|Where are the craters on asteroid Itokawa?
Missing -- unexpectedly.
The Japanese robot
Earth-crossing asteroid in 2005 and
returned pictures showing a surface unlike any other
body yet photographed -- a surface possibly devoid of
The leading hypothesis 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 not form so easily -- or be filled in whenever the
asteroid gets jiggled by a passing planet or struck by a massive meteor.
Recent Earth-based observations of asteroid Itokawa have shown that one part
of the interior even has a
higher average interior density than the other part, another
The Hayabusa mission returned soil samples from
which are also giving clues the ancient history of the
and our entire Solar System.
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