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: firstname.lastname@example.org) or Paul Byrne (phone: 281-486-2140; e-mail: email@example.com). 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:
- Tuesday, March 3, 2015 - Lecture Hall, 3:30 PM
Dating Impact Craters: What Can Precise and Accurate Ages Teach Us?
Impacts have played a major role in the evolution of planetary bodies and asteroids in the Solar System. About 188 impact structures – large and small, old and young – are currently known on Earth. The improvements in isotopic dating methods, in addition to stratigraphic age constraints, now offer an increasingly precise and accurate set of age data for a number of impact events on our planet. In this seminar I will present a synthesis of recent findings, current challenges and open questions in terrestrial impact crater geochronology mainly based on the 40Ar/39Ar dating technique, with examples from the North American, European and Australian impact cratering record. Precise and accurate impact ages are crucial when it comes to the potential link between large meteorite impacts, mass extinctions and biodiversification events; evidence for binary asteroid impacts and multiple impact events in the geologic record; and the nature and longevity of hydrothermal activity in cooling impact craters as hosts for economic deposits and niches for microbial life.
- Friday, March 6, 2015 - Lecture Hall, 3:30 PM
Walter Kiefer, Lunar and Planetary Institute
Preservation of Isotopic Heterogeneity in a Convecting Martian Mantle
The existence of volcanic activity on Mars in the last 200 million years is demonstrated by both the low crater densities on volcanos such as Olympus Mons and by radiometric dating of the shergottite meteorites. This implies the existence of adiabatic decompression melting and thus an actively convecting mantle. On the other hand, the preservation of isotopically distinct reservoirs that formed in the first 100 million years of solar system history has been interpreted by some investigators as evidence that the martian mantle cannot be convecting. This apparent paradox can be resolved by considering the effects of geographic isolation of isotopic reservoirs and of inefficient convective mixing, which together allow geochemical reservoirs to be preserved within a convecting martian mantle.