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Applicant -- Exploring geologic processes in solar system materials using mineralogy, petrology, and geochemistry

Wednesday, March 2, 2016
Gretchen
Benedix-Bland
Earth travels through a storm of debris as it orbits the Sun:
asteroidal and cometary material that enters our atmosphere at up to
70km/s. Much of it is primordial, dating from the earliest period of solar
system history.  The meteorites that fall to Earth are from this
population. They are the oldest rocks in existence, containing the 4.56
billion year record of solar system formation and evolution, and the
processes that produced the terrestrial planets. Meteorites represent the
entire compositional diversity of the inner solar system, but we rarely
have details about where they come from. We can make general and specific
inferences by constraining the processes they have affected the rocks.
Aqueous mineralogy tells us that there was some form of H2O on asteroids ­
different meteorites have differing amounts of altered material, implying
that aqueous processes were heterogenous in the system. Lots of meteorites
show shock effects, again to varying degrees, which helps us to decipher
the importance of impact in geologic processing of solar system materials.
 In addition to aqueous and impact processes, there is evidence of heat in
meteorites ­ from metamorphic levels to outright melting.  The details of
mineral chemistries in these types of rocks allow us to constrain
pressures and temperatures, which allow us to infer parent body sizes.  I
unravel the effects of these processes in different meteorite types using
a multidisciplinary toolbox that includes mineralogy, petrology,
geochemistry, geochronology, and μ-spectroscopy. I will describe my
research over the past 20 years to show how this is done.


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