TY  - JOUR
ID  - Marsset2020
T1  - The violent collisional history of aqueously evolved (2) Pallas
A1  - Marsset, Michaël
A1  - Brož, Miroslav
A1  - Vernazza, Pierre
A1  - Drouard, Alexis
A1  - Castillo-Rogez, Julie
A1  - Hanuš, Josef
A1  - Viikinkoski, Matti
A1  - Rambaux, Nicolas
A1  - Carry, Benoît
A1  - Jorda, Laurent
A1  - Ševeček, Pavel
A1  - Birlan, Mirel
A1  - Marchis, Franck
A1  - Podlewska-Gaca, Edyta
A1  - Asphaug, Erik
A1  - Bartczak, Przemyslaw
A1  - Berthier, Jérôme
A1  - Cipriani, Fabrice
A1  - Colas, François
A1  - Dudziński, Grzegorz
A1  - Dumas, Christophe
A1  - Durech, Josef
A1  - Ferrais, Marin
A1  - Fétick, Romain
A1  - Fusco, Thierry
A1  - Jehin, Emmanuel
A1  - Kaasalainen, Mikko
A1  - Kryszczynska, Agnieszka
A1  - Lamy, Philippe
A1  - Le Coroller, Hervé
A1  - Marciniak, Anna
A1  - Michalowski, Tadeusz
A1  - Michel, Patrick
A1  - Richardson, Derek C.
A1  - Santana-Ros, Toni
A1  - Tanga, Paolo
A1  - Vachier, Frédéric
A1  - Vigan, Arthur
A1  - Witasse, Olivier and Yang, Bin
JA  - Nature Astronomy
Y1  - 2020
VL  - 4
SP  - 569
EP  - 576
AD  - 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
SN  - 2397-3366
UR  - https://ui.adsabs.harvard.edu/abs/2020NatAs...4..569M
N2  - 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 measurement<SUP>1</SUP> being compatible within error bars with the icy Ceres (2.16 ± 0.01 g cm<SUP>-3</SUP>)<SUP>2</SUP> and the other<SUP>3</SUP> compatible within error bars with the rocky Vesta (3.46 ± 0.03 g cm<SUP>-3</SUP>)<SUP>4</SUP>. Here we report high-angular-resolution observations of Pallas performed with the extreme adaptive optics-fed SPHERE imager<SUP>5</SUP> 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<SUP>-1</SUP> on Pallas—compared with an average of ~5.8 km s<SUP>-1</SUP> 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<SUP>-3</SUP> (1σ uncertainty) is fully compatible with a CM chondrite-like body, as suggested by its spectral reflectance in the 3 μm wavelength region<SUP>6</SUP>. 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. <SUP>7,8</SUP>), although alternative origins are conceivable.
M1  - ={10.1038/s41550-019-1007-5}
ER  -