Global variations in regolith properties on asteroid Vesta from Dawn's low-altitude mapping orbit
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- 作者：Brett W. Denevi ; Andrew W. Beck ; Ecaterina I. Coman ; Bradley J. Thomson ; Eleonora Ammannito ; David T. Blewett ; Jessica M. Sunshine ; Maria Cristina De Sanctis ; Jian-Yang Li ; Simone Marchi ; David W. Mittlefehldt ; Noah E. Petro ; Carol A. Raymond and Christopher T. Russell
- 刊名：Meteoritics & Planetary Science
- 出版年：2016
- 出版时间：December 2016
- 年：2016
- 卷：51
- 期：12
- 页码：2366-2386
- 全文大小：2437K
- ISSN：1945-5100
文摘
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.