mountains of Italy for completely unrelated reasons. The research began and continued here in Berkeley.|
Extreme improbability is a useful lens with which to investigate history – both human history and Earth history. Now that we know of several thousand extrasolar planets, only a tiny fraction of which appear to provide conditions suitable for the evolution of intelligent life, it may be the time to consider extreme improbability in integrated planetary science as well.
The Chicxulub story will be recounted here with particular emphasis on how extremely improbable the whole sequence of events was – both the discovery of Chicxulub itself and the improbability of that impact event ever having happened at all. Hopefully there will be time at the end for a discussion of how the improbability concept might be quantified and used in integrative planetary science.
|28-Sep||Tanja Kovacevic||in person||UCB||Using Ab Initio Simulations to Investigate the Miscibility of Rock and Ice within Water Worlds||Water worlds are exoplanets more massive than Earth that contain a significant amount of water overlaying a rocky mantle and iron core. Characterizing the interactions between water and rock under the pressures and temperatures within water worlds is essential to understanding their structure, formation, and evolution. We studied the dynamics of water and high-pressure MgSiO3, a major silicate phase at pressures ranging from 30-120 Gpa and temperatures from 500-8000 K. Our results demonstrate that MgSiO3 and water are miscible in all proportions when the temperature exceeds the melting point of MgSiO3. Giant impact simulations were run using smoothed particle hydrodynamics to confirm that the conditions for rock-water miscibility were reached. We found that rock and water become miscible within the interiors of water worlds during their collisional growth, forming a fuzzy, mixed layer increasing the amount of water incorporated deep within the planet.||Ned Molter|
|28-Sep||Erin Redwing||in person||UCB||Detecting Complex Biomolecules at the Plume of Enceladus Using Fluorescence Spectroscopy||This presentation proposes a new life detection mission concept for the outer Solar System. Using preliminary radiative transfer calculations, it is shown that a small spacecraft with a UV laser and fluorescence spectrometer could detect the distinctive signal of aromatic amino acids – particularly tryptophan. Tryptophan, a complex amino acid essential to proteins in Earth-life, fluoresces strongly when excited at UV wavelengths. Though Enceladus' ocean sits beneath a layer of ice, it is possible to gain insight into its contents by observing the south polar plumes, which spew water vapor from the ocean to the surface. A spacecraft equipped with a UV laser and spectrograph could observe the fluorescence of tryptophan in and around the plume of Enceladus during a fly-by, and therefore confirm the presence of complex biomolecules. This talk will discuss the viability of this detection method for plausible fly-by mission scenarios using back-of-the-envelope radiative transfer calculations, which seek to identify limitations on the laser power, distance, and tryptophan concentration required for detection in plume vapor and the surrounding surface snow-pack material, and provide instrumentation recommendations for future missions to Enceladus.||Ned Molter|
|5-Oct||Brendan Bowler||In person||UT Austin||Dynamical Beacons: Probing the Outer Architectures of Planetary Systems with Accelerating Stars||Planets show a remarkable diversity spanning over four orders of magnitude in mass, orbital separation, and age. High-contrast adaptive optics imaging has opened up much of this landscape at wide separations where multiple models of planet formation are expected to operate, but disentangling specific formation routes requires larger samples and better orbit constraints. Precision astrometry offers a novel way to find and characterize long-period planets by measuring the reflex motion induced on a host star by its companion. In particular, Hipparcos and Gaia together have the precision and baseline to detect astrometric accelerations from long-period brown dwarfs and giant planets. I will present early discoveries, dynamical masses, and precise orbit constraints from an ongoing high-contrast imaging campaign targeting accelerating stars. Together these systems are providing rare tests of low-temperature evolutionary models across a broad range of masses, ages, and luminosities. Looking forward, this survey and search strategy will yield some of the best-suited targets for future deep observations with JWST and the ground-based ELTs.||Jointly hosted by Paul Kalas and JJ|
|12-Oct||Marta Bryan||In person||UCB||Exo-Jupiters: The Movers and Shakers of Planetary Systems||Understanding what formation processes produce the extraordinary diversity of planetary systems that we see today is one of the driving questions in the field. Of all the new planets that have been discovered, gas giants are the easiest ones for us to find – they are bigger, brighter, and more massive than any other kind of planet. This means that they are ideal targets for characterization techniques that can tell us about the planet formation process, and they are so massive that they dominate the dynamics of their systems, impacting the formation of other planets. Gas giants are an obvious place for us to start if we want to learn about the physics of planet formation. In this talk I will describe my work using multiple observational techniques to explore the formation and evolution of gas giants. I will discuss how targeting directly imaged planets with high-resolution spectroscopy enables measurements of new planetary properties like rotation rates, obliquities, and detailed atmospheric abundances. These provide fundamental insights into the physics of gas giant formation, such as the evolution of planetary angular momentum. I will also talk about how radial velocity searches for Jupiter analogs in systems with known inner planets reveal the impact gas giants have on the inner architectures of planetary systems, and are a key step in the search for life on other planets. Finally, I will briefly highlight the important role that new instrumentation and next-generation 30-meter telescopes will have in extending these high-resolution spectroscopy measurements to directly imaged ice giant and terrestrial worlds, opening new windows into their formation histories.||Burkhard Militzer|
|19-Oct||Marzia Parisi||Zoom||JPL/Caltech||Inside Jupiter: what Juno gravity soundings taught us about the gas giant's interior during the Prime Mission.||The Juno spacecraft has completed its Prime Mission in the Jovian system, after about 5 years of orbiting Jupiter. The 33 closest approaches to the planet (or perijoves) occurred at altitudes as low as 4,000 every 53 days. Since orbit insertion on July 4th 2016, the extensive Juno observations have provided outstanding discoveries regarding the magnetosphere, atmosphere and interior structure of Jupiter. Specifically, the gravity sounding of the planet is performed by measuring the Doppler shift on the Juno radio-frequency carriers in X- and Ka-band. In turn, these are converted into measurements of the gravitational moments, which are used to probe the atmospheric dynamics and deep density distribution within the planet. This seminar will report on the current status of the gravity estimates, providing an overview of what we have learnt so far about the deeper layers of Jupiter by looking at the planet's gravity field.||Anton Ermakov|
|26-Oct||Daniella DellaGiustina||Zoom||U of Arizona||OSIRIS-APEX: An OSIRIS-REx Extended Mission to Asteroid Apophis||The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft mission characterized and collected a sample from asteroid (101955) Bennu. After the OSIRIS-REx Sample Return Capsule is released to Earth's surface in 2023, the spacecraft will divert into a new orbit that encounters asteroid (99942) Apophis in 2029, enabling a second mission with the same unique capabilities: OSIRIS–Apophis Explorer (APEX). On April 13, 2029, the 340-m-diameter Apophis flies within ~32,000 km of Earth's surface, <1/10th the lunar distance. Apophis will be the largest object to approach Earth this closely in recorded history. This rare planetary encounter will alter Apophis' orbit, subject it to tidal forces that change its spin state and may seismically disturb its surface. APEX will distantly observe Apophis during its Earth encounter and capture its evolution in real-time, revealing the consequences of an asteroid undergoing tidal disturbance by a major planet. The spacecraft's instrument suite will subsequently provide high-resolution data of a "stony" asteroid—advancing knowledge of these objects and their connection to meteorites. Near the mission's end, APEX will perform Regolith Excavation by S/C Thrusters; a technique demonstrated at Bennu. Observations during and after excavation will provide insight into the material properties of stony asteroids. Furthermore, Apophis' material and structure have critical implications for planetary defense.||Anton Ermakov|
|2-Nov||Orkan Umurhan||In person||NASA-ARC and SETI||Forming the first planetesimals: finding the way to the promised land||The formation of planetesimals during the first million years of the solar nebula remains confounding to the theorist. In this talk I will review the current state of understanding and various open issues regarding the problem of gas-particle dynamics in protoplanetary disk modeling. Topics that will be discussed include a survey of planetesimal formation mechanisms, like the streaming instability and turbulent concentration, and under what realistic disk environmental conditions they are expected to operate most efficiently. I will also discuss the importance of properly characterising disk turbulence in order to better resolve the fate of growing particles followed by ideas about the way forward.\||Burkhard Militzer|
|9-Nov||Jakob Robnik||In person||UCB||Probabilistic Exoplanet Search||Despite all the significant successes of the Kepler space telescope, it falls one important goal short - the characterization of habitable zone planets. This is because habitable zone planets are buried below the noise level of several unexpected false positive scenarios|
I will introduce a probabilistic exoplanet search below the noise level, where all sources of false positives, such as outliers and stellar variability, are modeled statistically. Demographics of physically interesting false scenarios, such as eclipsing binaries, heartbeat stars, and compact object lenses, are studied together with the exoplanet demographics. The improved modeling significantly reduces the number of false detections and unveils a fainter signal. I will also present a null search with modified exoplanet transit templates, which quantifies the residual false positive rate.
All the probabilistic information from individual planet candidates can be used to quantify the planet probability distribution using a hierarchical Bayesian analysis. This analysis will quantify planet demographics as a function of variables such as stellar type, planet period, radius, and orbit eccentricity.
|16-Nov||Katherine de Kleer||Zoom||Caltech||The Surface Heterogeneity of Thermally-Evolved Asteroids from ALMA||The early heating of planetesimals led to differentiation of larger objects into cores, mantles, and crusts. Subsequent collisions disrupted these objects, leaving fragments of different compositions and likely a residual parent body with large-scale heterogeneities due to exposure of interior layers. These objects remain today in the asteroid belt, giving us a window into early Solar System differentiation and collisional processes. With ALMA, it is now possible to directly resolve asteroids and map their compositional heterogeneity to gain insight into these processes. We have recently begun a program to survey a set of large asteroids spanning a range of compositional classes in high-resolution thermal emission and polarization with ALMA. The first target in the survey is the asteroid (16) Psyche, which has been thought to be the remnant core fragment of a differentiated planetesimal and is the target of the upcoming Psyche mission. In this talk, I will present results from our study of (16) Psyche, and will describe what we hope to learn from the future targets, for which data will be obtained in 2023.||Anton Ermakov|
|30-Nov||Kazumasa Ohno||Zoom or in person||UCSC||Jupiter in the context of Atmospheric Characterization of Exoplanets||Planetary atmospheres offer valuable clues to the past formation and evolution history of planets. Recent studies suggested that Jupiter might originally form at >30 AU because of its enriched atmospheric nitrogen and noble gasses. I will first talk about the importance of the shadows of protoplanetary disk substructures for inferring the planet formation process from atmospheric observations. In particular, I will discuss that the disk shadow may be a key to understanding why the Jovian atmosphere is enriched in highly volatile nitrogen.|
Atmospheric nitrogen is the main driver of the discussion of Jupiter formation, and it would motivate us to search for nitrogen in exoplanets. While nitrogen species, such as NH3, will be accessible by JWST for exoplanetary atmospheres, it is not straightforward to constrain the bulk nitrogen abundance, as the nitrogen chemistry is susceptible to disequilibrium processes. In the second part of the presentation, I will discuss suitable planetary properties and observational feasibility of nitrogen species in exoplanetary atmospheres based on semi-analytical argument and series of photochemical calculation.
Solar system giant planets commonly possess circumplanetary rings, while it remains unclear how common the ring is in exoplanetary systems. In the rest of the talk, I will discuss how the circum exoplanetary ring may affect atmospheric observations of exoplanets, with focusing on temperate giant planets HIP41378f and young 10 Myr exo-Neptune K2-33b.
|7-Dec||Damya Souami||In person||Observatoire de la Côte d’Azur, Nice||Burkhard Militzer|
|14-Dec||No seminar - AGU|