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.

November 2009

Thursday, November 12, 2009 - Lecture Hall, 3:00 PM

Cin-Ty A. Lee, Rice University
Planetary magmatism, plate tectonics, and stagnant lids: insights from the Earth

Thursday, November 19, 2009 - Lecture Hall, 3:00 PM

George J. Flynn, SUNY Plattsburgh, NY
Organic rims on individual grains in chrondritic porous IDPS: Constraints on the origin of pre-biotic organic matter

Chondritic, porous interplanetary dust particles (CP IDPs) are the most primitive samples of extraterrestrial material available for laboratory analysis. These ~10 micrometer CP IDPs are unequilibrated aggregates of mostly submicron, anhydrous grains of a diverse variety, including olivine, pyroxene, glass, and sulfide. These individual grains in these CP IDPs are coated by layers of carbonaceous material, typically ~100 nm thick, which holds the grains together. Carbon XANES maps of ultramicrotome sections from several CP IDPs were obtained by X-ray Absorption Near-Edge Structure (XANES) spectroscopy using the Scanning Transmission X-Ray Microscope (STXM). Cluster analysis, which compares spectra from each pixel in the map and identifies groups of pixels exhibiting similar spectra, indicates most of the carbonaceous grain coatings are organic and have very similar C-XANES spectra, with the two strongest absorption features resulting from the C=C and C=O functional groups. This organic matter coats the individual grains, implying an assembly sequence beginning with grain formation, followed by the emplacement of the organic coating, and finally the assembly of the primitive dust particles. Thus, the organic grain coatings in the primitive CP IDPs appear to have formed prior to the aggregation of the most primitive dust of our Solar System, indicating that these grain coatings are the oldest surviving samples of the pre-biotic organic matter in our Solar System. The thickness and C-XANES spectrum for the coatings on all grains in an individual CP IDP are very similar, independent of the mineralogy of the underlying grain. This indicates that mineral specific catalysis (e.g., the Fischer-Tropsch process), one of the widely accepted models for organic formation in the early Solar System, was not the production mechanism for the primitive, pre-biotic organic matter that coats the grains in the CP IDPs. This result is consistent with the alternative model, that primitive organic matter was produced by irradiation of carbon-bearing ices that condensed on the grain surfaces.

Friday, November 20, 2009 - Lecture Hall, 3:00 PM

Br. Guy Consolmagno, Vatican Observatory
The Thermal and Physical Properties of Meteorites: Review and New Results

Basic physical data on the density, porosity, strength, and thermal properties of meteorites are essential to understand and model many aspects of small solar system objects, including the physical state of asteroids, thermal histories of outer solar system bodies, the spin and evolution of comets, and the nature of bolides. Density and porosity are the best-determined values for meteorites, and have been reasonably well characterized for all meteorite types; our latest results will be reviewed here. Thermal properties have only been measured for a few meteorite samples; new research in this area is ongoing and should provide data useful for understanding the thermal response of asteroids and the thermal evolution of asteroids and small moons. Future work should also include strength measurements, essential for understanding both impact phenomena and terrestrial bolides. We can also begin to discuss typical error in the laboratory data and caveats in applying these data to astrophysical situations.

December 2009

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

John Grant, Smithsonian Institution
TBA

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

 

 

     Site Map | Contact Us | Privacy Policy | ©Lunar and Planetary Institute, 2009