Wind erosion and transport on planetesimals

Abstract: We consider the possibility that aeolian (wind blown) processes occur on small, 1 to 100~km diameter, planetesimals when they were embedded in the protosolar nebula. Drag from a headwind within a protostellar disk is sufficiently large to loft cm and smaller sized particles off the surface of a 10 km diameter asteroid in the inner solar system (at a few AU), and micron sized particles off the surface of a 10 km diameter object in the Transneptunian region. The headwind is sufficiently strong to overcome surface cohesion in the inner solar system, but not in the outer solar system. However, in the outer solar system, surface particles can be redistributed or escape due to impacts from particles that are in the protosolar disk's wind. Based on scaling crater ejecta, we estimate that impacts from particles in the headwind will lead to erosion of mass rather than accretion for planetesimals below about 6 km in diameter. The erosion limit is independent of material strength but proportional to the wind velocity. We explore the sensitivity of splash particle trajectories to particle size, headwind velocity and Reynolds number. Winds from a protostellar disk could account for Kuiper Belt Object (486958) Arrokoth's smooth undulating terrain but only during an epoch of high particle flux and low wind velocity. These conditions could have been present during and just after coalescence of Arrokoth's building blocks.