The violent collisional history of aqueously evolved (2) Pallas
| Type of publication: | Article |
| Citation: | Marsset2020 |
| Publication status: | Published |
| Journal: | Nature Astronomy |
| Volume: | 4 |
| Year: | 2020 |
| Month: | feb |
| Pages: | 569--576 |
| Address: | AA(Department of Earth, Atmospheric and Planetary Sciences, MIT, Cambridge, MA, USA; Astrophysics Research Centre, Queen's University Belfast, Belfast, UK), AB(Institute of Astronomy, Charles University, Prague, Czech Republic), AC(Aix Marseille Univ, CNR |
| ISSN: | 2397-3366 |
| URL: | https://ui.adsabs.harvard.edu/... |
| Abstract: | Asteroid (2) Pallas is the largest main-belt object not yet visited by a spacecraft, making its surface geology largely unknown and limiting our understanding of its origin and collisional evolution. Previous ground-based observational campaigns returned different estimates of its bulk density that are inconsistent with one another, one measurement1 being compatible within error bars with the icy Ceres (2.16 ± 0.01 g cm-3)2 and the other3 compatible within error bars with the rocky Vesta (3.46 ± 0.03 g cm-3)4. Here we report high-angular-resolution observations of Pallas performed with the extreme adaptive optics-fed SPHERE imager5 on the Very Large Telescope. Pallas records a violent collisional history, with numerous craters larger than 30 km in diameter populating its surface and two large impact basins that could be related to a family-forming impact. Monte Carlo simulations of the collisional evolution of the main belt correlate this cratering record to the high average impact velocity of ~11.5 km s-1 on Pallas—compared with an average of ~5.8 km s-1 for the asteroid belt—induced by Pallas's high orbital inclination (i = 34.8°) and orbital eccentricity (e = 0.23). Compositionally, Pallas's derived bulk density of 2.89 ± 0.08 g cm-3 (1σ uncertainty) is fully compatible with a CM chondrite-like body, as suggested by its spectral reflectance in the 3 μm wavelength region6. A bright spot observed on its surface may indicate an enrichment in salts during an early phase of aqueous alteration, compatible with Pallas's relatively high albedo of 12-17% (refs. 7,8), although alternative origins are conceivable. |
| Userfields: | ={10.1038/s41550-019-1007-5}, |
| Keywords: | |
| Authors | |
| Added by: | [JoH] |
| Total mark: | 0 |
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