Why a sample return mission?

What we know of asteroids, we have learned through telescopic observations and laboratory analysis of meteorites, the fragments of asteroids that travel through the Earth’s atmosphere, land and are recovered. Telescopic observations can tell scientists a lot – even about these very dim objects: Scientists analyze data they collect to construct models of mass, density, rotation and composition. From meteorite analyses, researchers can determine composition, density, mass and create models of the parent bodies and their formation and history.

Telescopic observations, lab analyses and models will be concretely linked by bringing a physical sample of an asteroid back to the lab to study. From such study, scientists will be able to ground-truth – to confirm the facts with an actual field check! Were the assumptions and conclusions used to create the models correct or do they need to be revised?