unknownskywalker:

Vesta likely cold and dark enough for ice

Though generally thought to be quite dry, roughly half of the giant asteroid Vesta’s poles are expected to be so cold and to receive so little sunlight that water ice could have survived there for billions of years.

Vesta, the second-most massive object in the asteroid belt between Mars and Jupiter, probably does not have any significant permanently shadowed craters where water ice could stay frozen on the surface all the time, not even in the roughly 300-mile-diameter (480-kilometer-diameter) crater near the south pole. This is because the asteroid is tilted on its axis at about 27 degrees.

As a result of its large tilt, Vesta has seasons, and every part of the surface is expected to see the sun at some point during Vesta’s year. This means the poles also see sunlight for long periods of time during the summer seasons, which isn’t so good for sustaining ice. So if water ice exists in those regions, it may be buried beneath a relatively deep layer of dry regolith.

The presence or absence of water ice on Vesta tells about the tiny world’s formation and evolution, its history of bombardment by comets and other objects, and its interaction with the space environment. Because similar processes are common to many other planetary bodies, learning more about these processes has fundamental implications for our understanding of the solar system as a whole.