List of Past Planetary Astronomy Lunches (PALS) : 01-Jan-2013 to 01-Jun-2013


Date:   Thursday 17-Jan-2013
Speaker:   Han Li, National Astronomical Observatories, Chinese Academy of Sciences
Title:  China's Chang'e Mission and Chang'e 2 Flyby of asteroid Toutatis

China's first lunar spacecraft, Chang'e 1 (CE-1), was launched on October 24, 2007, axnd impacted the Moon on March 1, 2009 after a 16-month orbital mission. Following the success of CE-1, Chang'e 2 (CE-2) was launched on October 1, 2010 as a forerunner satellite of the future landing and rover mission. After completing its nominal mission, CE-2 reached the Earth–Sun L2 Lagrangian point on September 1, 2011, and flew by asteroid 4179 Toutatis on December 13, 2012. In this talk I will give a brief introduction of China's Lunar Exploration Program, the scientific results of CE-1 and CE-2, and present recent image data acquired by CE-2 as it flew by Toutatis.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 31-Jan-2013
Speaker:   Matthew Knight, Lowell Observatory
Title:  Near Sun comets observed by SOHO and STEREO... and Comet ISON

Solar and Heliospheric Observatory (SOHO) has discovered more than 2300 small comets in "sungrazing" orbits since launching in late 1995. Since 2006 it has been joined by the twin Solar Terrestrial Relations Observatory (STEREO) spacecraft, providing an unprecedented view of many of these comets from three vantage points simultaneously. I will discuss the insights gained by studying sungrazing comets and the exciting new observations made possible by recent advances in Sun-observing capabilities. I will also discuss the upcoming sungrazing Comet ISON (C/2012 S1) and consider its potential to live up to the "Comet of the Century" hype it is receiving.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 07-Feb-2013
Speaker:   Boncho Bonev (Goddard Space Flight Center)
Title:  Water Release in Comet 103P/Hartley 2: Distributions of Column Density, Rotational Temperature, and Ortho-Para Ratio

Long-slit spectroscopy can probe the inner comae of comets via spectrally and spatially resolved measurements. This capability strengthens the quantitative view of conditions within the closest 200 km from the cometary nucleus, thereby providing direct constraints for models of density and temperature distributions in this collisionally dominated region of the coma. The near-Earth approach of comet 103P/Hartley 2 in 2010 presented an especially interesting opportunity to investigate the near-nucleus region of an active comet. This talk will present spatially resolved measurements of rotational temperature, column density, and ortho-to-para ration and discuss insights into the nature of volatile release.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 14-Feb-2013
Speaker:   Michael Efroimsky and Valeri Makarov (USNO)
Title:  Bodily tides and spin-orbit resonances. Applications to Mercury, the Moon, and exoplanet Gliese 581d.

Tidal torques play a key role in rotational dynamics of celestial bodies. They govern these bodies’ tidal despinning, and also participate in the subtle process of entrapment of these bodies into spin-orbit resonances. This makes tidal torques directly relevant to the studies of habitability of planets and their moons.

Our talk will start with an explanation of how friction and lagging should be built into the theory of bodily tides. Then we shall dwell on several practical applications of the theory. These will include Mercury, the Moon, and super-earth Gliese 581d which now regarded as one of the main candidates for habitability.

Time permitting, we shall also address some popular fallacies. For example, contrary to what some books say, terrestrial planets and moons cannot be trapped into the so-called pseudosynchronous spin states. Exact spin-orbital resonances are the only stable states for such objects.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 21-Feb-2013
Speaker:   Ludmilla Kolokolova (UMD)
Title:  Why Polarimetry? - What we can learn about cosmic dust and planetary aerosols using polarimetry

Polarimetry is still an underestimated astronomical tool, although it can provide information that cannot be achieved by using any other means. Especially powerful it is in studying cosmic dust of all types (cometary, interplanetary, interstellar, dust in circumstellar disks and molecular clouds) and planetary aerosols (including those in atmospheres of exoplanets). I will briefly review new developments in polarimetric techniques, both instrumental and theoretical, and recent results in studying of cosmic, specifically cometary and debris disk, dust and (exo)planetary aerosols. I will also discuss polarimetric techniques suggested for search of biological and prebiological organics in space.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 28-Feb-2013
Speaker:   To be announced
Title:  To be announced

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 07-Mar-2013
Speaker:   Christina Viviano (APL)
Title:  Characterizing clay distribution, abundance, and origin on the Martian surface

Phyllosilicates (or clay minerals) are hydrated minerals formed in the presence of liquid water. On Earth, their formation is often indicative of a neutral, water-rich environment, capable of supporting and preserving organic matter. However, different phyllosilicate species may be produced in different pH levels, and water-to-rock ratios. The identification of mineralogically diverse phyllosilicates in small, localized deposits on Mars provides a complex record of their formation processes. While discrete outcrops of phyllosilicates have been previously identified in high-resolution visible/near-infrared hyperspectral images of Mars, regional coverage of these dataset at better resolution is limited. To better understand the geologic context of these deposits, I used the global coverage of the THEMIS thermal infrared multispectral imaging instrument to develop a technique for mapping new phyllosilicate deposits on Mars.

Phyllosilicate-bearing material across the surface of Mars appears to have formed in variable environmental settings. In some locations, phyllosilicates are associated with metamorphic assemblages and may be associated with a talc-bearing phase. This phase is found to be associated with magnesium carbonate and olivine bearing assemblages. We hypothesize this relationship and the limited occurrence of serpentine associated with these units indicates carbonation of serpentine was a localized process in this region. If this carbonation reaction was a widespread phenomenon in other ultramafic protoliths on Mars, it may have been an important process in the ancient Martian carbon cycle and could have provided a sink for CO2 in the past.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 14-Mar-2013
Speaker:   Your Pals
Title:  LPSC and other short talks

Your pals from UMD will give practice talks for the Lunar and Planetary Science Conference, as well as other LPSC-style talks to round out the hour.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 28-Mar-2013
Speaker:   Adeline Gicquel (GSFC)
Title:  Properties of water ice, dust and gas in comets: Results for Deep Impact and Implications for Rosetta

Comets contain the most primitive icy material remaining from the epoch of the Solar System's formation. Their composition may potentially be unchanged since their accretion in the protoplanetary disk. Studying them informs us about the physical and chemical processes of planet formation. When comets approach the Sun, an atmosphere, called the coma, consisting of dust and products of ice sublimation, surrounds their nuclei.

NASA's Deep Impact mission is the only mission to have examined material from the interior of a comet nucleus resulting from a planned collision that occurred on July 4th, 2005. I will present the work I have done on the ejecta created by this event, which allowed me to: 1) analyze the activity of Comet 9P/Tempel 1 and the properties of its coma before and after the impact, and 2) determine the dust-to-ice ratio in the deep layers of the nucleus. To perform this research, I developed numerical models to interpret infrared spectroscopic data from the Spitzer Space Telescope before and after impact.

The ESA (European Space Agency) Rosetta spacecraft was launched in 2004, and will reach comet 67P in May 2014. The lander, Philae, will land on the nucleus in 2014, and the orbiter will be maintained in the vicinity of the comet until 2015. I will show the work that I have done on the icy-grain sublimation and the detectability of dust with MIRO, VIRTIS, and OSIRIS onboard Rosetta to prepare the science activity plan. The synthetic spectra for comet 67P/Churyumov-Gerasimenko are obtained for heliocentric distances between 3.5 AU to 1.3 AU. The computations are made for different geometries of observations and physical properties of the grains to estimate the detectability of dust.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 04-Apr-2013
Speaker:   Doug Hamilton (UMD)
Title:  There's a Giant Invisible Ring around Saturn!

Saturn's diffuse outer Phoebe Ring is an immense structure spanning over 30 million km (500 Saturn radii) and dwarfing all other known rings. The ring was discovered by Spitzer infrared imaging in 2009 and was recovered by the WISE spacecraft in 2011. The WISE images are the first to show the full extent of the ring and they are detailed enough to allow dynamical modeling to be used to constrain particle properties. Dusty ring particles are created by impacts onto Phoebe and other distant satellites, their orbits are altered rapidly by radiation pressure and more slowly by Poynting-Robertson Drag, and most of this material finally finds its way to the dark side of Iapetus. We model these processes numerically and build up synthetic ring profiles, making different assumptions about the unknown particle size distribution. We create synthetic ring profiles to compare to the data and rule out many common distributions. For instance, we find that the WISE data cannot be fit by a simple power law particle size distribution as is typically assumed for rings. Instead, the majority of the flux in the outer parts of the ring must be due to an excess of particles with sizes larger than several centimeters. In addition, we argue that the small grains have higher temperatures than large ones which significantly augment their infrared signatures.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 11-Apr-2013
Speaker:   Olivier Groussin (Lab. d'Astrophysique de Marseille)
Title:  D/H ratio in the Solar System: a review for non experts

*** Special time this week only! 11:00 ***

D/H ratio is a probe to constrain the origin and evolution of all solar system objects, from small bodies to giant planets. I will present the different values of D/H for solar system planets, small bodies and meteorites, and present our current understanding for the large range of D/H values. This is a review talk.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 18-Apr-2013
Speaker:   Neil Dello Russo (APL)
Title:  Strengths and Limitations of High-Resolution Infrared Spectroscopy Revealed Through the Study of Comets 73P/Schwassmann-Wachmann 3 and 103P/Hartley 2

The recent apparitions 73P/Schwassmann-Wachmann 3 and 103P/Hartley 2 were each exceptional in their own way. Both were highly active Jupiter-family comets that made close approaches to the Earth. 73P/SW3 was breaking into pieces, allowing the study of different fragments from the same parent body. Ground-based observations of 103P/Hartley 2 had the rare context of in-situ spacecraft observations from the NASA EPOXI Mission. Results from high-resolution ground-based infrared studies of these comets will be discussed including insights gained and reinforced about the strengths and limitations of this technique.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 25-Apr-2013
Speaker:   Noah Petro (GSFC)
Title:  Hydration Associated with Silicic Volcanism on the Moon: Deep Internal Water On the Surface?

Recent data from multiple instruments and missions orbiting the Moon have shed light on a unique style of lunar volcanism. These silica-rich volcanic features are distributed across the nearside in association with other, common, lunar volcanic features. However, on the lunar far side, there are two small unusual volcanic features far from other forms of volcanism. In both cases there appears to be an enhancement in hydroxyls associated with the volcanic features. The geology and the distribution of hydroxyls at these unusual far side features will be discussed.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 02-May-2013
Speaker:   Erin Ryan, GSFC
Title:  New Views of the Asteroids from Mid-IR Surveys

Although well over half a million asteroids are known in our solar system, only ~2000 asteroids had known diameters, albedos and compositional types at the turn of the century. Within the last 5 years, surveys in the mid-infrared by the Spitzer Space Telescope and the WISE mission have increased the number of asteroids with diameters and albedos by more than a factor of two. I will present results from Spitzer surveys and some new analysis of asteroid dynamical families utilizing IRAS, Spitzer and WISE mid-IR data in conjunction with optical Sloan Digital Sky Survey data.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 09-May-2013
Speaker:   Arielle Moullet (NRAO)
Title:  Exploring the physical and chemical diversity in the Solar System: the (sub)millimeter approach

The capabilities of the new ground-based (sub)millimeter facilities now put this technique at the forefront of solar system exploration, as they allow to retrieve unique physical and chemical properties that are essential to fully characterize the individual bodies, to identify processes acting on atmospheres and surfaces, as well as to derive clues pertaining to the formation and evolution of the solar system at large.

Observations of the surface thermal continuum emission from rocky planets and small bodies are indicative of the surface and subsurface brightness temperature field, that can be modeled to derive surface properties including albedo, roughness (related to soil porosity) and thermal inertia. In addition, the combined analysis of thermal and optical observations through the radiometric method allows to determine the equivalent size of small, spatially unresolved bodies. Amongst molecules that are often present as minor components in planetary atmospheres, several display strong (sub)millimeter rotational lines (CO, HCN, HDO, SO2,...) formed at altitudes above a few hundreds millibars. Modeling of the lines' profiles allows us to derive the temperature and molecular abundance vertical profiles in atmospheric regions that are rarely probed by other techniques. When a sufficient spatial resolution is reached, the combined retrieval of temperature, wind (through Doppler-shift mapping) and composition horizontal fields is a powerful tool to constrain the global atmospheric structure, and to identify seasonal and diurnal cycles.

In this talk, I will provide an overview of the possibilities offered by (sub)mm observations for the field of solar system science in the context of the deployment of ALMA. I will focus on a few topics illustrating the diversity of science cases that can be addressed: the chemical characterization of the tenuous atmosphere of Jupiter's volcanic moon Io, the mapping of minor species' in Neptune's atmosphere, the determination of the atmospheric wind regimes in Venus' middle atmosphere, and the retrieval of the size distribution in the Kuiper Belt.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


Date:   Thursday 06-Jun-2013
Speaker:   Christine Chen (STScI)
Title:  The Spitzer IRS Debris Disk Catalog

We have been carrying out a comprehensive study of unresolved debris disks observed using the Spitzer IRS. We found ~520 IRS spectra of debris disks in the Spitzer Archive that were observed from a heterogeneous set of Guaranteed Time Observer, Legacy, and General Observer Programs. The sources in these programs are typically nearby (at distances < 200 pc), possess a wide range of spectral types (typically B9 - K5, corresponding to estimated masses 0.5 - 5.5 Msun), and are evenly divided into three logarithmic age bins. We fit the IRS and MIPS 70 micron data, where available, with one and two temperature blackbody components, assuming grain temperatures of 30 - 500 K. We determine whether the data are more consistent with a one or two temperature blackbody model by estimating the mean likelihood for each model over its parameter space grid. For each target, we select the model with the higher mean likelihood. We discuss broad demographic trends in dust properties as a function of stellar properties and plan to publicly release our calibrated, photosphere-subtracted data to encourage use of the IRS data in all debris disk analyses.

For further information contact PALS coordinator Dr. Michael Kelley at msk@astro.umd.edu or 301-405-3796.


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