I propose to assist the osiris-REX mission team in the selection of an optimal sampling site through a detailed investigation of the secondary processing bennu's surface has experienced. Specifically,…

This is a grant awarded by the National Aeronautics and Space Administration (NASA) to the University of Texas at Austin for research to support the OSIRIS-REx mission to the asteroid Bennu. The goal of the research is to identify the optimal sampling site on Bennu's surface by investigating evidence of aqueous alteration and impact processing of the regolith, which is crucial for preserving any hydrous mineralogy and primitive organics. The research will leverage data from the OSIRIS-REx instruments, including thermal inertia, mineral abundances, and visible imagery, to create maps of aqueous alteration and impact processing that will aid the mission team in selecting the primary and secondary sampling sites. This work is valued at $279,522.18 and has an expected completion date of August 12, 2023. No set-aside designation is mentioned.

I propose to assist the osiris-REX mission team in the selection of an optimal sampling site through a detailed investigation of the secondary processing bennu's surface has experienced. Specifically, the proposed work focuses on identifying regolith that shows evidence of aqueous alteration and that has been comminuted through mechanical processes such as impact rather than through thermal fatigue from solar radiation that is expected to be a dominant process on neas like bennu. This is critical because the high temperatures associated with thermal fatigue will likely decompose and modify hydrous mineralogy and primitive organics, the latter's recovery being a key mission sampling objective. The goal of my work is to identify areas on bennu where reduced particle sizes, appropriate for sampling by the tag system, are associated with a moderate to strong degree of aqueous alteration and are most likely to be freshly exposed, impact-comminuted material that has preserved hydrous mineralogy and organics. To accomplish this goal i will use (1) regolith particle size and thermal inertia derived from otes, (2) mineral abundances derived from otes, (3) spectral indices from ovirs, and (4) ocams visible imagery. I will use particle size (or its proxy, thermal inertia) to characterize regolith production as solid surfaces become more comminuted with impact or thermal fatigue. The degree of aqueous alteration will be assessed using the relative abundances of phyllosilicates, anhydrous silicates, and the ratio of MG- to FE-bearing phyllosilicates as these have all been shown to vary systematically with degree of aqueous alteration among the CIS and CMS. These will be derived from both otes and ovirs and combined to create a robust map of aqueous alteration. Mineralogical evidence of thermal metamorphism, also derived from these instruments, will be used to flag areas of likely thermal metamorphism in the map. Regolith particle size and aqueous alteration will then be combined into a single impact processing map. Areas with the smallest particle size and a high degree of aqueous alteration (and no evidence of thermal metamorphism) are the most likely to be dynamically comminuted with minimal mineral or organic decomposition from solar radiative heating. I will also use ocams visible imagery to interpret and refine the maps as necessary. Global maps of aqueous alteration and impact processing will be delivered to the mission team to aid in the selection of the final two (primary and secondary) sampling sites. The analyses will be then repeated at higher resolution during reconnaissance to characterize the two sites. Because this work details the geologic history - aqueous alteration, impact, thermal fatigue, and thermal metamorphism - of bennu's surface materials, IT broadens existing investigations by going beyond individually mapped parameters (organics, mineralogy, particle size) to create new, derived geological data products. IT enhances the scientific return during the mission's asteroid-operational phase because IT is critical that this is done prior to site selection to make certain that a sample with the highest scientific value, and chance for preservation of organics, is collected. This work also provides testable hypotheses of the returned sample's geologic history. Finally, my experience in spectral analysis from inflight instruments and a 'ground truth' view from laboratory work of analog bennu material (CM chondrites) provides me with a unique, robust background to carry out meaningful science for the osiris-REX mission, to capably assist the team, and to increase the science return of the mission.