LPI Seminar Series

Effective January 1, 2009, LPI seminars will be held on Thursdays.

LPI seminars are held 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 Axel Wittmann (phone: 281-486-2105; e-mail: wittmann@lpi.usra.edu) or Jeremie Lasue (phone: 281-486-2195; e-mail: lasue@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 2009

Thursday, December 3, 2009 - Lecture Hall, 3:00 PM

John Grant, Smithsonian Institution
Selecting the Landing Site for the 2011 Mars Science Laboratory

The process for selecting the landing site for the 2011 Mars Science Laboratory began in late 2005 and has involved consideration of more than 50 candidate landing sites. Early landing site activities included definition and refinement of mission science objectives and engineering constraints on landing and mobility that have influenced the latitude, elevation, and relief of terrain upon which MSL will target and can land upon. The primary scientific goal of the Mars Science Laboratory (MSL) is to assess the present and past habitability of the Martian environments accessed by the mission. Habitability is defined as the potential of an environment to support life, as we know it. Such assessments require integration of a wide variety of chemical, physical, and geological observations. In particular, MSL will assess the biological potential of the regions accessed, characterize their geology and geochemistry at all appropriate spatial scales, investigate planetary processes that influence habitability, including the role of water, and characterize the broad spectrum of surface radiation. To enable these investigations, MSL will carry a diverse payload capable of making environmental measurements, remotely sensing the landscape around the rover, performing in situ analyses of rocks and soils, and acquiring, processing, and ingesting samples of rocks and soils into onboard laboratory instruments. Highly ranked candidate landing sites contain evidence suggestive of a past or present habitable environment and . are expected to preserve geological, chemical, and/or biological evidence for habitability that should be accessible to, and interpretable by the MSL investigations. The science community has been involved in every step of the site selection process and has suggested many of the candidate sites under consideration and participated in their evaluation at a series of open workshops. The top candidate landing sites for MSL will be discussed relative to how they might achieve these mission science goals. The process for considering new candidate sites and the timeline for selection of the final landing site will also be presented.

Friday, December 11, 2009 - Lecture Hall, 3:00 PM

Youxue Zhang, The University of Michigan
Bubble growth and degassing of lunar basalts

Although Moon is usually said to be "volatile-free", lunar basalts are often vesicular with mm-size bubbles. The vesicular nature of many lunar basalts suggests that they contain some initial gas content. A recent publication by Saal et al. (2008) estimated volatile concentrations in lunar basalts (though the estimate has been changing with time; personal communications with Saal). We model the growth of bubbles in lunar basalts using available surface tension, solubility, viscosity and diffusivity data and examining the role of various parameters. We also show a need for experimental determination of critical parameters relevant to lunar basaltic melts. Because lunar atmospheric pressure is essentially zero, the confining pressure on bubbles is supplied by surface tension and the overlying melt column. For a bubble with a diameter of 1 mm, the surface tension pressure is about 1200 Pa. Hence, by investigating bubble size, it is possible to estimate the minimum partial pressure of gases. A melt column of 0.2 m would provide a pressure of about 1000 Pa. Due to low volatile concentrations in lunar basaltic melt, bubbles only form at a shallow depth in the melt. Hence, vesicular lunar basalts must have formed at very shallow depth. Due to low volatile concentrations in lunar basalt, bubble nucleation is expected to be extremely difficult. Efficient nucleation sites must be available for bubble growth. Some findings from the modeling include: (a) Due to low confining pressure as well as low viscosity, even though volatile concentration is very low, bubble growth rate is extremely high, much higher than typical bubble growth rate in terrestrial melts. Hence mm-size bubbles can easily form once a bubble nucleates. (b) Because the pertinent pressures are low, pressure due to surface tension often plays a main role in lunar bubble growth, contrary to terrestrial cases. (c) Time scale to reach equilibrium bubble size increases as the confining pressure increases.

January 2010

Thursday, January 14, 2010 - Lecture Hall, 3:00 PM

Ella Sciamma O'Brien, LATMOS
TBA

Thursday, January 21, 2010 - Lecture Hall, 3:00 PM

David Jewitt, UCLA
TBA

Thursday, January 28, 2010 - Lecture Hall, 3:00 PM

Ryan Ogliore, Univ. of California, Berkeley
TBA

February 2010

Thursday, February 11, 2010 - Lecture Hall, 3:00 PM

Jim Kasting, Penn State
TBA

Thursday, February 18, 2010 - Lecture Hall, 3:00 PM

Ulrich Riller, School of Geography and Earth Sciences and Origins Institute, McMaster University, Hamilton, Canada
Origin of pseudotachylite in terrestrial impact basins

Pseudotachylite bodies in impact structures are dike-like and consist of angular and rounded wall-rock fragments enveloped by a microcrystalline and sporadically glassy matrix that crystallized from a melt. Knowledge of the formation of pseudotachylite bodies is important for understanding mechanics of complex crater formation. Most current hypotheses of pseudotachylite formation inherently assume that fragmentation and melt generation occur during a single process, either by (1) shock loading, (2) frictional shearing, or (3) decompression. Based on the structure and of pseudotachylite bodies and chemical composition of matrices at the Sudbury and Vredefort impact structures we show that these processes differ in time and space. We demonstrate that the cm- to km-scale bodies are effectively fragment- and melt-filled tension fractures that formed by differential rotation of target rock during cratering. Highly variable pseudotachylite characteristics can be accounted for by a single process, i.e., drainage of initially superheated impact melt into tension fractures of target rocks during late stages of crater formation.

Thursday, February 25, 2010 - Lecture Hall, 3:00 PM

Dan Durda, SwRI, Boulder, CO
TBA

March 2010

Thursday, March 11, 2010 - Lecture Hall, 3:00 PM

William T. Reach, Infrared Processing and Analysis Center (IPAC), Caltech
TBA

Thursday, March 18, 2010 - Lecture Hall, 3:00 PM

Dan Boice, SwRI, San Antonio, TX
TBA

April 2010

Thursday, April 8, 2010 - Lecture Hall, 3:00 PM

Devendra Lal, Scripps Institution of Oceanography, University of California at San Diego
TBA

Thursday, April 15, 2010 - Lecture Hall, 3:00 PM

Susan L. Brantley, Earth and Environmental Systems Institute, Penn State
TBA

Thursday, April 22, 2010 - Lecture Hall, 3:00 PM

Christine Floss, Washington University in St. Louis
TBA

May 2010

Thursday, May 6, 2010 - Lecture Hall, 3:00 PM

Scott Murchie, Applied Physics Laboratory
TBA

Thursday, May 13, 2010 - Lecture Hall, 3:00 PM

Amy Louise Morrow, Stanford University
TBA

Thursday, May 20, 2010 - Lecture Hall, 3:00 PM

Deanne Rogers, Stonybrook State University of New York
TBA

 

 

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