Global variations in regolith properties on asteroid Vesta from Dawn’s low-altitude mapping orbit.
Denevi, B. W., Beck, A. W., Coman, E. I., Thomson, B. J., Ammannito, E., Blewett, D. T., Sunshine, J. M., De Sanctis, M. C., Li, J.-Y., Marchi, S., Mittlefehldt, D. W., Petro, N. E., Raymond, C. A. and Russell, C. T. (2016),
Meteoritics & Planetary Science. doi: 10.1111/maps.12729
Version of Record online: 22 SEP 2016
“We investigate the depth, variability, and history of regolith on asteroid Vesta using data from the Dawn spacecraft. High-resolution (15–20 m pixel−1) Framing Camera images are used to assess the presence of morphologic indicators of a shallow regolith, including the presence of blocks in crater ejecta, spur-and-gully–type features in crater walls, and the retention of small (<300 m) impact craters. Such features reveal that the broad, regional heterogeneities observed on Vesta in terms of albedo and surface composition extend to the physical properties of the upper ~1 km of the surface. Regions of thin regolith are found within the Rheasilvia basin and at equatorial latitudes from ~0–90°E and ~260–360°E. Craters in these areas that appear to excavate material from beneath the regolith have more diogenitic (Rheasilvia, 0–90°E) and cumulate eucrite (260–360°E) compositions. A region of especially thick regolith, where depths generally exceed 1 km, is found from ~100–240°E and corresponds to heavily cratered, low-albedo surface with a basaltic eucrite composition enriched in carbonaceous chondrite material. The presence of a thick regolith in this area supports the idea that this is an ancient terrain that has accumulated a larger component of exogenic debris. We find evidence for the gardening of crater ejecta toward more howarditic compositions, consistent with regolith mixing being the dominant form of “weathering” on Vesta."