Asteroid (16) Psyche, that for long was the largest M-type with no detectionof hydration features in its spectrum, was recently discovered to have a weak 3micron band and thus it eventually was added to the group of hydratedasteroids. Its relatively high density in combination with the high radaralbedo, led to classify the asteroid as a metallic object, possibly a core of adifferentiated body, remnant of "hit-and-run" collisions. The detection ofhydration is, in principle, inconsistent with a pure metallic origin of thisbody. Here we consider the scenario that the hydration on its surface isexogenous and was delivered by hydrated impactors. We show that impactingasteroids that belong to families whose members have the 3 m band can deliverthe hydrated material to Psyche. We developed a collisional model with which wetest all the dark carbonaceous asteroid families, which contain hydratedmembers. We find that the major source of hydrated impactors is the family ofThemis, with a total implanted mass on Psyche to be of the order of 10^14 kg.However, the hydrated fraction could be only a few per cent of the implantedmass, as the water content in carbonaceous chondrite meteorites, the bestanalogue for the Themis asteroid family, is typically a few per cent of theirmass.
展开▼
