This finding ties in with the revelation of hydrogen on Vesta, because the likeliest explanation for the indentations on the surface is that hydrogen, which is likely bound up in minerals there, is released in the form of water vapor when the material is heated up by impacts.

MSN: Surprisingly, giant asteroid Vesta covered in hydrogen

Hydrogen was indeed found, but it is still unclear whether it is in the form of ice, or of some other hydrogen-containing compound, such as hydrated minerals that have water bound chemically into their crystal structures.

ECONOMIST: Creative destruction