LPI Seminar Series
LPI seminars are held on most Fridays from 3:00–4:00 p.m. in the Lecture Hall at USRA, 3600 Bay Area Boulevard, Houston, Texas. Refreshments are served at 4:00 p.m. For more information, please contact Justin Filiberto (phone: 281-486-2118; e-mail: filiberto@lpi.usra.edu) or Michelle Kirchoff (phone: 281- 486-2116; e-mail: kirchoff@lpi.usra.edu). A map of the Clear Lake area (PDF format) is available here. The Acrobat Reader 8.0 is available from Adobe. This schedule is subject to revision.
See also the Rice University Department of Physics and Astronomy Colloquia and the Department of Earth Science Colloquia pages for other space science talks in the Houston area.
December 2008
- Friday, December 5, 2008 - Lecture Hall, 3:00 PM
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Jisun Park, NASA JSC
39Ar-40Ar age dating of Martian shergottites and nakhlites and its significance for age dating with the Mars Science Laboratory (MSL).Among all seven nakhlites five have been dated by 39Ar-40Ar at NASA-JSC. The ages of all the nakhlites are similar at ~1.2-1.4 Ga. Also, an isochron of total 40Ar versus total K for six nakhlites gives an age of 1325±18 Ma suggesting a common formation age for nakhlites. Unlike nakhlites, Ar-Ar ages of shergottites are strongly affected by excess 40Ar through all gas extractions and show older radiometric ages by other techniques. For example, Zagami contains excess 40Ar relative to its formation age of ~170 Ma as determined by the Sm-Nd method. 39Ar-40Ar analyses of separated plagioclase and pyroxene samples have been investigated to understand the origin of this excess 40Ar. All the separated martian samples show similar concentrations of excess 40Ar, ~1x10-6 cm3STP/g. Bulk and mineral separated samples of other shergottites also give concentrations of excess 40Ar ~1-2x10-6 cm3 STP/g, in spite of a variation in K content. This excess 40Ar was inherited from the shergottites’ magma, either by degassing of a larger volume of material or by early assimilation of old K-rich crustal material.
January 2009
- Thursday, January 29, 2009 - Lecture Hall, 3:00 PM
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John F. Mustard, Brown University
Hydrated minerals on Mars and their geologic environments: Implications for the history of waterPhyllosilicate and sulfate hydrated minerals were first definitively identified on Mars from orbit by the OMEGA (Observatoire pour la Mineralogie, L'Eau, les Glaces et l'Activitié) instrument on board Mars Express. Global mapping showed that sheet silicates are widespread but largely found in terrains of Noachian age while sulfates were localized in the region of Valles Marineris, Aram Chaos, Meridiani, and dunes in the northern plains. In contrast to sulfates, phyllosilicate formation requires moderate to high pH and high water activity. A major hypothesis evolving from this discovery is that the conditions necessary for phyllosilicate formation were specific to the Noachian, the earliest era in Mars' history and sulfate formation evolved subsequent to that as Mars experienced massive global change. I will explore this hypothesis incorporating new high spatial resolution, precision pointing, and nested observations by the Context Imager (CTX), Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), and the High Resolution Imaging Sci-ence Experiment (HiRISE)) on the Mars Reconnaissance Orbiter (MRO). These data provide enhanced capabilities to analyze surface mineralogy across the planet and determine the nature and geologic setting of hydrated mineral deposits. Analysis of the diversity of phyllosilicates, associated hydrated minerals, and their geologic setting based on integrated OMEGA-CRISM-MRO analysis will be covered and the implications considered.
