SPACE-WEATHERING ON PRIMITIVE BODIES: A MULTI-SCALE LABORATORY STUDY ON WEATHERED GRAINS

Studying small bodies in our Solar System is fundamental for understanding its origin and evolution. These small "primitive" bodies are undifferentiated: their components did not sepa-rate according to their density, irreversibly modifying their mineralogy. They have evolved very little since their formation, yielding a com-position relatively close to that of the primordial proto-planetary disk [1]. However, other pro-cesses such as thermal alteration, aqueous alter-ation, shocks, or space weathering (SpWe) can affect these bodies' surfaces. In particular, the spectral changes induced by surface weathering can bias and complicate compositional studies led by remote sensing. Therefore, it is para-mount to understand how these processes can affect the surface of primitive asteroids. These bodies can be studied remotely by acquiring spectroscopic data, but it is also possible to conduct laboratory investigations on analogous samples such as certain classes of meteorites (carbonaceous chondrites, CCs [2]), terrestrial analogs (hydrated silicates - which dominate the mineral composition of "primitive" bodies [3]), or directly on returned materials brought back by sample return missions (such as the Haya-busa2 (JAXA) and OSIRIS-REx (NASA) mis-sions [4–6]). In this work, we emulate the effects of solar particles on the surface of primitive asteroids in a laboratory environment by conducting ion-implantation experiments (INAF-OACT). We use a 400 keV Ar⁺ flux to weather a mm-sized grain from the carbonaceous chondrite C2-ung Tagish Lake meteorite. The Tagish Lake mete-orite has been chosen since its properties, such as density and H abundance, are compatible with those of the surface of the B-type asteroid Bennu, the target of the OSIRIS-Rex mission (NASA - [8, 9])