In this ApJ Letter, we combined petrographic observations and novel O-isotopic measurements of CM carbonates to track the evolution of the alteration temperature. An intriguing question regarding the early geologic evolution of water-rich asteroids is how these airless bodies thermally evolved after their accretion due to 26Al decay. We found that such water-rich asteroids experienced temperatures no higher than 250 °C during their progressive thermal evolution. These results are important because they (i) imply that hydrated asteroids accreted late in the protoplanetary disk (as their earlier accretion would have led to higher alteration temperatures due to increased concentrations of radioactive 26Al) and (ii) constrain the thermal histories of the asteroids Bennu and Ryugu, which are currently being sampled by the international space missions OSIRIX-REx and Hayabusa2.
Publisher link: https://iopscience.iop.org/article/10.3847/2041-8213/ab3bd0
Free access link: https://hal.univ-lorraine.fr/hal-02331795v1/file/Vacher.pdf