NASA’s Dawn space craft has apparently spied hydrated minerals in craters on the surface of the asteroid Vesta – an indication that water has been there at some point in the past.
Vesta is one of the largest asteroids in the solar system and is widely thought to be the parent of many asteroids. Because of its mass it also attracts a fair few impacts as well – and it is these impacts that are likely to have brought water to Vesta.
Dawn didn’t detect water in the form of ice, but large concentrations of hydrogen atoms – most likely in the form of hydroxyl ions in minerals formed after collision with other water-bearing comets or asteroids – in a wide band around the asteroid’s equator.
Previously it was thought that Vesta could harbour some water ice in craters around its poles but this is now thought to be in error since Vesta has no permanently shadowed regions.