LPI Seminar Series
Effective January 1, 2011, LPI seminars will be held on Fridays.
LPI seminars are held from 3:30–4:30 p.m. in the Lecture Hall at USRA, 3600 Bay Area Boulevard, Houston, Texas. Refreshments are served at 4:30 p.m. For more information, please contact Nicolas LeCorvec (phone: 281-486-2118; e-mail: email@example.com) or Paul Byrne (phone: 281-486-2140; e-mail: firstname.lastname@example.org). A map of the Clear Lake area is available here. This schedule is subject to revision.
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- Friday, May 29, 2015 - Lecture Hall, 3:30 PM
Simon Kattenhorn, ConocoPhillips and Louise Prockter, APL
Subduction on Jupiter’s Moon Europa: The Case for Plate Tectonics in the Ice Shell
Jupiter’s icy moon Europa has one of the youngest planetary surfaces in the Solar System, implying rapid recycling by some mechanism. Despite ubiquitous extension and creation of new surface area at dilational bands that resemble terrestrial mid-ocean spreading zones, there is little evidence of large-scale contraction to balance the observed extension or to recycle aging terrains. We address this enigma by presenting several lines of evidence that subduction may be recycling surface material into the interior of Europa’s ice shell. Using Galileo spacecraft images, we produce a tectonic reconstruction of geologic features across a 134,000 km2 region of Europa and find, in addition to dilational band spreading, evidence for transform motions along prominent strike-slip faults, as well as the removal of approximately 20,000 km2 of the surface along a discrete tabular zone. We interpret this zone as a subduction-like convergent boundary that abruptly truncates older geological features and is flanked by potential cryolavas on the overriding ice. We propose that Europa’s ice shell has a brittle, mobile, plate-like system above convecting warmer ice. Hence, Europa may be the only Solar System body other than Earth to exhibit a system of plate tectonics. These observations are in agreement with theoretical considerations that suggested the plausibility of convection-driven plate tectonics on Europa given its interior shell viscosity, thickness, and thermal structure.
- Friday, June 5, 2015 - Lecture Hall, 3:30 PM
Christian Klimczak, University of Georgia
Tectonic Geomorphology as a Tool to Understand the Structural Geologic History of the Moon
The Moon hosts several types of large-scale tectonic landforms that are indicative of both extensional and contractional tectonic deformation. High-resolution data returned from the Lunar Reconnaissance Orbiter (LRO) and Gravity Recovery and Interior Laboratory (GRAIL) missions allow us to assess these landforms in great detail. Extensional deformation is evident as large troughs that are interpreted to be graben structures. Grabens on Earth are generally found in rift settings, but also form as surface expressions of dike intrusions. Whether or not a graben is accompanied by a dike can be determined by a detailed analysis of their tectonic geomorphology. Contractional deformation, on the other hand, is manifest as prominent ridges, the largest of which are spatially associated with mare-filled impact basins. Ridges are believed to be the surface expression of one or more shallowly dipping thrust faults, with the ridge morphology representative of the thrust fault architecture at depth. The size and geometry of the landforms correlates with the size and geometry of the tectonic structures producing the landform, and so their morphologic characterization, coupled with numerical modeling provide a detailed set of observations and interpretations for deformation in the lunar subsurface. In this talk, I will show where large-scale graben are found to be associated with dike intrusions, and where mare ridges have been produced by large thrust faults that deeply penetrate the lunar lithosphere. These results increase our understanding of the regional and global tectonic evolution of our Moon in a quantitative manner.
- Friday, June 26, 2015 - Lecture Hall, 3:30 AM
Cyrena Anne Goodrich, Planetary Science Institute
Almahata Sitta and Other Polymict Ureilites and Why They are So Important
Almahata Sitta is the first meteorite observed to originate from an asteroid (2008 TC3) that had been tracked and studied in space before it hit Earth, providing an unprecedented opportunity to correlate properties of an asteroid with properties of the rocks derived from it. Almahata Sitta is also unique because the fallen fragments include a wide variety of different meteorite types. Approximately 70% belong to the ureilite group of achondrites, and 30% are various types of chondrites, including all major classes (ordinary, enstatite, carbonaceous, and also R-chondrites). Almahata Sitta has been classified as an anomalous polymict ureilite. However, maybe it is not so anomalous. Previously known (typical) polymict ureilites also contain a wide variety of foreign clast types. In this regard, all polymict ureilites differ from most other meteoritic breccias, in which the sole foreign clasts are CC matrix-like dark clasts. The foreign clasts in polymict ureilites represent at least 7 different parent asteroids and a wide range of chemical and isotopic environments in the early solar system. How did all these materials become mixed with fragments of ureilites in a single asteroid, and why is this process of mixing not apparent in most other meteorites? I will discuss several hypotheses and their disparate implications for early solar system processes.