240-1 Complementary Datasets Link the Physical and Chemical Evolution of Bennu Particle OREX-800084-0 via Aqueous Alteration

Session: From Atoms to Asteroids and Habitable Planets: Coordinated Analysis of Planetary Samples and Their Terrestrial Analogues

Presenting Author:

Kelly Miller

Authors:

Miller, Kelly E.¹, Hanna, Romy², Hibbitts, Charles³, Núñez, Jorge Ivan⁴, Edey, Dave⁵, Takir, Driss⁶, Whittington, Alan⁷, Wagoner, Carlie⁸, Seelos, Frank⁹, Stevanovic, Ana¹⁰, Nagashima, Kazuhide¹¹, Huss, Gary¹², Phillips-Lander, Charity¹³, Domanik, Kenneth¹⁴

(1) Southwest Research Institute, San Antonio, TX, USA, (2) University of Texas at Austin - Jackson School of Geosciences, Austin, TX, USA, (3) Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA, (4) Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA, (5) University of Texas at Austin - Jackson School of Geosciences, Austin, TX, USA, (6) Amentum, NASA JSC, Houston, TX, USA, (7) University of Texas at San Antonio, San Antonio, TX, USA, (8) Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA, (9) Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA, (10) University of Texas at San Antonio, San Antonio, TX, USA, (11) University of Hawaii at Manoa, Honolulu, HI, USA, (12) University of Hawaii at Manoa, Honolulu, HI, USA, (13) Southwest Research Institute, San Antonio, TX, USA, (14) University of Arizona, Tucson, AZ, USA,

Abstract:

A primary advantage of sample return is the opportunity to obtain unique insights by linking large-scale and  fine-scale measurements through the application of coordinated analyses. The OSIRIS-REx mission returned samples from asteroid Bennu in September 2023 after more than two years observing the asteroid. These orbital data revealed the presence of bright veins 10s of cm in length that are spatially associated with a 3.4 µm absorption band interpreted as the presence of carbonate minerals (Kaplan et al. 2020). Such large features suggest widespread fluid flow. Our team is performing coordinated analysis of returned sample OREX-800084-0, which is a 113-mg, 9-mm particle. Our project aims to characterize aqueous alteration of the sample, and to assess whether the features observed in the particle show evidence for open scale processes. To do so, we utilize multiple datasets from the particle. XCT analysis revealed the presence of at least two major lithologies, which are distinguished primarily by different abundances of Fe-rich phases. Both lithologies show evidence for aqueous alteration, and the sample records potential evidence of multiple aqueous alteration environments. Microscopic multispectral imaging of the whole particle at 30-µm resolution allows us to map mineralogy associated with the two lithologies at the grain surface. The compositions of regions of interest in the multispectral maps are analyzed in more detail with microscopic Fourier transform infrared spectroscopy. These data have confirmed the presence of Mg-rich serpentine via a 2.72-µm band, as well as dolomite grains at 3.4 µm. Xe XCT analysis (Hanna et al. 2022) provides the spatial distribution of porosity within the two lithologies. Porosity is calibrated using He pycnometry. The particle will subsequently be made into thin sections, which can be mapped to the XCT data to retain 3-dimensional information. The sections will be chemically mapped using SEM-EDX and EPMA to identify carbonate grains and other products of aqueous alteration. O and C isotopic analysis of secondary minerals will provide constraints on the degree of water-rock interaction, temperature, and whether fluid evolution is open- or closed-system. Finally, Raman analyses will identify whether carbonates and organics are spatially associated on ~100 µm scales, and constrain thermal evolution of the organics. Together, these complementary datasets provide important constraints on the chemical and physical evolution of Bennu via aqueous alteration.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9510

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