M. Cristina De Sanctis and the VIR team Istituto di Astrofisica Spaziale e Planetologia INAF Roma Giornate della Planetologia Roma 2014

VIR Spectral Analysis: 2.8-µm Variations  Variations at 2.8 µm are spatially coherent  Darker material have deeper 2.8-µm band a b c d a b c d OH Giornate della Planetologia Roma 2014 In the interior from formation and through evolution. From in-falling material (comets and meteorites). Created from surface chemistry. Possible Sources of OH or H 2 O at the Surface or in the Interior

OH Anti-Correlation With Albedo Stronger 2.8-µm band associated with darker material  Support the hypothesis of infalling carbonaceous chondrites  May correspond to a different composition of the crust  This is different than what is observed on the Moon  Does it mean the process of formation is different? Stronger 2.8-µm band associated with darker material  Support the hypothesis of infalling carbonaceous chondrites  May correspond to a different composition of the crust  This is different than what is observed on the Moon  Does it mean the process of formation is different? Giornate della Planetologia Roma 2014 The 2.8-µm feature varies across Vesta’s surface. - General anti-correlation with albedo at all scales - Spatial distribution appears stable over time - No obvious correlation with surface temperature or latitude The 2.8-µm feature varies across Vesta’s surface. - General anti-correlation with albedo at all scales - Spatial distribution appears stable over time - No obvious correlation with surface temperature or latitude

Next stop: Ceres Giornate della Planetologia Roma 2014 Density/shape/albedo indicate Ceres is water- rich & underwent aqueous differentiation Water emission detected If a subsurface ocean formed, then the crust may have foundered Chemical evidence of aqueous alteration is expected McCord & Sotin (2005); Castillo- Rogez & McCord (2010) Primitive regolith with aqueous alteration products (e.g. Milliken and Rivkin, 2009) and subsurface ice (Fanale & Salvail, 1989)

Implicazioni per i processi di formazione Vesta: La distribuzione di OH su Vesta indica un processo primordiale molto importante e probabilmente diffuso nel sistema solare interno L’origine di questo OH è diverso dal caso lunare: legato agli impatti a bassa velocità di oggetti ricchi in acqua avvenuto nelle fasi primordiali del sistema solare Questo stesso processo può essere il responsabile del trasporto di acqua e di materiali organici sia nella fascia principale che sui pianeti terrestri Cerere: lo studio della distribuzione materiali idrati, l’eventuale presenza di sali, la struttura interna (oceano ?) saranno risultati essenziali per la comprensione dei processi primordiali di trasporto dell’acqua attraverso la snowline. Giornate della Planetologia Roma 2014