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 Susanne Schwenzer (phone: 281-486-2114; e-mail: schwenzer@lpi.usra.edu) or Steve Clifford (phone: 281-486-2146; e-mail: clifford@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.
July 2009
- Thursday, July 9, 2009 - Lecture Hall, 3:00 PM
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Michael D. Max, Marine Desalination Systems, L.L.C.
Gas Clathrate (Hydrate); Nature's Gas Sequestration MechanismGas hydrates are solid crystalline, container compound materials formed from a cage structure of water molecules hosting gas molecules in structural voids. A weak van der waals bonding stabilizes the structure. During formation, the chemical reaction of hydrate formation strongly rejects dissolved ionic and very small suspended sold materials to a much greater extent than ice, whose crystallization is a phase change involving no other materials than water molecules. All the hydrate cages do not have to be filled for the hydrate structure to be stable. Almost all gases can form hydrate. Each has a unique field of pressure and stability, although many of the common gas hydrate stability fields overlap considerably. When the concentration of any hydrate former rises to a certain level of saturation, hydrate will form. Hydrate formation can alter local pH; when hydrate forming materials, for instance H2S and SOx, the solid material extracts the materials into the almost chemically inert hydrate form. When hydrate forms from a mixture of gases, they are incorporated into the hydrate according to their preference so that the resulting hydrate has a different ratio of gas components than the mixture from which it formed. This is a little-known natural process of gas separation. On earth, the economically interesting natural gas hydrate forms in marine aqueous environments when natural gas (mainly methane) flux in water rises to an appropriate level in its field of P-T stability. This sequesters methane, which is an important greenhouse gas, from reaching the atmosphere or otherwise affecting the CO2 balance and may be an important mechanism within Gaia. In other locales, such as in a gas pipeline, when dissolved water reaches an appropriate concentration in the gas, unwanted hydrate formation takes place. Hydrate physical chemistry and the abundance of hydrate forming materials can be anticipated throughout the universe wherever the three conditions for hydrate formation (pressure-temperature-concentration) occur. Likely hydrate occurrences could be on Titan, the proposed hidden sea beneath the ice crust of Encaledus, and particularly in the upper crust of Mars, amongst other locales in our solar system. Natural gas hydrate may confer a resource-rich character to planets and moons previously characterized as resource-poor, and be a key to acceleration of human exploration of the solar system.
- Thursday, July 16, 2009 - Lecture Hall, 3:00 PM
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Alice LeGall, Jet Propulsion Laboratory
Cassini SAR and radiometric observation of TitanIn addition to a high-resolution synthetic-aperture radar imager (SAR), a lower resolution scatterometer and a profiling altimeter, the Cassini Radar includes a passive mode: the radiometry channel that is able to observe simultaneously with, or separately from, the active measurements. Over the last 4 years, almost all Titan’s surface 2.2 cm-microwave emission has been observed in this operational mode. Among these measurements, ~35% of the surface has been observed near closest approach enabling the construction of a high-resolution mosaiced map of the brightness temperature corrected to normal incidence. The emissivity and the reflectivity of surface features are generally anticorrelated. Correlation of the radiometry data acquired near closest approach, with active radar, addresses a number of compositional and geological questions. In this seminar we will present the theoretical background and main results of the joint analysis of the passive and active Cassini Radar data. In particular, we’ll show that backscatter from some bright regions of Titan cannot be explained by existing models. We will explore one candidate for the anomalous backscatter that has a plausible geological basis for bright channels recently observed.
- Thursday, July 30, 2009 - Lecture Hall, 3:00 PM
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David Vaniman, Los Alamos National Lab
Mineralogic Aspects of Mars vs. Earth HydrogeologyAmong the terrestrial planets, Mars is most Earth-like in the nature of its hydrosphere. However, there are many aspects of the martian hydrosphere that limit comparison. Stagnation. Cold conditions and absence of plate tectonics to cycle wet sediment into the lithosphere results in static deep groundwater system with drier host rock. Slow reaction rates, disequilibrium assemblages, and pathway-dependent reactions are likely more prevalent on Mars than on Earth. Minerals formed in the martian hydrosphere that would have limited “lifespans” on Earth (e.g., smectites, zeolites) may persist on Mars indefinitely. Severe obliquity cycles. Massive redistribution of ice on Mars follows obliquity excursions of a magnitude not seen on Earth. Subglacial and periglacial processes are thus relatively more significant on Mars. Low water/rock ratios. Fluvial geomorphology on Mars points to high-energy environments with evidence of persistent standing bodies of water elusive. At dispersed and low water/rock ratios the mineralogy of the hydrosphere is likely dominated by soluble salts. However, evidence of abundant clay minerals suggests higher water/rock ratios in the past. A challenge to understanding the martian hydrosphere is in development of credible models for what appears to have once been a much wetter environment and building testable conceptual models of mineralogy that could have formed in that wetter hydrosphere.
August 2009
- Tuesday, August 4, 2009 - Berkner Room, 3:00 PM
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Timothy Swindle, Univ. of Arizona
TBA - Thursday, August 13, 2009 - Lecture Hall, 3:00 PM
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Bruce Banerdt, Jet Propulsion Laboratory
TBA - Thursday, August 20, 2009 - Lecture Hall, 3:00 PM
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Veronika Heber, UCLA, Dept. of Earth and Space Sciences
TBA - Thursday, August 27, 2009 - Lecture Hall, 3:00 PM
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Paul Weissman, Jet Propulsion Laboratory
TBA
September 2009
- Thursday, September 3, 2009 - Lecture Hall, 3:00 PM
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Horton Newsom, Institute of Meteoritics and Dept. of Earth and Planetary Sciences, University of New Mexico
TBA - Thursday, September 10, 2009 - Lecture Hall, 3:00 PM
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Kurt Marti, University of California, San Diego
TBA - Thursday, September 17, 2009 - Lecture Hall, 3:00 PM
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Jerry Delaney
TBA - Thursday, September 24, 2009 - Lecture Hall, 3:00 PM
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Dan Durda, Southwest Research Institute, Boulder, CO
TBA
October 2009
