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1 | CIPS - Planetary Science SEMINARS - Spring 2025 | |||||||
2 | Campus and bay-area speakers will present in person. Remote speakers will present over Zoom. | |||||||
3 | 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 | |||||||
4 | For a Zoom link to the meeting please contact: militzer @ berkeley . edu | |||||||
5 | Recordings from past presentations can be found here: https://drive.google.com/drive/folders/1it7b0Z_QRXCAktz-szIShkR1-2L0oO72?usp=sharing | |||||||
6 | Date | Speaker | Zoom/In person | Affiliation | Title | Abstract | Host | |
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8 | 22-Jan | Gwen Hanley | In person | UCB/SSL | Carbon escape at Mars is enhanced during space weather events | Mars' dayside ionosphere is maintained primarily by ionization from solar ultraviolet photons and subsequent chemical reactions, with small contributions from other mechanisms such as impact ionization and charge exchange. In December 2023, the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission observed the impact of an interplanetary coronal mass ejection (ICME) on Mars' space environment, including strongly enhanced fluxes of suprathermal electrons. This enhancement in suprathermal electron fluxes increased ion production from electron impact, so that dayside electron impact ionization rates at high altitudes exceeded photoionization rates in some regions during the ICME. This change in ion production mechanisms led to unusually high densities of the minor ions C+ and O++. Space weather events are known to increase ion escape rates, so changes in ion composition during space weather events have important implications for atmospheric evolution. We show that scaling nominal loss rates to account for space weather events may underestimate carbon loss from Mars' atmosphere on geologic timescales. The fraction of atmospheric escape that occurs as ions is not the only important quantity for understanding atmospheric escape and planetary habitability in the context of space weather: the composition of that escape also matters, and may be overlooked in current models. | Paul Szabo | |
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10 | 29-Jan | Felipe González Cataldo | In person | UCB/EPS | From Super-Earth Cores to Dissolving Gas Giant Interiors: A Quantum and Material Science Journey Through Planetary Extremes | Understanding the interiors of exoplanets, particularly Super-Earths and Sub-Neptunes, requires bridging the gap between observations of planetary atmospheres and the physical properties of materials under extreme conditions. Using first-principles simulations, we can predict the behavior of planetary materials at pressures and temperatures far beyond experimental reach. These approaches enable the development of comprehensive equations of state (EOS) and reveal phase transitions, mixing behaviors, and material properties critical for interpreting planetary structure and evolution. In this talk, I will discuss how our simulations provide insights into the composition and structure of exoplanets, evolution of their cores, and novel chemistry of rock-ice mixtures in their mantles. I will also address how the erosion of gas giant cores can affect their atmospheres. By combining cutting-edge simulation techniques with observational constraints, we aim to improve our understanding of planetary formation and evolution. | Paul Szabo / Mei-Yun Lin | |
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12 | 5-Feb | Emmanuel Dormy | In person | ENS, Paris | Rapidly Rotating Magnetohydrodynamics and the Geodynamo | The problem of the Geodynamo is simple to formulate (Why does the Earth possess a magnetic field?), yet it proves surprisingly hard to address. As with most geophysical flows, the fluid flow of molten iron in the Earth’s core is strongly influenced by the Coriolis effect. Because the liquid is electrically conducting, it is also strongly influenced by the Lorentz force. The balance is unusual in that, whereas each of these effects considered separately tends to impede the flow, the magnetic field in the Earth’s core relaxes the effect of the rapid rotation and allows the development of a large-scale flow in the core that in turn regenerates the field. In this seminar, I will review some recent developments regarding the interplay between rotation and magnetic fields and how it affects the flow in the Earth’s core. | Bruce Buffett | |
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14 | 12-Feb | Paula Wulff | In person | UCLA | On the meaning of the dynamo radius in gas giants with helium rain | Current structure models of Jupiter and Saturn suggest the presence of a region where helium is immiscible in hydrogen in the outer part of the planets’ conducting regions. This phenomenon is likely to inhibit convection. The presence of such a convectively stably stratified layer will impact where and how the convectively-driven interior dynamo action occurs. Thus, the existence and structure of the helium rain layer may prove essential for our understanding and interpretation of the magnetic field morphology of the two planets. Juno’s measurements of Jupiter’s magnetic field now extend to the first 18 degrees of its spherical harmonic spectrum. This external potential field data enables an estimate of the jovian Lowes radius, which is an estimate of the dynamo radius derived from the Lowes spectrum of the planet. A depth of around 0.8RJ is obtained, where RJ is Jupiter’s radius. This result is rather deep, considering the electrical conductivity becomes significant below ∼ 0.9RJ. I use 3D numerical MHD simulations to explore the effect of the existence, and location, of a stably stratified helium rain layer on both the inferred Lowes radius and physical location of the outermost radial extent of dynamo action for models with different internal magnetic fields. I focus on a Jupiter-like internal structure and electrical conductivity profile. I find that for shallower helium rain layers, there is no magnetic field generation occurring above the helium rain layer and the effective dynamo radius is at the base of the layer. For deeper dynamos, their surface spectra lead to inferred dynamo radii of around 0.86 jupiter radii as a shallow secondary dynamo operates above the stable layer. | Phil Marcus | |
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16 | 19-Feb | Greg Herczeg | in person | Peking University | Protostellar Variability and Stellar Mass Assembly | Young stellar objects are notoriously variable. The largest amplitudes are seen on FU Ori objects, bursts of a factor of ~1000 in accretion rate that may last for centuries. However, the importance of such large bursts in stellar assembly remains uncertain. In this talk, I will discuss the role that variability plays at the different stages of evolution of young stellar objects and consequences for planet formation. I will highlight the JCMT Transient Program, the first dedicated sub-mm monitoring program, to measure the role of bursts in the earliest stages of stellar assembly, and discuss future prospects for protostellar monitoring. | J. J. Zanazzi | |
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18 | 26-Feb | Andrew Fisher | in person | UCSC | Sustaining low-to-moderate temperature hydrothermal circulation under ocean-world gravity. | Controls on sustainability of subseafloor hydrothermal circulation on ocean worlds are not well understood. We developed three‐dimensional numerical simulations, using a ridge‐flank hydrothermal system on Earth as a reference, to test the influence of ocean world gravity on metrics for hydrothermal fluid and heat transport. Simulations represented ∼4-5 km of a silicate core below an ocean, and explored the influence of: heat input at the domain base; aquifer thickness, depth extent, and permeability; and gravity values appropriate for Earth, Europa, and Enceladus. Calculations illustrate a trade‐off between reduced buoyancy at lower gravity and the concomitant reduction in secondary convection; the latter process saps driving energy and thereby reduces circulation sustainability. Simulations that sustained hydrothermal flow achieved reaction and discharge temperatures ≤150 °C, flow rates ≤2,100 kg/s, and heat output ≤700 MW. Lower gravity tended to increase vent fluid temperatures while reducing mass flow rates and advective heat output. Deeper circulation tended to increase temperatures and flow rates, with a deeper, thin aquifer being more efficient in removing heat from the rocky interior than either a shallow-thin or a deep-thick aquifer. Water‐rock ratios were lower at lower gravity, all else being equal, whereas the time required to circulate the volume of an ocean‐world's ocean in and out of the seafloor was greater. This may help to explain how small ocean worlds could sustain hydrothermal circulation for a long time despite limited heat sources. We are currently extending these simulations across a broader range of free parameters using a simplified analytical framework, allowing Monte Carlo exploration of conditions consistent with sustaining a hydrothermal siphon on an ocean world, including gravity values greater than that for Earth. Initial results with this approach replicate key numerical results and point to areas for future numerical exploration. | Phil Marcus | |
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20 | 5-Mar | Cheng Li | in person | University of Michigan | Origins of Hemispheric Asymmetry on Ice Giants | Giant planets in our solar system are divided into gas giants and ice giants. The gas giants are mainly made of hydrogen and helium with tracer amount of water and other volatile species. Ice giants have significantly higher amounts of heavy elements while still keeping a hydrogen and helium envelope. Since the Voyager era, space- and ground-based observations have tracked Uranus' seasons from one solstice to the next. The variation in temperature across latitudes in the troposphere and lower stratosphere appears largely insensitive to seasonal changes, suggesting an internal mechanism controlling the temperature structure. We investigate the cause of hemispheric asymmetry driven by internal mechanisms, such as internal heat, and find that asymmetry emerges when the equatorial jet is retrograde, whereas it disappears when the equatorial jet is prograde. Our model explains why the polar regions of ice giants often exhibit strong brightness temperature contrasts, unlike gas giants. Previously, these hemispheric differences were attributed to the depletion of volatile gases; however, our model suggests that the temperature structure may also play a significant role on ice giants. | Phil Marcus | |
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22 | 12-Mar | Daria Holdenfried-Chernof | in person | UCB/EPS | Variability in turbulent fluids and the Earth’s dynamo | The Earth’s magnetic field is known to have undergone numerous polarity reversals in the past, but the mechanism by which these reversals occur remains unclear. As a first step towards understanding the physical processes leading to reversals, we have developed a stochastic framework to study a field’s statistics as a function of the statistics of the underlying turbulent fluid flow. The magnetic field’s variability is a key quantity for better understanding the reversal rate, but it is challenging to compute. In this talk I will present results restricted to considering the variability of scalar field satisfying a convection-diffusion equation in a turbulent flow. Using the temperature field as a test case, we compute its maximal average variability and the time scale when this is achieved. These results constitute useful stepping stones to unravelling the behaviour of geomagnetic reversals. | Phil Marcus | |
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24 | 19-Mar | Jonathon Aurnou | in person | UCLA | Tabletop Atmospheric Rivers | Large-scale atmospheric and oceanic fluid dynamics are dominated by the effects of planetary rotation and, thus, differ fundamentally from the local-scale fluid motions that we are well acquainted with. In this talk, we will carry out a simple, DIY rotating tank experiment to generate a tabletop atmospheric jet stream. The instability of this jet takes the scaled-down form of midlatitude winter-time storm systems with analog atmospheric rivers tending to wrap around their peripheries. Thus, assuming the desktop experimental powers-that-be are beneficent and that I can get my experiment through LAX security, then the chance will be had to demonstrate and explain some of the essential phenomena of winter-time west coast climate. | Phil Marcus | |
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26 | 26-Mar | Spring break - no seminar | ||||||
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28 | 2-Apr | Hao Cao | in person | UCLA | Are Mercury and Ganymede Magnetic Twins? | The smallest planet, Mercury, and the largest moon, Ganymede, in the solar system are both magnetized. Ganymede’s surface magnetic field is stronger than Mercury’s, yet neither of these fields appears to be compatible with our current understanding of homogenous dynamo action. In this seminar, after reviewing the different dynamo hypothesis proposed for Mercury’s magnetic field, I will present our numerical dynamo investigation of a unique scenario for Mercury’s core: a double iron-snow regime in which iron-rich solids nucleate simultaneously near the core-mantle boundary (CMB) and at mid-depth inside the outer core. The resultant flow, magnetic field, and the implications for the core composition of Mercury will be discussed. Finally, I will conclude by highlighting how upcoming magnetic field measurements from the ESA JUICE mission orbiting Ganymede can provide critical data to map out the boundaries between different dynamo regimes. | Phil Marcus | |
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30 | 9-Apr | Matthew Belyakov | in person | Caltech | Giant Planet Irregular Satellites with JWST | Dynamical instability models for early Solar System evolution predict a shared origin for the Irregular satellites of the giant planets, the Jovian and Neptunian Trojans, and the Kuiper Belt. However, the observational evidence for this connection remains sparse. I will present the JWST spectra of the giant planet irregular satellites, seeking to reconcile their unexpected compositional diversity with the prediction of their capture from the same population that later formed Kuiper belt. | ||
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32 | 14-Apr | Masafumi Imai | in person | Czech Acad. Sci. | Polarization measurements of Saturn electrostatic discharges during the Voyager era | Saturn Electrostatic Discharges or SEDs are electromagnetic radio emissions caused by lightning discharges in Saturn's atmosphere. They were first detected by both Voyager spacecraft during their Saturn flybys in November 1980 and August 1981, respectively. In this study we reinvestigate the SED wave polarization, since previous studies were inconclusive. Our polarization study is the first which properly considers the characteristics of the Voyager Planetary Radio Astronomy (PRA) instrument and the change of the antenna response as a function of spacecraft attitude. SED observations of the Cassini spacecraft from 2004 until 2017 showed a dependence of the polarization sense below a frequency of 2 MHz on the hemispherical location of the causative lightning storm. Their circular polarization sense was left-handed for storms in the northern hemisphere and right-handed for storms in the southern hemisphere. For Voyager we found mixed polarizations and a dominance of right-handed SEDs. This is difficult to explain in view of the Cassini results and in view of Voyager imaging observations detecting convective cloud features at a latitude of 35°North. Using a model simulation of the Voyager signal processing of short pulses we found that mixed polarizations are possible, and we also found that only SEDs from sources at large elevation angles from the antenna plane (above 40°) showed a dominance of the expected left-handed polarization sense. In this talk, we present results of the SEDs associated with the optical cloud images during the Voyager era. | Mike Wong | |
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34 | 16-Apr | Daniel Lecoanet | in person | Northwestern | Model Hierarchies for Understanding the Quasi-Biennial Oscillation | Small-scale fluid processes underlie many phenomena in planetary science, from cloud feedbacks, to turbulent mixing, to wave dynamics. They can have significant influence on large scales, and are typically parameterized in global models. Here I will use a hierarchy of models of small-scale fluid dynamics to test different conceptual theories of the processes. I will apply this strategy to study wave-mean flow interactions, which are known to drive large-scale atmospheric winds on Earth, known as the Quasi-Biennial Oscillation, as well as other planets. The different models are simulated using the Dedalus simulation code, which can solve nearly arbitrary partial differential equations using spectral methods. Testing different theories using this type of model hierarchy leads to a deeper understanding of the underlying processes, which can be used to develop robust parameterizations. | ||
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36 | 23-Apr | Raul Morales Juberias | in person | New Mexico Tech | Towards a better characterization of the 3D winds and vortex dynamics in Jupiter | The atmospheres of the gas giant planets represent a natural laboratory in which to study the dynamics of rotating flows under different conditions. These atmospheres are dynamically characterized by a series of alternating eastward and westward zonal jets. Embedded between these jets, we find vortices that also move predominantly in the zonal direction. Here we will present progress made towards measuring 3D flows in Jupiter?s atmosphere from ground-based telescopes using a Doppler velocimeter. We will also present comparative results of the motion of vortices in two of the most densely populated areas of Jupiter and in the equatorial region of Neptune. | Phil Marcus | |
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38 | 30-Apr | Abigail Flom | in person | University of Hawaii | Lunar Eclipses as a Tool to Investigate Temperature-Driven Variability in the 3 um Hydration Band | A common view of the moon as inherently dry abruptly changed with the detection of a widespread 3 um spectral absorption band by three separate instruments. The 3 um absorption band indicates the presence of hydroxyl and/or water (collectively referred to as hydration). The mechanisms for the formation, loss, and transport of these volatiles are important for the scientific interest of understanding the volatile reservoirs of airless bodies and the implications for in situ resource utilizations for future missions and human exploration. However, there is disagreement about the interpretation of this band and how the global distribution of hydration relates to temperature. In this study, I leverage the unique thermal environment during lunar eclipses to examine how the 3 µm absorption feature responds to rapid temperature changes. Telescopic observations reveal a dynamic evolution of the band, challenging existing hypotheses about the origin and mobility of lunar hydration. | Ramana Sankar | |
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40 | 7-May | Andrea Zorzi | in-person | Stanford | Effect of impacts on the evolution of life on terrestrial planets | Impacts play a key role in shaping the atmospheric composition of rocky planets by delivering species to primordial atmospheres, affecting planetary habitability. During the seminar, I will focus on two ways impacts influence the evolution of a biosphere: climate perturbation and production of prebiotic species. First, I will present a modeling framework to quantify the impact-induced climate perturbation, occurring when climatically active gases are produced from vaporization of target material. We tested whether impacts induce hypethermal events on Earth by quantifying the global temperature increase associated with impacts via the release of CO2 and CH4 sourced from target rocks into the atmosphere. Our results suggest that small (<2 km diameter) impactors associated to past global warming events were too small to have induced hyperthermal-like (>1 K) temperature changes. >10 km diameter impactors may produce hyperthermal events, but such large impacts are predicted to be uncommon during the Cenozoic era (2–4 objects per Gyr). Second, I will investigate the production of prebiotic species formed in-situ from reactions induced by shock-heating upon formation of the impact vapor plume and its interaction with the atmosphere. I will present a new model to treat the plume/atmosphere interaction accounting for disequilibrium chemistry. Results will be shown for the production of prebiotic molecules (HCN, CH4, NH3) for different impact scenarios, varying kinetic energy of the impactor, atmospheric surface density and composition. We find that prebiotic species are produced on Earth-like planets with a N2-CH4 atmosphere. Molar fractions for methane and ammonia increase with impact energy, while hydrogen cyanide is depleted for more energetic impacts. Moreover, we find that plume-atmosphere mixing affects prebiotic species abundances, leading to 2-4 orders of magnitude difference compared to when mixing is neglected. Our findings provide necessary but not sufficient conditions for prebiotic chemistry to start, to assess the astrobiological potential of impacts on terrestrial worlds. | Mei-Yun Lin | |
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42 | 14-May | Finals week - no seminar | ||||||
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