CIPS Seminar Spring 2018 (public)
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CIPS SEMINARS - Spring 2018
131 Campbell Hall
Wednesdays 12:30-13:30 PM
17-JanCheng LiCalTech, NASA Postdoctoral Program Fellow The First Year of Juno Observing Jupiter’s atmosphereIt’s been more than a year since the Juno spacecraft arrived at Jupiter. The Juno Microwave Radiometer measured the Jovian tropospheric radiation from the north pole to the south pole. The JunoCAM pictured Jupiter’s polar clouds for the first time. On July 11th, 2017, the Juno spacecraft flow over the Great Red Spot, sensing its depth down to at least 200 bars. And, these are only part of the results that the Juno mission has revealed. In this talk, I will introduce Juno’s new discoveries of Jupiter’s atmosphere including the ammonia distribution, the polar vortices and the structure of the Great Red Spot. New spectral inversion techniques are developed and applied to invert the Juno Microwave Radiometer observations. Shallow water models are used to study the stability of the polar vortices. Order-of-magnitude calculations are performed to speculate the dynamics of the GRS. What we learned is a whole new Jupiter.Imke de Pater
24-JanMax Millar-BlanchaeJPL, Hubble FellowLeveraging Polarimetry to probe Exoplanet and Brown Dwarf AtmospheresWith the advent of second generation direct imaging instruments, such as the Gemini Planet Imager (GPI), we are now able to measure low resolution spectra of directly imaged exoplanets. The colors, absolute magnitudes and spectra of these planets show a remarkable similarity to those of free-floating brown dwarfs. Using atmospheric models, we are able to fit exoplanet spectra to obtain constraints on effective temperature, surface gravity, and put constraints on cloud properties. However, systematic offsets between exoplanet spectra and these models demonstrate that our knowledge of cloud properties remains incomplete. Spectropolarimetric measurements provides a promising venue to further probe cloud properties observationally, as the shape of the polarized spectra is determined by cloud properties. In this talk, I will describe a series of on-going efforts to leverage polarimetric measurements to learn more about cloud properties in brown dwarfs and directly imaged planets. These efforts include: advanced 2-D cloud coverage modeling; WIRC+Pol, a new spectropolarimetric upgrade at Palomar; and broadband observations using GPI and its European counterpart, SPHERE. These preliminary efforts set up both the technical and scientific background to eventually carry out spectropolarimetric measurements of directly imaged exoplanets, while at the same time providing empirical measurements to help refine atmospheric models applicable to both brown dwarfs and exoplanets. Paul Kalas
31-JanJack LissauerNASA Ames, Staff ScientistKepler's Multiple Planet SystemsMore than one-third of the 4700 planet candidates found by NASA’s Kepler spacecraft are associated with target stars that have more than one planet candidate, and such “multis” account for the vast majority of candidates that have been verified as true planets.The large number of multis tells us that flat multiplanet systems like our Solar System are common. Virtually all of the candidate planetary systems are stable, as tested by numerical integrations that assume a physically motivated mass-radius relationship. Statistical studies performed on these candidate systems reveal a great deal about the architecture of planetary systems, including the typical spacing of orbits and flatness. The characteristics of several of the most interesting confirmed Kepler & K2 multi-planet systems will also be discussed.Imke de Pater
7-FebRobert LillisSpace Sciences Lab, Associate Research Physicist MAVEN and the mysterious disappearance of Mars' atmosphereWhy is the surface of Mars no longer habitable? Sounds like a straightforward question, right? However, those nine words comprise one of the most vexing questions in planetary science. There is now overwhelming evidence from orbiters and rovers that Mars was once a place where liquid water flowed on the surface and, thus, life as we know it could have thrived, at least episodically. However, such stable surface water requires an atmospheric surface pressure much higher than today’s ~7 millibars (<1% of Earth’s pressure) to prevent evaporation and cause greenhouse warming. Where did this ancient atmosphere go? If it had all been absorbed back into the crust, abundant carbonate minerals should exist on or near the surface. However, extensive surveys from orbit have revealed not nearly enough carbonate to account for all the carbon dioxide that has been lost. The only other explanation: The atmosphere escaped out to space over billions of years. But how did this happen? What physical processes drove the escape? How did they vary over time as solar radiation and the solar wind buffeted Mars’ atmosphere, which lacked the protection of a global magnetic field? And, most importantly, how much total atmosphere escaped over Mars’ history? These are the questions that motivate the MAVEN team’s scientific efforts—day in and day out—as we analyze and interpret data from our nine science instruments. Our overarching strategy is to use MAVEN’s observations to understand the processes that cause atmosphere to escape out into space, as they operate under the conditions experienced by present-day Mars. We will then combine that with knowledge of how those conditions have varied over time to estimate the total loss of atmosphere. Sounds simple, right? But as always, and as you probably guessed, the devil is in the details. I will present an overview of scientific results from the first three years of the MAVEN mission to Mars, with an emphasis on atmospheric loss processes and how these have transformed the Martian climate over time.Michael Manga
14-FebChristina Hedges, Geert Barentsen, Michael Gully-Santiago, Ann-Marie CodyNASA AmesData products and science from NASA's K2/Kepler Guest Observer OfficeThis seminar will consist of a series of "lightning talks" lasting ~10 min each, with time for questions and discussion afterward. The speakers are all from NASA's K2/Kepler Guest Observer Office and will be sharing new data products and/or science that is relevant to CIPS.Megan Ansdell
21-FebAndrew PoppeSpace Sciences LabInterplanetary dust: the view from near and farInterplanetary dust is present throughout the solar system and provides a key connection to fundamental planetary building blocks. IDP grains are produced via several processes, including asteroidal disruption, cometary outgassing, and grain-grain mutual collisions and arise from several parent sources, such as the asteroid belt, Jupiter-family, Halley-type, and Oort Cloud comets, and Edgeworth-Kuiper Belt objects. The relative density and flux of IDPs from any individual source at a given location in the solar system is a complex function of both dust production rates and subsequent gravitational and non-gravitational interactions (i.e., radiation pressure, Poynting-Robertson drag, Lorentz force, etc.). We describe recent modeling and observational efforts directed at understanding and constraining both the individual components and overall morphology of the interplanetary dust cloud throughout the solar system. In particular, we touch on new results from the New Horizons Student Dust Counter and the Lunar Dust Experiment (LDEX) onboard the Lunar Atmosphere and Dust Environment Explorer (LADEE). We also briefly discuss two new mission concepts regarding interplanetary dust. The first, i2DUNE, would measure interplanetary and interstellar dust from an Earth-orbiting (or near-Earth) spacecraft making use of next-generation trajectory and mass composition dust detectors. The second, Interstellar Probe, is a mission to leave the Solar System in order to gain a unique vantage point for look-back imaging of the interplanetary dust complex. IP would provide global imaging of our solar system’s debris disk in analogy with the plethora of observations of exozodiacal disks around other stars. Both of these missions present exciting opportunities to revolutionize our view and understanding of dust both near and far.
Doug Hemingway
28-FebMegan AnsdellUC Berkeley Astronomy, CIPS Postdoc FellowProtoplanetary Disk Demographics with ALMA: Overview and UpdatesThe recent successes of large-scale exoplanet surveys have opened the field of exoplanet statistics, revolutionizing our view of the universe. We now know that planets are common around other stars, but also that exoplanets come in a variety of sizes, compositions, and orbital architectures that that often differ in striking ways from our own solar system. But how and why do such diverse exoplanet systems form? To answer these fundamental questions, we must understand the structure and evolution of the "protoplanetary disks" of gas and dust around young stars where planets form. To this end, we are conducting large-scale surveys of nearby star-forming regions with the Atacama Large Millimeter/sub-millimeter Array (ALMA), which is now offering orders of magnitude higher sensitivity and resolution over previous (sub-)mm facilities. I will give an overview of the recent ALMA protoplanetary disk surveys and their implications for disk evolution and planet formation as well as present the latest results from our survey of gas disk sizes and grain growth in the Lupus star-forming region. Paul Kalas
7-MarRobert CitronUC Berkeley EPSOceans on MarsPutative paleo-shorelines in the northern plains of Mars have been used as evidence of an early Martian ocean. However, the shorelines deviate in elevation from an equipotential (by up to several kilometers), which has been used to challenge the notion that they formed via (and the existence of) an early ocean. We show that long-wavelength variations in shoreline topography can be explained by deformation due to the emplacement of Tharsis, a volcanic province that dominates the gravity and topography of Mars. Our results imply that oceans on Mars formed early, and point to a close relationship between the evolution of oceans on Mars and Tharsis volcanism, with broad implications for the geology, hydrological cycle, and climate of early Mars.Paul Kalas
14-MarEric NielsenStanford, Research ScientistThe Gemini Planet Imager Exoplanet Survey: a Trend in Wide Separation Giant Planets Occurrence Rate with Stellar MassGPIES (The Gemini Planet Imager Exoplanet Survey) is an 600-star survey to detect and characterize giant planets between 5 and 100 AU orbiting young, nearby stars. GPI combines a high order adaptive optics systems, an apodized Lyot coronagraph, and an integral field spectrograph to reach contrasts of 15 magnitudes within 0.5" of the central star. I present an overview of the highlights from the survey, including the recovery of known planets and brown dwarfs around our target stars, and the discovery of 51 Eridani b, a 2 Jupiter mass planet orbiting 13 AU from its star, and characterization of its atmosphere and orbit since the discovery. I also present the cautionary tale of the putative giant planet HD 131399 Ab, where GPI observations found this object to in fact be a background star, and the lessons for planet imaging going forward. One of the key goals of GPIES is to directly measure the occurrence rate of wide-separation giant planets, and I present early results on this front based on an analysis of the first half of the survey. For the first time we are seeing a trend in occurrence rate with stellar mass, which has profound implications for how these planets form and evolve. Paul Kalas
21-Marno seminar (LPSC Meeting)
28-Marno seminar (spring recess)
4-AprDoug HemingwayUC Berkeley EPS, Miller FellowThe Color of the MoonAbstract: Space weathering alters the optical properties of exposed surfaces over time, complicating the interpretation of spectroscopic observations of airless bodies like asteroids, Mercury, and the Moon. Solar wind and micrometeoroids are likely the dominant agents of space weathering, but their relative contributions are not yet well understood. Here I will show that the color of the Moon varies systematically with latitude and that the characteristics of this latitudinal trend match those observed at ‘lunar swirls’, where magnetic fields alter local solar wind flux without affecting the flux of micrometeoroids. I will argue that reduced solar wind flux, which should occur both at swirls and toward higher latitudes, is the common mechanism behind these color variations. This result helps us quantify the distinct effects of solar wind and micrometeoroid weathering and could aid in interpreting the spectra of airless bodies throughout the Solar System.
11-Aprno seminar (CIPS Workshop)
18-AprKevin StevensonSpace Telescope Science InstituteA Story of Exoplanet Characterization: Connecting Results from Telescopes Past, Present, and Yet to ComeExoplanet characterization has made significant advances in the last decade and will continue to do so for the foreseeable future. From the early days of Spitzer and Hubble, to the pending launch of JWST and even future mission concepts still under consideration, revealing exoplanet atmospheres' climates, compositions, and thermal structures through the transit technique has arguably been the most prolific means to study worlds outside of our own system. I will discuss recent efforts to understand exoplanet atmospheres through a 660-hour Spitzer phase curve survey program that is targeting seven short-period extrasolar planets, a multi-cycle Spitzer program that is monitoring transit timing variations of a K2 system, and a preparatory HST program whose primary goal is to identify targets for the recently-approved transiting exoplanet community early release science program with JWST. I will conclude with an introduction to the Origins Space Telescope (one of four large mission concepts under consideration for the 2020 decadal survey) and a description of how OST can expand upon the legacy of missions past and present to study the climates of Earth-size worlds orbiting within the habitable zones of nearby M-dwarf stars.Jason Wang
25-AprPeter GaoUC Berkeley Astronomy, 51 Pegasi b Postdoctoral FellowUnderstanding Exoplanet Cloudiness Across Parameter Space The increasing number of exoplanet atmospheres that have been characterized via transmission and emission spectroscopy has allowed for statistical studies of the cloudiness of hot and warm exoplanets as a group. Such studies have shown an emerging pattern, suggesting that exoplanets become clearer with increasing equilibrium temperature, but the physical mechanism for this has not yet been elucidated. The high temperatures of these atmospheres lead to exotic condensates, such as salts, sulfides, rocks, and metals, the behaviors of which as cloud particles are not well understood. In this talk I will show how a cloud physics model can be used to estimate the cloudiness of exoplanets across a range of equilibrium temperatures, gravities, and metallicities, and reproduce the general pattern of cloudiness of exoplanets that have been so far characterized. In addition, I will show the importance of photochemical hazes and spatial inhomogeneities in cloud opacity to interpreting current and future observations. Megan Ansdell
2-MayRebecca Jensen-ClemUC Berkeley Astronomy, Miller FellowTBDTBDMegan Ansdell
9-MayTeresa SteinkeTBDTBD
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