Explanation:
From fifty kilometers above asteroid
Eros,
the surface inside one of its largest craters
appears covered with an unusual substance:
regolith.
The thickness and composition of
the surface
dust that is
regolith remains a topic of much research.
Much of the regolith on
433 Eros was probably created by numerous small
impacts during its long history.
In this representative-color view taken by the
robot spacecraft NEAR-SHOEMAKER that
orbited Eros in 2000 and 2001, brown areas indicate
regolith that has been chemically altered by exposure to the
solar wind during
micrometeorite impacts.
White areas are thought to have undergone relatively less exposure.
The boulders visible
inside the crater appear brown,
indicating either that they are old enough to have a
surface itself tanned by the
solar wind, or that they have somehow become
covered with some dark surface
dust.
This July, NASA's
Dawn spacecraft
will orbit giant main belt asteroid Vesta.
