List of Past Planetary Astronomy Lunches (PALS) : 01-Sep-2012 to 31-Dec-2012


Date:   Thursday 02-Aug-2012
Speaker:   Adam McKay (New Mexico State Univ.)
Title:  "[OI] in Comets"

H2O, CO2, and CO are typically the most abundant ices in cometary nuclei and are therefore considered the primary drivers of their activity. This makes knowledge of the abundances of these ices in comets important for understanding both cometary composition and sublimation behavior. H2O and CO can be observed directly from the ground, but CO2 is only observable from space. Therefore, finding an indirect ground-based measurement that can serve as a proxy for CO2 production is an important goal for studies of cometary composition. Observations of the forbidden lines of atomic oxygen can be employed as this proxy. The flux ratio of the 5577 Å line to the sum of the 6300 and 6364 Å lines (the oxygen line ratio) is considered indicative of whether the parent molecule of the atomic oxygen is H2O or CO2/CO. We present recent results from observations of comets C/2006 W3 Christensen, 103P/Hartley, and C/2009 P1 Garradd pertaining to the effectiveness of using the oxygen line ratio as a proxy for CO2 in comets.

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


Date:   Thursday 06-Sep-2012
Speaker:   No PALS This Week
Title:  No PALS This Week

No PALS This Week

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


Date:   Thursday 13-Sep-2012
Speaker:   Martin Elvis (Harvard-Smithsonian CfA)
Title:  Love, Fear and Greed: Why We Should Go to the Asteroids

Greed, fear, and love of knowledge send us to the asteroids. Most people fear asteroids as a threat to life on Earth. Scientists' love of knowledge drives them to check out the material our planet grew from, including the oceans, find clues to the origin of life and, maybe, find exotic materials we cannot make on Earth. And a few visionaries have long argued that the mineral wealth in the asteroids is huge. A single modest sized asteroid can contain enough platinum to rival Bill Gates' fortune, about $35 billion. And there are millions of asteroids out there. The time has now come where advanced space engineering and new astronomical knowledge can be combined to make exploring the asteroids possible, and potentially profitable. Martin Elvis will discuss how this can be done, making use of the International Space Station and the new NASA push to send humans to an asteroid.

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


Date:   Thursday 20-Sep-2012
Speaker:   Your Colleagues
Title:  Informal Open Discussion

There is no scheduled guest speaker for this week's PALS. We will instead have an open discussion on any planetary science related topics. If you would like to present a short something (10-20 min.), please contact Mike Kelley.

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


Date:   Thursday 27-Sep-2012
Speaker:   Alyssa Rhoden (GSFC)
Title:  Cracking under the stress: Europa's orbit, tides, and fracture systems

Europa's surface records a rich history of geologic activity including fracture systems driven by tidal stresses. These stresses are governed mainly by Europa's eccentric orbit but can also be influenced by obliquity, physical libration, and non-synchronous rotation. Hence, we can use observed fracture systems to constrain these rotational parameters. Using cycloids, strike-slip faults, and lineaments, I have been able to probe Europa's rotation state and the processes of fracture formation and modification. I will present the geologic case for obliquity and physical libration and discuss implications for non-synchronous rotation and polar wander. I will also present a model I developed for a fault’s response to tidal stress, which can reproduce observed strike-slip fault patterns on Europa.

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


Date:   Thursday 04-Oct-2012
Speaker:   Paul Bryans (GSFC)
Title:  Using Comets as a Solar Probe

Recently, two sungrazing comets have been observed as they passed through the solar corona. Both passages resulted in the significant enhancement of Extreme Ultraviolet (EUV) emission over a range of wavelengths. In this talk, I will explain this EUV emission by considering the evolution of the cometary atmosphere as it interacts with the ambient solar atmosphere. Understanding the EUV emission places constraints on the cometary composition and can provide valuable insight to the nature of the solar atmosphere. I will highlight some of the things we can learn about both the comet and the Sun from their interaction.

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


Date:   Thursday 11-Oct-2012
Speaker:   Various
Title:  "DPS Meeting Practice Talks"

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


Date:   Thursday 25-Oct-2012
Speaker:   Lucas Paganini (GSFC)
Title:  Lessons learned from detections of CO in two atypical comets

Recent results by NASA's DIXI and JAXA's Akari missions demonstrate that the carbon chemistry in comets remains incompletely understood. DIXI found that the outgassing in comet 103P/Hartley 2 was driven primarily by carbon dioxide (A'Hearn et al. 2011). The Akari survey of 18 comets revealed a significant abundance of CO2, but surprisingly it detected only upper limits for carbon monoxide in most comets comprising their sample (Ootsubo et al. 2012). Our recent ground-based observations showed a relatively large amount of CO in Oort cloud comet C/2009 P1 (Garradd), and also in the border-line Jupiter Family/Centaur comet 29P/Schwassmann-Wachmann 1. In this presentation, I will report these detections, compare them to existing studies, and explore possible links between chemical composition and cometary origins.

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


Date:   Thursday 01-Nov-2012
Speaker:   Ron Vervack (JHU APL)
Title:  Mercury's Exosphere: One Surprise After Another

Starting with the flybys and continuing into the orbital phase of the mission, Mercury's exosphere has presented us with a number of surprises related to the temporal and spatial distribution of species. Pre-orbit ideas about the sources and sinks of exospheric material are having to be reworked in light of the MESSENGER discoveries, and explanations for many of the observations are still incomplete or lacking entirely. I will review the MESSENGER observations of the exosphere and discuss the mysteries they have revealed.

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


Date:   Thursday 08-Nov-2012
Speaker:   Andy Rivkin (JHU APL)
Title:  Water, Hydroxl, and Ice in the Asteroid Belt

The asteroids are generally thought of as rocky or metallic bodies, with comets as their ice-rich distant relatives. Metoritical and spectroscopic evidence for OH-bearing minerals on asteroids dates back decades, however, and 2010 saw the first detection of ice (along with organic material) on an asteroidal surface. I will focus on our current understanding of the diversity of OH- and H2O-bearing asteroidal materials, and touch upon the dynamical and physical processes that have created and maintained that diversity over billions of years.

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


Date:   Thursday 15-Nov-2012
Speaker:   Dana Hurley (JHU APL)
Title:  Solar Wind Contribution to Volatiles on the Moon

We investigate the solar wind as a source of volatiles on the surface of the Moon. We simulate the interaction of the solar wind with the regolith and interpret the model results in terms of observables, both in the exosphere and on the surface.

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


Date:   Thursday 29-Nov-2012
Speaker:   Cristina Thomas, Goddard Space Flight Center
Title:  Spectral trends among near-Earth and small Main Belt asteroids

This talk will focus on two different topics in asteroid science. First, I will discuss the spectroscopic observing campaign designed to complement the ExploreNEOs Warm Spitzer Exploration Science program. ExploreNEOs was allocated 500 hours over two years (2009-2011) to determine the diameters and albedos for approximately 600 near-Earth objects using the Warm Spitzer capabilities of the Infrared Array Camera (IRAC). The combination of Spitzer derived albedos and diameters with spectroscopic data enhances our understanding of the near-Earth object population. Additionally, I will discuss space weathering in Main Belt asteroid families. Over time the space weathering process will increase spectral slopes and mute absorption features compared to fresh surfaces. These spectral trends were investigated using spectrophotometry within the Koronis and various other Main Belt families.

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


Date:   Thursday 06-Dec-2012
Speaker:   Michael DiSanti, Goddard Space Flight Center
Title:  The Volatile Composition of C/2009 P1 (Garradd): Evidence for an Oxygen-Rich Heritage?

Our campaign on long-period comet C/2009 P1 (Garradd) emphasized pre-perihelion observations using three world-class high-resolution IR (l ~ 2.8 – 4.7 um) spectrographs (with UT 2011 dates and Rh): Keck/NIRSPEC(Sep 09, 2.1AU; Oct 13, 1.8 AU), VLT/CRIRES (Aug 07, 2.4 AU; Sep 17-21, 2.0 AU), and NASA-IRTF/CSHELL (Sep 08, 2.1 AU) to measure nine parent volatiles (H2O, CO, CH4, C2H2, C2H6, HCN, H2CO, CH3OH, NH3). We also sampled its composition post-perihelion on one date (2012 Jan 08, 1.57 AU) with NIRSPEC, thereby providing a pre-/post-perihelion comparison of abundances.

Compared with the majority of Oort cloud comets, our observations of C/2009 P1 reveal highly enriched CO, severely depleted C2H2, normal C2H6, and normal to somewhat enriched CH3OH. I will present results of our observations and discuss possible implications for conditions experienced by its pre-cometary ices. I will also compare spatial distributions of H2O emission with those of other parent volatiles. H2O showed a pronounced pre-perihelion excess in the sunward-facing hemisphere that was not present for other profiles. Such comparisons will be used to estimate relative amounts of "native" and excess contributions to the total water production.

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


This page was automatically generated on: 13-Jan-2016.