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Lunar and Planetary Institute

LPI Seminar Series

2019

LPI seminars will be held on Thursdays.

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 Nicholas Castle (phone: 281-486-2144; e-mail: castle@lpi.usra.edu) or Julia Semprich (phone: 281-486-2180; e-mail: jsemprich@lpi.usra.edu.) A map of the Clear Lake area is available here. This schedule is subject to revision.

Join the LPI-Seminars mailing list to receive email notifications about upcoming LPI Seminars. To join the mailing list please send an email to:
lpi-seminars-join@lists.hou.usra.edu.

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.

January 2019

Thursday, January 24, 2019 - Lecture Hall, 3:30 PM

Steven J Desch, Arizona State University
LPI Seminar: Ureilite Diamonds from Mars’s Core: A Tale of Three Planets, None of Them Lost
Recent analyses of mineral inclusions inside ~100 μm diamonds from the Almahata Sitta ureilite meteorite show they formed at pressures > 21 GPa, demanding origin inside a planet. We argue the diamonds are exogenous to the ureilite parent body (UPB) and instead formed at Mars’s core-mantle boundary. After floating to the top of Mars’s magma ocean, they and other materials were ejected in the Borealis basin impact early in Mars’s evolution. One fragment struck the UPB, which until then resembled other meteorite parent bodies like Vesta. The impact catastrophically disrupted the UPB. Mixing of Martian surface materials with the UPB material gave ureilites many of their unusual characteristics. We identify the asteroid 15 Eunomia as potentially the largest remnant of the collision, and 438 Zeuxo as a possible source of Almahata Sitta. We identify a dynamical pathway for delivery of ureilites to Earth. Ureilites may contain the only known samples of a planetary core.

February 2019

Tuesday, February 12, 2019 - Lecture Hall, 3:30 PM

Seungyeol Lee, University of Wisconsin-Madison
LPI Seminar: Application of Combined Techniques for Studying Nano-Minerals in Geological System
Modern technology allows us to detect, characterize, and understand the nature of nano-minerals. However, it is still challenging to determine its structure at the nanoscale when structures include the short-range ordering, defects, and local domains. I used integrated techniques (X-ray/Neutron diffraction, Pair distribution function, TEM, Z-contrast imaging) for solving this problem and applied some nano-minerals in geological environments. This presentation will several research examples: new nano-mineral observation (luogufengite and valleyite), crystal structure of minerals (6-line ferrihydrite, vernadite and low-temperature tridymite/cristobalite), nano-structure enhancing magnetic coercivity (lodestone and hemo-ilmenite).
Thursday, February 14, 2019 - Lecture Hall, 3:30 PM

Joelle Reiser, Pacific Northwest National Laboratory
LPI Seminar: Comparative Structural Investigations of Nuclear Waste Glass Alteration Layers and Sol-gel Synthesized Aerogels
Nuclear reactors provide reliable energy, but resultant nuclear waste requires safe disposal. Borosilicate glass is a current immobilization method, incorporating nuclear waste products into glass matrices. Understanding alteration mechanisms in aqueous media is essential to nuclear waste performance assessments to ensure radioisotopes are contained for extended periods of time. When exposed to aqueous solutions, borosilicate glass releases various ions into solution and alteration products (or alteration layers) are formed at the surface of glasses. Although the nuclear glass alteration community has agreed on the mechanisms during initial dissolution, the general mechanisms of the formation of alteration layers and their role in long-term glass alteration are still being debated. More information on physical properties of the alteration layers is needed to further the understanding of their impacts on overall glass alteration. In this work, pore volumes and solid structures of glass alteration layers formed in solutions of various pH conditions are evaluated with small angle X-ray scattering (SAXS). Solid structures of alteration layers are compared to those of synthetic aerogels of comparable compositions produced under various pH conditions. Alteration layers formed at pH 11 were shown to contain large structures (>10 nm) similar to synthetic aerogels created under neutral and basic conditions whereas alteration layers formed at pH 9 did not. The large structures formed at pH 11 are proposed to be caused by excessive free Si species through Ostwald Ripening.
Tuesday, February 19, 2019 - Lecture Hall, 3:30 PM

LPI Seminar: Alvaro Crósta (State University of Campinas, Brazil
The impact record of South and Central America: An updated review
The Earth’s impact record is known to be rather limited in both time and space. There are about 190 impact structures currently known on Earth, representing a minor fraction of all the impact events that contributed to the initial formation of our protoplanet, and then to formation and modification of the surface of the planet. Moreover, the distribution of impact structures on Earth is manifestly uneven. Two continents that stands out for their relatively small number of confirmed impact structures and impact ejecta occurrences are South and Central America. The limited impact record for this large continent makes a robust case that there is a significant potential for further discoveries. A summary of the current knowledge of the impact record of these continents will be presented covering also some occurrences of impact glasses in Argentina, Chile, Uruguay and, possibly, Colombia, as well as occurrences of distal deposits from the K-Pg boundary event that formed the Chicxulub structure in Mexico.
Monday, February 25, 2019 - Lecture Hall, 3:30 PM

Bradley J. Thomson, University of Tennessee
LPI Seminar: Crater-hosted Deposits on Mars and Moon: Targets for Science and Exploration
In this talk, I will discuss geologic context and history of materials with Gale crater on Mars and numerous polar craters on the Moon. In each case, we can analyze the present-day geology and geomorphology with a variety of techniques to infer elements of their past history. The Mars Science Laboratory rover Curiosity has been exploring the layered central mound within Gale crater on Mars from 2012 to the present. On the Moon, numerous impact structures near the lunar poles lie in permanent shadow and may host ice, although interpretations from several ground- and spacecraft-based observations diverge on the nature of these putative ice deposits.

March 2019

Tuesday, March 5, 2019 - Lecture Hall, 3:30 PM

Sally L. Potter-McIntyre, Southern Illinois University
LPI Seminar: Subsurface Habitability on Earth and Mars
The subsurface of Earth is a habitable environment that contains a large portion of the total biomass on this planet. Similarly, the subsurface of Mars may represent a past or even present habitable environment. Accessibility of the subsurface is challenging on both planets, but nevertheless, understanding the variability of subsurface fluids and water/rock/biota interactions occurring in these environments is crucial because this understanding informs both present conditions for habitability as well as the evolution of these environments over geologic time. Most terrestrial subsurface research focuses on drill cores, deep sea drilling, or cave or mine research; however, drilling and cave research are not likely to occur on Mars in the near future, so it is imperative that we are able to glean clues about the martian subsurface from surficial evidence. My research investigates ways to identify fingerprints of subsurface fluid/rock/biota in exposed examples and two case studies are presented: diagenetic jarosite, and magmatic intrusions into sulfur-rich sedimentary rocks.

 

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