Space weathering of carbonaceous asteroids

Two missions are currently en route to collect and return samples from carbonaceous asteroids and return them to Earth. The OSIRIS-Rex mission (NASA) will sample Bennu, whereas Hayabusa2 (Japan Aerospace Exploration Agency, JAXA) will visit the asteroid Ryugu. Both asteroids have affinities to the carbonaceous chondrite meteorites. As they are composed of anhydrous and hydrous silicate minerals together with water and organic molecules, these meteorites are of particular interest with regards to the delivery of biologically important molecules to early Earth and Mars. The missions will collect samples of fine-grained regolith that have been to 'space weathered'; this term describes a group of processes that physically and chemically alter the surfaces of airless bodies. The effects of space weathering on carbonaceous asteroids are very poorly understood. Therefore in preparation for the sample return missions, considerable efforts are being made to understand space weathering, for example by using spectroscopic measurements of asteroids and laboratory laser/ion irradiation experiments. This project seeks to test and ground-truth results from these studies by studying samples of carbonaceous asteroid regoliths that are available as the CM carbonaceous chondrite meteorites.