List of Past Planetary Astronomy Lunches (PALS) : 01-Jan-2010 to 01-Jun-2010


Date:   Thu, 28-Jan-2010
Speaker:   Tyler Robinson (U. Washington)
Title:  EPOCH Observations of Earth

Abstract: The EPOXI Discovery Mission of Opportunity obtained spatially- and temporally-resolved visible photometric (0.3-1.0µm) and near-infrared spectroscopic (1.05-4.8µm) observations of Earth on three dates (3/19/08, 5/29/08 and 6/5/08). We have used the NASA Astrobiology Institute's Virtual Planetary Laboratory 3-D spectral Earth model to simulate these data and have matched visible, multi-wavelength 24-hr lightcurves of the Earth to within 3% at most wavelengths. To reproduce the observations we have run the model at a spatial resolution of over 12,000 pixels, an atmospheric resolution of 48 pixels and a cloud treatment with 6 categories of water clouds. Our updated model is capable of generating spatially- and temporally-resolved spectra of Earth, making it a useful tool for feasibility studies for future space-based planet detection mission (e.g., NASA TPF and ESA Darwin). The model also will be used to better understand sensitivity to global signatures of habitability and life in disk-integrated spectra of Earth. As an example of the application of this model to future extrasolar terrestrial planet observations we have used it to simulate the phase-dependent contribution of Earth's ocean "glint spot" to the total illuminated fraction. The "glint spot" is generated by specular reflection of sunlight on Earth's oceans and could potentially be used to detect oceans on extrasolar planets. Both clouds and oceans exhibit phase-dependent brightnesses, possibly obscuring the detection of, or eliminating the ocean glint.

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 04-Feb-2010
Speaker:   Lucy McFadden (UM)
Title:  Romancing the Asteroid in Sudan

Abstract: The near-Earth asteroid, 2008 TC3, was discovered by the automated Catalina Sky Survey Telescope on Oct. 6, 2008. Nineteen hours later it disintegrated at an altitude of 37 km over the Nubian desert in northern Sudan. The debris rained down in a strewn field that was found near train station No. 6 (Almahata Sitta in Arabic) a few months later. In early December of this year, the 4th and likely final scientific recovery expedition was lead by faculty and science students from the University of Khartoum retrieving more than 250 samples of a rare meteorite type called a polymict ureilite. I will discuss the scientific implications of this serendipitous asteroid sample return and share my personal experiences collaborating with scientists and students in the Sudan, the largest country in Africa and the Arab World.

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 11-Feb-2010
Speaker:   Laura Woodney (Cal State, San Bernardino)
Title:  Rotation of Comet Tuttle

Abstract: In the winter of 2007/2008 Comet 8P/Tuttle had its first good apparition since 1980. I will discuss using narrowband CCD images to determine the rotation period of the comet.

(Canceled due to snow.)

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 18-Feb-2010
Speaker:   Mike A'Hearn (UM)
Title:  The Threat of NEOs and the NRC Report

Abstract: Why are NEOs a threat to Earth? How big a threat are they? What is the state of the science - discovery, characterization, threat? Why did congress demand that the NRC carry out an assessment? What did the NRC say about how to address the threat?

I will summarize the above topics, including my own assessments of where the US and the world could and should go in dealing with the threat.

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 25-Feb-2010
Speaker:   LPSC practice talks
Title:  

Abstract:

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 04-Mar-2010
Speaker:   LPSC
Title:  no talk

Abstract:

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 11-Mar-2010
Speaker:   Evgenya Shkolnik (CIW-DTM)
Title:  Star-Planet Interactions: The Tidal and Magnetic Influence of Hot Jupiters

Abstract: The interacting processes taking place between a giant planet orbiting its star within 10 stellar radii (also known as a "hot Jupiter") have been getting increasing attention both observationally and theoretically. Our work has shown that such a short-period planet can induce activity on the upper atmosphere of its host star through both tidal and magnetic star-planet interactions (SPI).

Evidence for magnetic SPI includes a diverse array of photometric, spectroscopic and spectropolarimetric studies. Because of the small separation (< 0.1 AU), many of the hot Jupiters lie within the Alfven radius of their host stars, allowing direct magnetic interaction with the stellar surface. Models show both the stellar and planetary magnetic fields are strongly affected, possibly influencing the magnetic activity of both bodies, as well as modifying irradiation and non-thermal and dynamical processes.

In addition, a hot Jupiterís tidal influence on its star may increase the stellar rotation rate and thus also increase the global stellar activity level. Our recent work has shown that stars with hot Jupiters have twice the UV emission than stars with planets in wider orbits, which is also anti-correlated with the stellar synchronization time scales. Even though the stars with hot Jupiters are not fully synchronized (full synchronization in most cases will take longer than the age of the Universe), they have already undergone some increase in rotation rate, provided that the planets migrated early on in the system's history.

Studying both tidal and magnetic star-planet interactions aids our understanding of the formation, migration and evolution of hot Jupiters, and provides the best-available probe of exoplanetary magnetic fields.

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 18-Mar-2010
Speaker:   SPRING BREAK!! (Furlough day)
Title:  no talk

Abstract:

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 25-Mar-2010
Speaker:   Padi Boyd (GSFC)
Title:  Kepler: NASA's First Dedicated Exoplanet Space Mission

Abstract: NASAís Kepler mission was launched in March 2009 into an Earth-trailing heliocentric orbit, where it stares virtually continuously at a 100 square degree patch of sky monitoring more than 150,000 stars in the optical to search for planets. Kepler was specifically designed to be capable of detecting planets the size of Earth in Earthlike orbits around stars of similar age and size to the Sun. Kepler produces continuous, simultaneous, evenly sampled light curves with unprecedented photometric precision for its target stars. These are processed in parallel on the ground to search for events consistent with planetary transits. A rigorous procedure is followed for exoplanet candidates (those target stars which show a minimum of three regularly spaced transits with statistically equivalent depths), in which the Kepler data itself and ground-based follow-up imaging and radial velocity observations are collected and analyzed to rule out a variety of false positives and confirm true planets to a high degree of confidence. I will discuss the history and early science operations of the mission from my perspective as the NASA Headquarters Kepler program scientist. Iíll summarize the first year of science results, and discuss what might be expected in the year to come. Due to geometric reasons alone, the majority of Keplerís target stars will not produce transits, however the high quality continuous photometric data collected on these targets will allow unique variability studies to be performed on archival data. There is also an active guest observer program through which community members can add high scientific merit targets to the observing program. I will discuss the variety of ways in which science community members can get involved with Kepler data analysis.

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 01-Apr-2010
Speaker:   Carolyn Crow (UM)
Title:  Our Solar System at Low Spectral Resolution: A Starting Point for Characterizing Colors of Other Solar Systems

Abstract: Carolyn A. Crow (UM), L. A. McFadden (UM), T. Robinson (UW), T. A. Livengood (NCESSE), T. Hewagama (UM), R. K. Barry (GSFC), L. D. Deming (GSFC), V. Meadows (UW), C. M. Lisse (APL)

The first visible-light studies of Earth-sized planets around other stars will employ photometry or low-resolution spectroscopy to observe disk-integrated radiation from the unresolved planet. Analysis of he photometric properties of the planets with in our own solar system can serve as a baseline for characterizing future extrasolar planets observations. We have analyzed the spectral behavior of the Moon, Earth, and Mars through interference filters covering 350-950 nm using the High Resolution Instrument (HRI) on the Deep Impact spacecraft. Ground based full-disk observations of the other six solar system planets and Titan from McCord et al. 1972 and Karkoschka 1994 were also used in our analysis of the limitations of using photometric colors to characterize extrasolar planets. We also determined the optimal filters for characterizing planetary colors and distinguishing Earth-like planets.

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 08-Apr-2010
Speaker:   Jessica Sunshine (UM)
Title:  Hidden in Plain Site: The Discovery of Spinel-Rich Volcanic Deposits on the Near-Side of the Moon

Abstract: Investigation of spectral anomalies in global data acquired with the Moon Mineralogy Mapper (M3; M-cubed) has revealed a new, unique, and unexpected spinel-rich lithology on the central nearside. These spinel-rich deposits are found only among the Sinus Aestuum explosive volcanic deposits and are notably absent from other nearby pyroclastic units. While these deposits are spatially extensive (10000s km2), the most spinel-rich signatures occur at km-scales. M3's combination of high signal-to-noise, extended spectral range, and spatial resolution (140 m/pixel) has enabled this unique, previously hidden, spinel-rich deposit to be uncovered.

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 15-Apr-2010
Speaker:   Casey Lisse (JHUAPL)
Title:  Mid-IR Spectroscopy of Comets & Dusty Disks: Mineralogical and Elemental Clues to the Formation and Evolution of Solar Systems

Abstract: With observations made by the Spitzer Space Telescope, we are beginning to understand the details of how the composition and formation of our own Solar System compares to those of other stars in our Galaxy. This is a major question in astronomy, and recent, detailed observations by Spitzer of comets (remnants of the solar systems proto-planetary disk), proto-planetary disks around Young Stellar Objects, debris disks around moderate-age stars, and dust rich DZ white dwarfs have given us a collection of detailed spectra containing clues about our Galactic context. In this talk I will discuss Spitzer and related ISO mid-infrared (5 to 40 micron) spectroscopy of 6 comets and the dusty systems SST-LUP3-1, HD100546, HD163296, HD113766, HD172555, EF Cha, Eta Corv, HD69830, G29-38 and GD362. Using the results from the recent Deep Impact and STARDUST space missions as ground truth, we can now constrain the relative abundances of silicates, carbonates, water ice/gas, amorphous carbon, sulfides, and polycyclic aromatic hydrocarbons (PAHs) in dusty disks, and directly relate the temperature of the circumstellar dust to its location with respect to the system primary. I will discuss the similarities and differences in the spectra, the amount, kind, and location of the dust and gas species detected, the primitive or advanced state of processing of the dust, compositional solar system analogues for the inferred source parent bodies, and their implications for our Solar System's origin and evolution.

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 22-Apr-2010
Speaker:   Dan Pendick (GSFC)
Title:  Science as Storytelling: How to Weave a Gripping Tale from Your Research to Engage and Inform the Public

Abstract:

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 29-Apr-2010
Speaker:   Nathan Bridges (JHUAPL)
Title:  Aeolian Processes on Mars

Abstract: Aeolian (wind) processes are the most dominant geologic agents operating on Mars today. The movement and deposition of dust, and to a more limited extent, sand, occurs in the present environment. Because Mars has a very thin atmosphere, sand movement should be rare. However, orbital images show extensive dunes, ripples, and other sand deposits, and rocks investigated by the MER Opportunity rover show sandstone as a component in the ancient geologic column. In addition, most rocks on the surface appear to have been abraded by windblown sand. Therefore, wind activity on Mars in the past must have been greater than that of today, probably due to higher wind speeds or a more dense atmosphere. An overview of Martian aeolian geology and processes, and a discussion of these questions, will be presented in the talk.

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 06-May-2010
Speaker:   Soko Matsumura (UM)
Title:  Dynamically Unstable Planetary Systems Emerging out of Gas Disks

Abstract: To date, more than 400 extrasolar planets, and more than 40 multiple-planet systems have been discovered. Most of them are more massive than Neptune, and many have less than a 1 year orbital period. Some have eccentric, and/or inclined orbits, while others have circular, well-aligned orbits. Awaiting the future observations of Earth-like planets, it is of vital importance to understand the formation and evolution processes of these giant planetary systems. In this talk, I will describe our current understanding of the statistical properties of extrasolar planetary systems. N-body simulations of multiple-planet systems without gas disks successfully reproduce the observed eccentricity distribution of extrasolar planetary systems. However, such simulations cannot explain the observed semi-major axis distribution, when we assume that planets were formed beyond the ice-line. To explain the semi-major axis and eccentricity distributions simultaneously, we take account of gas disks' effects on evolution of planetary systems by utilizing a hybrid N-body and 1D gas disk code. The close-in planets with the orbital period of less than about 10 days (so-called "3-day pileup") may be well-explained by such simulations combined with the tidal evolution.

For further information please contact PALS coordinator Dr. Jian-Yang Li at jyli@astro.umd.edu, 301-405-2103.


Date:   Thu, 13-May-2010
Speaker:   Joe Carroll (Tether Applications, Inc.)
Title:  Cheaper by the dozen: small-body missions by solar-sailing nanosats

Abstract: The smaller the spacecraft and the further it travels from earth, the more the comm-link drives the overall spacecraft and mission design. In the limiting case, one might design a minimal deep-space comm-link, and then determine what must be added to it to allow a useful mission. Such a mission may not make sense, since it may require spending too much development funding to save too little launch mass at the margin. But if the goal is not one mission but many similar missions, for example to collect statistically meaningful data on NEOs and other small bodies, this approach could be very fruitful. This talk will discuss the implications of one such approach, using solar sails and laser-comm to enable dozens of university-run nanosat-class missions to small bodies.

For further information please contact PALS coordinator Dr. Sebastien Besse at sbesse@astro.umd.edu, 301-405-9922.


Date:   Thu, 17-June-2010
Speaker:   Nelly Mouawad (UM)
Title:  New Constraints on Mercury's Sodium Exosphere

Abstract:We have used observations of sodium emission obtained with the McMath-Pierce solar telescope and MESSENGER‚Äôs Mercury Atmospheric and Surface Composition Spectrometer (MASCS) to constrain models of Mercury‚Äôs sodium exosphere. The distribution of sodium in Mercury‚Äôs exosphere during the period January 12-15, 2008, was mapped using the McMath-Pierce solar telescope with the 5-Y‚Äė√ó5-Y¬° image slicer to observe the D-line emission. On January 14, 2008, the Ultraviolet and Visible Spectrometer (UVVS) channel on MASCS sampled the sodium in Mercury‚Äôs anti-sunward tail region. We find that the bound exosphere has an equivalent temperature of 900-1200 K, and that this temperature can be achieved if the sodium is ejected either by photon-stimulated desorption (PSD) with a 1200 K Maxwellian velocity distribution, or by thermal accommodation of a hotter source. We were not able to discriminate between two assumed velocity distributions of the ejected particles for the PSD but the velocity distributions require different values of the thermal accommodation coefficient and result in different upper limits on impact vaporization. We were able to place an upper limit on the impact vaporization source rate of 2.1√ó106 cm-2 s-1, which is six times the nominal source rate given by Killen et al. (2004). The variability of the week-long ground-based observations can be explained by variations in the sources, including both PSD and ion-enhanced PSD, as well as possible temporal enhancements in meteoroid vaporization. Knowledge of both dayside and antisunward tail morphologies and intensities are necessary to correctly deduce the exospheric source rates, processes, velocity distribution and surface interaction.

For further information please contact PALS coordinator Dr. Sebastien Besse at sbesse@astro.umd.edu, 301-405-9922.


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