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CIPS SEMINARS - Spring 2020
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131 Campbell Hall
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Wednesdays 1:10-2:00 PM
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DateSpeakerAffiliationTitleAbstractHost
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22-JanCourtney DressingUCBA Tale of Five Spacecraft: Studying Nearby Planets with Kepler, K2, TESS, JWST, and LUVOIRIn a series of vignettes, I will highlight recent and ongoing work led by members of my research group and the LUVOIR Science and Technology Definition Team. First, I'll discuss the mass measurement of a transiting planet with a relatively long orbital period (spacecraft: Kepler, lead: Andrew Mayo). Second, I'll present a method for constraining the orbital parameters of transiting planets with ambiguous orbital periods (spacecraft: K2, leads: Shishir & Shashank Dholakia, Andrew Mayo). Third, I'll review my ongoing work to use data from the NASA TESS mission to determine how the frequency of planets depends on stellar mass for the smallest stars and work by Steven Giacalone to estimate the reliability of TESS planet candidates. Fourth, I'll introduce a framework for prioritizing TESS planet candidates for subsequent studies of planetary atmospheres with JWST (lead: Charles Fortenbach). Finally, I'll summarize the exoplanet science case and capabilities of the Large UV/Optical/IR Surveyor, a mission concept for a large space-based observatory capable of detecting biosignatures and constraining the frequency of inhabited planets. Marta Bryan
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29-JanCheng LiUCBA tranquil Jovian weather layerJupiter's atmosphere seems relentless, with multiple zonal jets hurling at the speed of hundreds of meters per second, and with the incessant popping of storms, clouds and vortices. Generations of atmospheric scientists have been emphasizing the role of moist convection due to the condensation of water in forcing both the weather and the large-scale circulation of the atmosphere. A number of papers used "random storms" to parameterize moist convection as forcing of the atmospheric circulation. Indeed, with proper stirring, any shallow, rapidly spinning sphere of fluid will organize into multiple zonal jets, spaced at the Rhine scale. However, the most recent observation of Jupiter's atmosphere using the microwave radiometer onboard the Juno spacecraft contradicts what one would infer from the "stirring picture", that chemically inert tracers shall mix through the atmosphere. Juno observed that ammonia gas is significantly depleted down to several tens of bars, well below its condensation level. The observation puts doubts about the primary energy transfer mechanism in Jupiter's atmosphere. Here I demonstrate that primordial heat inside Jupiter is transported by gravity waves rather than convection to the tropopause where energy can radiate out. As a result, Jupiter's weather layer is stably stratified, probably down to hundreds of bars. This affects the value of the isentrope chosen to model Jupiter's interior when using the temperature measured at 1 bar pressure level.Peter Gao
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5-FebMalena RiceYaleJovian weather at depth: from dark to dawnJupiter represents a class of planets whose major composition is hydrogen and helium, with a few condensable species forming visible clouds high up. Jovian atmospheres typically feature multiple zonal jets at the speed of hundreds of meters per second, and incessant popping of small-scale storms and vortices. By employing an Earth-like general circulation model, multiple authors have declared success in modeling the Jovian atmosphere by producing zonal jets in the low latitudes and vortices in the high latitudes. However, the most recent observation of Jupiter's atmosphere at depth by the Juno spacecraft contradicts what one would infer from the standard picture, that chemically inert tracers shall mix through the troposphere. Juno observed that ammonia gas is significantly depleted down to several tens of bars, well below its condensation level. The observation casts doubts on whether we really understand the most basic principle of the general circulation of Jovian atmospheres. Answers to questions like “How does the internal heat transfer through the atmosphere?”, “What is the entropy of Jupiter’s interior” become more obscure than before. Here I demonstrate that primordial heat inside Jupiter should be transported by gravity waves rather than convection to the tropopause where energy can radiate out. As a result, Jupiter's weather layer is stably stratified as opposed to neutrally stratified, probably down to hundreds of bars. This affects the value of the isentrope chosen to model Jupiter's interior when using the temperature measured at 1 bar pressure level.Paul Kalas
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12-FebJoshua Krissansen-TottonUCSCThe search for life elsewhere: Leveraging Earth system science approaches to anticipate exoplanet biosignatures and habitabilityUpcoming space- and ground-based telescopes will be capable of detecting biosignature gases in exoplanet atmospheres. However, distinguishing genuine signs of life from abiotic processes that may mimic inhabited planets will be challenging. Fortunately, Earth and the Solar System planets are invaluable natural laboratories for understanding biosignatures and planetary habitability more broadly. The early Earth provides examples of novel biosignatures, such as atmospheric disequilibrium between carbon-bearing species, which are potentially detectable with upcoming telescopes like JWST. Moreover, quantitative models of the geochemical evolution of planetary atmospheres and interiors that are validated using solar system planets will enable predictions about exoplanet habitability. For example, carbon cycle models developed to explain Earth’s climate evolution can be applied to formulate testable hypotheses for the habitable zone. Taken as a whole, these quantitative approaches to biosignature assessment will lay the groundwork for systematic searches for life elsewhere with next generation telescopes.Peter Gao
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19-FebAlex BrykBerkeleyCuriosity’s encounter with the Greenheugh pediment: What record will the landforms at the base of Mt.Sharp reveal about Mars climate history?Curiosity’s continued traverse across Glen Torridon and up Mt. Sharp will bring it in contact with landforms whose exposed stratigraphy likely records major environmental changes in the history of Gale Crater. Rocks exposed as the Greenheugh pediment comprise a nearly 3 square km erosionally-resistant planar sloping surface, the base of which truncates the strata of lower Mount Sharp. Curiosity’s close inspection of the exposed pediment walls may resolve whether the erosional truncation of the Mt. Sharp strata and subsequent deposit of the capping unit were driven by fluvial processes (as is commonly the case on Earth) or by wind (or both), providing key information of the processes and possible climate this landform and deposit record.Sean Wahl
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26-FebXinting YuUCSCIntegrating Materials Science Techniques into the Study of Planetary HazesPhotochemically produced hazes are prevalent in the atmospheres of planetary bodies in the solar system and could also be ubiquitous in exoplanetary atmospheres. Haze has been shown to affect the thermal structure and dynamics of planetary and exoplanetary atmospheres. It could also be a source of the surface material on planetary bodies and will therefore be involved in various surface processes. However, many physical and chemical processes involving the haze are unknown due to the lack of knowledge of the haze as a material. Because of its chemical complexity, many of the intrinsic properties of the haze are highly material dependent and currently have large uncertainties in models. We have been using material characterization techniques such as atomic force microscopy, contact angle analysis, and nanoindentation, to experimentally determine the material properties of planetary and exoplanetary haze analog materials. We measured material properties such as surface energy, mechanical properties, and electrostatic properties to understand not only the structures and behaviors of haze materials, but this information could also shed light on their formation, evolution, interaction with clouds and surface liquids, and their impact on the current and upcoming observations.Peter Gao
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4-MarSteph SallumUCSCImaging Protoplanets with Adaptive Optics and InterferometryObservations of mature planetary systems and protoplanetary disks have informed our understanding of planet formation, placing general constraints on its timescale and conditions. Despite a wealth of data, many open questions remain regarding how planets accrete and interact with their natal environments. Addressing these questions requires direct observations of forming planets themselves. Compared to mature planets, protoplanets are expected to have low infrared contrasts relative to their host stars. However, nearby star forming regions lie at much greater distances than typical directly-imaged planets. Protoplanets on orbits of several AU will be at or within the infrared diffraction limit of 8-meter class telescopes, necessitating novel imaging methods for direct detection and characterization. Interferometric techniques such as non-redundant masking (NRM), which turns a conventional telescope into an interferometric array, are well suited for protoplanet imaging. I will present the results of NRM protoplanet searches in transition disks - protoplanetary disks with inner clearings that may be shaped by forming planets. I will also describe the related kernel phase technique, which will enable simultaneous detection and characterization when applied on integral field spectrographs. Lastly, I will discuss prospects for direct protoplanet observations on the next generation of space- and ground-based facilities. Marta Bryan
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11-MarAnna ButterworthUBC - SSLLaboratory analyses of three (probable) contemporary interstellar dust particlesI will present results of synchrotron x-ray absorption spectroscopy measurements on three probable interstellar particles collected by the NASA Stardust Mission. These dust particles were collected in the Stardust Interstellar Dust aerogel collector, which was deployed and oriented toward the interstellar dust stream, and returned to Earth in 2006. A distributed citizen science search effort “Stardust@Home” found dozens of impact tracks in the aerogel. Three ~1µm diameter particles were not like the rest. They show some similarities — and differences -- to astronomical observations of interstellar dust. Burkhard Militzer
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18-Marno seminar(week of LPSC but we will have a seminar)
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25-MarSpring break
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1-AprCancelled / OpenUCSCTBDTBDMarta Bryan
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8-AprCancelled / OpenTBDTBD
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15-AprCancelled / OpenTBDTBD
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22-AprCancelled / OpenAmesTBDTBD
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29-AprCancelled / OpenUCBTBDTBD
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6-MayPeter GaoUCBA Unified Picture of Exoplanet Cloudiness Aerosols are common in the atmospheres of exoplanets across a wide swath of temperatures, masses, and ages. These aerosols strongly impact observations of transmitted, reflected, and emitted light from exoplanets, obfuscating our understanding of exoplanet thermal structure and composition. A variety of substances have been proposed for the makeup of exoplanet aerosols, including metal oxides and sulfides, elemental iron, chromium, and sulphur, and hydrocarbons; knowing the dominant aerosol composition would facilitate interpretations of exoplanet observations and theoretical understanding of their atmospheres. In this talk, I show that exoplanet aerosols are dominated by silicates and hydrocarbons. By constraining an aerosol microphysics model with trends in exoplanet transmission spectra, we find that silicates dominate aerosol opacity above planetary equilibrium temperatures of 950 K due to low nucleation energy barriers and high elemental abundances, while hydrocarbon aerosols dominate below 950 K due to a rapid increase in methane abundance and photodissociation rate. I also show that the dominance of silicate clouds can explain the observed homogeneity in the nightside temperatures of hot Jupiters by tying the brightness temperature to the silicate condensation temperature. This unified picture of exoplanet cloudiness can be tested by mid-infrared observations of silicate features that will be possible with the James Webb Space Telescope.
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13-MayReading Week
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