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1 | Planetary Science SEMINARS - Spring 2023 | |||||||
2 | Campus and bay-area speakers will present in person. Remote speakers will present over Zoom. | |||||||
3 | Wednesdays 1:10-2:00 PM | |||||||
4 | For a Zoom link to the meeting please contact: militzer @ berkeley . edu | |||||||
5 | Date | Speaker | Zoom / in person | Affiliation | Title | Abstract | Host | |
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7 | 18-Jan | Marius Millot | in person | LLNL | Fusion and Planetary Science Experiments at the National Ignition Facility | The National Ignition Facility (NIF) in Livermore – the world’s most energetic laser system – provides enormous amounts of energy with exquisite control and full suites of advanced diagnostics which enable us to compress matter to the extreme conditions existing deep inside planets and stars. I will briefly review recent progress in Inertial Confinement Fusion (ICF) research leading to the demonstration that NIF implosions can produce more fusion energy from Deuterium-Tritium fusion reactions than the laser energy that was used to drive the target—that is a target energy gain G>1 [1]. This milestone caps more than 50 years of research [2] and technological development at Lawrence Livermore National Laboratory and enables the realistic development of ICF approaches to Inertial Fusion Energy (IFE) to deliver nuclear fusion power to the grid in the next few decades. The versatility of the NIF can also be exploited to perform dynamic compression experiments to recreate planetary relevant extreme conditions in the laboratory. We can now investigate how the extreme pressures and temperatures typical of planetary interiors and giant impacts modify the physical and chemical properties of constituent materials to provide robust foundations for integrated studies of the physical origin and geochemical evolution of planets and planetary systems. Using nanosecond diagnostics, we can document the atomic structure and the equation of state (EOS), reveal changes in the optical and electrical properties and explore new exotic states of dense matter. I will discuss recent experimental results including the discovery of superionic water ice which could dominate the interior of icy planets [3,4] and the demixing of hydrogen and helium at Jovian planet conditions [5]. Prepared by LLNL under Contract DE-AC52-07NA27344. [1] https://www.energy.gov/articles/doe-national-laboratory-makes-history-achieving-fusion-ignition. [2] Zylstra, A., et al., Burning plasma achieved in inertial fusion, Nature601 542-548 (2022). [3] Millot, M., et al. Experimental evidence for superionic water ice using shock compression, Nat. Phys. 14, 297–302 (2018). [4] Millot, M., et al. Nanosecond X-ray diffraction of shock-compressed superionic water ice, Nature 569, 251–255 (2019). [5] Brygoo, S., et al. Evidence of hydrogen−helium immiscibility at Jupiter-interior conditions, Nature 593, 517–521 (2021). | Burkhard Militzer | |
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9 | 25-Jan | Damya Souami | in person | Visiting UCB from CNRS | Pushing the limits of stellar occultations to probe small Near Earth Asteroids | The powerful method of stellar occultations is an unbeatable technique uniquely approaching, in some aspects, the performances of planetary space missions. It allows km-level accuracies on the determination of shapes and sizes of objects. Furthermore, it allows to derive, using small aperture telescopes, asteroid positions at Gaia-level accuracy, extending the time-coverage of Gaia. Although challenging, occultations by NEAs and in particular by sub-km NEAs are feasible under some conditions. They require an initial astrometric follow-up to predict reliable occultation events. They also require the deployment of mobile stations equipped with fast cameras across the prediction path. For most our targets, the maximum expected duration of the event is <0.5 s. I will present here the strengths and limitations of such an approach as well as preliminary results obtained over the last few month, in particular in the case of (65 803) Didymos to support both the DART (NASA) and Hera (ESA) planetary defence missions. | Ned Molter | |
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11 | 1-Feb | Benjamin Idini | in person | UCSC | Dynamical tides: Juno observations and future missions. | Dynamical tides are typically hypothesized to generate the tidal dissipation that drives the orbital migration of the Galilean satellites. Until recently, direct evidence of these tides remained elusive. In this talk, I will present the first direct detection of dynamical tides in a gas giant planet derived from NASA’s Juno mission observations of Jupiter’s tidal response. I will further present my contributions to developing a theory of dynamical tides capable of connecting Jupiter’s tidal response to its interior structure. As part of this effort, I will discuss an interpretation of Jupiter’s high-degree tidal response proposed to represent the resonant effect of waves trapped in the recently hypothesized dilute core of Jupiter. I will end my talk discussing potential applications of dynamical tides to the study of Europa and Ganymede from future missions Europa Clipper and JUICE, respectively. | Anton Ermakov | |
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13 | 8-Feb | Jennifer Bergner | in person | UCB | Volatile chemistry in planet-forming disks | Planets form within disks composed of gas, ice, and dust in orbit around young stars. The distribution of volatiles (gas+ice) within these disks profoundly impacts both the chemical and physical outcomes of planet formation-- including the delivery of prebiotic building blocks to new worlds. In this talk, I will highlight our recent advances in disentangling how organic complexity is built up during the star and planet formation sequence, the role of interstellar inheritance in setting disk volatile compositions, and the distinctive volatile chemistry at play during the planet formation epoch. These insights are gained by combining telescope observations, ice chemistry experiments, and disk simulations, each of which contributes an indispensable piece of the puzzle. Taken together, we are assembling a more complete picture of the chemical environment which regulates the formation, composition, and potential habitability of planetesimals and planets. | Burkhard Militzer | |
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15 | 15-Feb | Shane Carberry Mogan | in person | UCB/SSL | Callisto's Atmosphere | We explore the parameter space of the atomic hydrogen (H) observed by the Hubble Space Telescope in the atmosphere of Callisto, the outermost Galilean satellite of Jupiter. Our results indicate that sublimated water vapor (H2O) produced from the surface ice cannot explain the observed structure of the H. On the other hand, a global molecular hydrogen (H2) component can reproduce the observation, and is also capable of producing the electron densities observed at high altitudes by the Galileo spacecraft, thereby providing the first evidence of H2 in Callisto's atmosphere. We place rough upper limits on the amount of H2 required to reproduce these observations as well as on the peaks of H2O sublimation and the corresponding density, the latter constraints indicate previous models of Callisto’s atmosphere overestimated the abundance of H2O by at least 1-2 orders of magnitude. Finally, we discuss the importance of these results, particularly in the context of the other icy Galilean satellites, Europa and Ganymede, as well as of the forthcoming ESA JUpiter ICy moons Explorer (JUICE) mission. | Anton Ermakov | |
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17 | 22-Feb | Parke Loyd | remote | Eureka scientific | Probing Two Threads of the Star-Planet Connection: Magnetic Interactions and Coronal Mass Ejections | Extrasolar systems provide the opportunity to study the star-planet connection in new regimes, but also present unique observational challenges. I will discuss two forays into novel observations: one of a magnetic star-planet interaction and the other of stellar coronal mass ejections. Magnetic star-planet interactions (SPI) can reveal exoplanetary magnetic fields. Searching for such an interaction between the M dwarf star GJ 436 and its closely-orbiting Neptune-size planet exposed unusual stellar flares. This could be a previously unrecognized signature of magnetic star-planet interactions that merits investigation in other systems. In the GJ 436 system, the candidate SPI indicates a polar magnetic field strength < 100 G (< 7× Jupiter’s) for planet b. Turning to the second topic, stellar coronal mass ejections (CMEs) influence planetary atmospheric evolution, but few observational constraints exist. New constraints are possible through a CME signal identified on the Sun, coronal dimming. My collaborators and I developed a framework to probe CME masses with coronal dimming observations of stars. Applying it to the young solar-type star ε Eridani indicates ejections of > 1e15 g of 1 MK plasma occur at a rate no greater than 10× that of the Sun. | Ned Molter | |
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19 | 1-Mar | Szilard Gyalay | in person | UCSC | Searching for Sub-Surface Seas in Saturnian Satellite | Two of Saturn's satellites, Enceladus and Titan, are thought to contain sub-surface, global oceans beneath their icy crusts. Melting and maintaining an ocean requires significant internal heating. For instance, Enceladus' tidal bulge is raised by the difference in Saturn's gravitational pull across the moon, but will stretch and shift in response to periodic variation of this gravity gradient due to the orbit's ellipticity (eccentricity), ultimately generating heat by internal friction. Tidal heat can also be generated due to the tilt of a moon's spin axis (obliquity) or by radioactivity in its rocky mantle/core, the latter of which is expected to significantly contribute to Titan's internal heat. Importantly, how tidal heat varies spatially across the moon's interior depends on a few factors: whether the tides are due to eccentricity or obliquity, how deep the tidal heat is produced, and whether there is a sub-surface ocean. As such, if one assumes the spatial variation of tidal heating manifests as isostatic variations in ice shell thickness, one can use the observed long-wavelength topography (global shape) of an icy satellite to infer its tidal heating pattern and thus interior structure, including whether or not it contains an ocean. I apply the method to Tethys and Mimas and discuss the implications of their internal structures. | Anton Ermakov | |
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21 | 8-Mar | Anton Ermakov | in person | UCB/SSL | Ganymede's interior after Juno and before JUICE | We use the data from the Galileo and Juno missions to place constraints on Ganymede’s internal structure. Unlike in the previous studies, the hydrostaticity was not imposed on the degree-2 gravity coefficients, derived using combined Juno and Galileo datasets. The new gravity solution confirms the past detection of non-hydrostatic anomalies. Localized non-hydrostatic features with amplitudes four times higher than those found on Titan by the Cassini mission are identified, indicating that Ganymede’s interior can support larger non-hydrostatic stresses compared to Titan. Magnetic induction measured by Galileo provides a constraint on the ocean salinity and thickness. Finally, Juno Microwave Radiometer data provide a constraint on the global heat flux, which is sensitive to the thickness of the icy shell. We use Bayesian inference to exploit the full power of these data sets in informing Ganymede’s internal structure. | J. J. Zanazzi | |
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23 | 15-Mar | Feng Long | in person | University of Arizona | The ALMA High-resolution View of Planet-Forming Disks | How circumstellar disks evolve into planetary systems like and unlike our own Solar System is still one major open question. In recent years, ALMA’s unprecedented spatial resolution and sensitivity have transformed our understanding of planet-forming disks and the planet formation process. Disk substructures, often appearing as bright and dark emission rings, have been commonly detected with high-resolution ALMA observations. These rich disk substructures are widely taken as the imprints of interactions between young planets and the disk material, thus crucial to identifying key aspects of the planet formation process. In this talk, I will present recent efforts in exploring the emergence of disk substructures with a wide range of disk and stellar properties and thus constrain the planet formation conditions. In particular, I will report new findings in the LkCa 15 disk, where the detection of dust emission in horseshoe orbit provides compelling evidence for the presence of young planet. | J. J. Zanazzi | |
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25 | 22-Mar | Jessica Speedie | remote | Univ. of Victoria | Spiral wakes: Signposts of planets embedded in protoplanetary disks | High angular resolution ALMA observations of protoplanetary disks have revealed an abundance of spatial and kinematic substructures that may be interpreted as evidence for embedded planets. The hypothesis that these substructures are signposts of planets fundamentally relies on the existence of a planetary spiral wake, which is what enables a planet to open gaps, carve rings, and generate kinematic disturbances in the disk. Continuum detections of the spiral wake itself, however, have proven comparatively elusive. In this talk, I describe how we put ALMA to the test and quantified its ability to detect planet-driven spiral wakes in continuum emission under a wide range of disk conditions and observing setups. We then carried out the search in a strategically selected sample of real disks where the velocity “kink” kinematic signature of planetary spiral wakes has been previously detected. Our work provides an independent method to verify the existence of these kinematic planet candidates, and underscores the need for more simulation studies to understand how we can use planetary spiral wakes to detect the embedded planets that drive them. | J. J. Zanazzi | |
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27 | 29-Mar | Spring break - no seminar | remote | Title | Abstract | |||
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29 | 5-Apr | Prajkta Mane | in person | LPI | First Formed Solids: Records of the Earliest Times of the Solar System | Meteorites and their components can be used to unravel the history of the early Solar System. Carbonaceous chondrites are meteorites that originated from undifferentiated parent bodies that formed within a few million years of the beginning of the Solar System. These meteorites contain calcium-aluminum-rich inclusions (CAIs), which are the oldest dated solids forming in our Solar System at ~4.567 billion years old and thus preserve a record of the earliest stage of Solar System formation. The radiometric dating of these CAIs and other meteoritic components provides important time constraints on the events that occurred in the early Solar System, whereas textures and microstructures in these CAIs preserve the evidence of disk processes in them. In this talk, I will discuss results of a coordinated multi-technique approach to analyzing CAIs and their components to reveal the timescales and conditions of their formation. | Anton Ermakov | |
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31 | 12-Apr | Wanying Kang | remote | MIT | On icy satellites, size controls the ice geometry | Enceladus and Europa, two icy satellites in our solar system, share similar surface temperatures and mean ice thickness. Despite that, their ice shell geometries are likely to be very different. Gravity and shape measurements taken on Enceladus favor a strongly poleward thinning ice shell, whereas Europa’s ice shell seems to be much flatter, supported by its limb profile. This work proposes a mechanism to explain such a difference, which may be generalized to make predictions for other icy satellites. The key behind is the ocean dynamics. Driven by the temperature and salinity gradients underneath a thickness-varying ice shell, overturning circulations and baroclinic eddies will form, redistributing heat and tracers over the globe. The ocean heat transport (OHT) will, in turn, flatten the ice shell through the ice-pump mechanism. The efficiency of the OHT, however, varies with the satellite’s size and rotation period. In this work, we derive scaling laws that govern the OHT amplitude, verify the scalings using numerical simulations, and use them to predict the equilibrium ice thickness variations for icy moons with various sizes and rotation periods. Because of Europa’s strong gravity and slow rotation, its ice thickness variation is predicted to be less than 2km, in contrast to a 12+km ice thickness variation predicted for Enceladus. Given the OHT scaling laws, we demonstrate the possible ice evolution pathways for Enceladus and Europa using an ice evolution model with parameterized OHT. | Burkhard Militzer | |
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33 | 19-Apr | Robert Lillis | in person | UCB/SSL | A Tale of Two Missions: Exploring Mars' Enigmatic Aurora | It is now recognized that aurora are a regular feature of the Martian upper atmosphere, caused by the precipitation of charged particles from the near-space environment. They occur detectably to some degree somewhere on the nightside most of the time. Although known about since their discovery in 2005, our understanding of auroral location, variability, and dependence on solar wind conditions increased significantly with the MAVEN (Mars Atmosphere and Volatile EvolutioN) mission arriving in late 2014. MAVEN discovered three distinct types of ultraviolet aurora (diffuse, proton, and discrete), and has recorded more than 250 individual auroral detections. The arrival of the Emirates Mars Mission (EMM) in 2021, with its much higher sensitivity in the far ultraviolet and synoptic (i.e. near-full disk) perspective, is already revolutionizing our understanding of Martian Aurora. The number of individual pixel detections has increased more than 3 orders of magnitude, while a wide range of auroral morphologies has been discovered, with most comprising a new phenomenon known as Sinuous Aurora. The combination of auroral images from EMM with in situ plasma observations from MAVEN can help us start to understand the complex magnetospheric processes driving these enigmatic light shows on the night side of Mars. Lastly, I will preview ESCAPADE, the first UC Berkeley-led planetary mission, and how its unique multipoint plasma observations will further elucidate the highly dynamic coupled system of Mars' thermosphere, ionosphere, exospheric, and magnetosphere. | Anton Ermakov | |
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35 | 26-Apr | Andy Rivkin | remote | JHU/APL | The Double Asteroid Redirection Test: A Crash Course in Asteroid Defense | Asteroid impacts have profoundly shaped the history of life on Earth and have been implicated in at least one mass extinction event. Planetary defense is dedicated to predicting and preventing such disasters in the future. The Double Asteroid Redirection Test (DART) mission was launched in November 2021 and arrived at its target, the asteroid moonlet Dimorphos, on September 26, 2022. DART’s goals were to validate a planetary defense technique known as “kinetic impact”, which is changing an asteroid’s orbit by colliding a mass with it. Dr. Rivkin will present the motivation, operation, and initial results from the DART mission, including what we’ve learned from its spectacular final minutes and subsequent observations of Dimorphos and its parent body, the asteroid Didymos. | Ned Molter | |
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37 | 3-May | Rafael Fuentes | cancelled | CU Boulder | Convection in Giant Planets | Abstract | Burkhard Militzer | |
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39 | 10-May | Paul Dalba | in person | UC Santa Cruz | Discoveries of the Giant Outer Transiting Exoplanet Mass (GOT 'EM) Survey and New Insights into Giant Exoplanet Interior Structure | Years of in situ observations at Jupiter and Saturn have painted a complex picture of giant planet interior structure. Giant exoplanets present the opportunity to place these Solar System findings in a greater statistical context. However, the comparison is not straightforward because most well characterized giant exoplanets, those with measured mass and radius, are substantially hotter than Jupiter and Saturn. I will present results of a five-year observational effort focused on producing a novel sample of giant exoplanets on moderately long orbits (hundreds to a thousand days) with measured mass and radius. The temperatures of these giant exoplanets are far cooler than the typical hot Jupiter, well under 1000 K and below 300 K in some cases. Despite their long orbital periods, each of these exoplanets was initially discovered via the transit method by the Kepler or TESS missions. Our long-term Doppler spectroscopy campaigns, conducted at Keck and Lick Observatories, have finally yielded planet masses, which allow us to infer the bulk compositions of these cool giant exoplanets. I will discuss emerging empirical trends in the correlation between bulk metallicity and planet mass which may suggest that heavy element accretion is affected by the planetary orbital period. I will also present a few of the exoplanets individually as unique case studies and as opportunities for atmospheric characterization via JWST. This sample of giant exoplanets acts as a stepping stone that connects most hotter exoplanets to the cold gas giants of the Solar System. | Burkhard Militzer | |
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