Explanation:
Where are the craters on asteroid Itokawa? No one knows.
The Japanese robot
probe Hayabusa recently
approached the
Earth-crossing asteroid and is
returning pictures showing a surface unlike any other
Solar System
body yet photographed -- a surface possibly devoid of
craters.
One possibility for the lack of
common circular indentations is that
asteroid Itokawa is a
rubble pile -- a bunch of rocks and ice chunks only loosely held together
by a small amount of gravity.
If so, craters might be filled in whenever the
asteroid gets jiggled by a passing planet --
Earth in this case.
Alternatively, surface particles may become
electrically charged by the Sun, levitate in the
microgravity field,
and move to fill in craters.
Over the weekend,
Hayabusa lowered itself to the surface of the
strange asteroid in an
effort to study the unusual body and collect surface
samples that could be returned to Earth in 2007.
