GRO 95577 (CR1) as a mineralogical analogue for asteroid (101955) Bennu

Victoria E. Hamilton, Hannah H. Kaplan, Harold C. Connolly Jr, Cyrena A. Goodrich, Neyda M. Abreu, Amy A. Simon

Available online 21 April 2022



• The only known CR1 meteorite is the best spectral analogue to B-type asteroid Bennu.
• The OSIRIS-REx mission may return a sample of an aqueously altered CR parent body.
• Other B-type asteroids also may be aqueously altered CR parent bodies.
• CR parent bodies contain substantial amounts of H2O and OH and exotic organics.”

“Orbital spectra collected of asteroid (101955) Bennu by NASA’s Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer (OSIRIS–REx) spacecraft have identified ungrouped C, CI, and CM meteorites having petrologic types 1, 1/2, and 2 as the best mineralogical analogues to Bennu to date. Here we present spectral evidence that Grosvenor Mountains (GRO) 95,577, a CR1, is a better analogue for Bennu’s bulk surface mineralogy. CR-like parent bodies are targets of interest because they contain some of the most pristine materials from the solar nebula and can contain substantial amounts of H2O and OH− in addition to exotic organics. Unfortunately, terrestrial weathering makes constraining their indigenous mineralogy and organics challenging. Analysis of samples retrieved directly from an asteroid would help us disentangle the effects of terrestrial weathering and asteroidal aqueous alteration and hence whether some of the exotic organics and large populations of presolar grains were affected by terrestrial processes in meteorites. If Bennu is comprised of CR1(−like) material, in whole or in part, the OSIRIS–REx returned sample represents a tremendous opportunity to explore in depth what is currently a unique material among carbonaceous chondrites.”