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Christie Jilly, Planetary Science and Exploration Seminar: "The OSIRIS-REx mission to Bennu: Bringing home fragments of the early Solar System"

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Nearly 4.6 billion years ago, the story of our Solar System began with the gravitational collapse of a giant molecular cloud, forming the proto-sun and a surrounding solar nebula. Within 10 million years of these humble beginnings, most of the gas and dust in the nebula had accreted into the sun or the surrounding planets, resembling the solar system we observe today. So how do we study these earliest stages of solar system formation, and the geologic processes that led to the diverse planets and even life on Earth? Meteorites have been recognized as important investigative tools in the field of cosmochemistry for over 200 years. In particular, a type of meteorite called carbonaceous chondrite offers a snapshot into the earliest formation processes, as they are mixtures of components that were present or formed in the early solar disk. However, these samples are rare, and the vast majority of found chondrites have endured thousands of years of terrestrial weathering that can obscure the primitive solar system record.

The OSIRIS-REx mission was proposed to directly return and analyze a sample of pristine carbonaceous asteroid regolith in an amount sufficient to study the nature, history, and distribution of its constituent material. The OSIRIS-REx spacecraft launched in 2014 and arrived at the B-class carbonaceous asteroid Bennu in 2018. After a series of asteroid observations to determine sample site selection, the spacecraft touched down on Bennu in 2020, collecting over 120g of material. The mission returned in September 2023, and within a year the observations have ranged from the expected to unexpected. The rock samples exhibit a mix of water and organic-rich phases, with very few anhydrous silicates remaining. Also present are abundant enigmatic phosphates that have yet to be identified. In this talk I’ll discuss these results from OSIRIS-REx and implications for processes in the early solar system.

Bio:

Christie Jilly is a Research Scientist and Lab Manager at Stanford University. Christie’s research interests are in geochemistry, mineralogy, and petrology of terrestrial and extra-terrestrial materials. Her technical expertise is in secondary ion mass spectroscopy (SIMS), and since 2019 she has served as the lab manager for both the Cameca NanoSIMS 50L instrument in the Stanford Nano Shared Facilities, as well as the SHRIMP-RG ion microprobe in the Department of Earth and Planetary Sciences. Some examples of her research include radiometric dating and oxygen isotopic analysis of carbonates in primitive chondrites to constrain timing and conditions of aqueous processes in the early solar system, U-Th-Pb dating and trace and rare element analysis of terrestrial zircons, and sulfur stable isotope analyses in sulfides to constrain formation histories and origins of ore deposits. Christie received her undergraduate degree in Astronomy (with a minor in graphic design) from the University of Southern California, and a Ph.D. in Geology and Geophysics from the University of Hawaii at Manoa where she specialized in isotopic analyses of meteoritic materials. She completed a postdoc at the UC Berkeley Space Sciences Laboratory, where she studied the chemical composition of comet grains and meteorites using a variety of microanalytical techniques such as FIB, TEM, and synchrotron XANES.

 

 

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