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Astronomy Picture of the Day
A Spherule from the Earth's Moon
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#100683
by
[z]Barbara Harris
@
21.05.2007 00:00
- nach oben -
A Spherule from the Earth's Moon
Explanation: How did this spherule come to be on the Moon? When a
meteorite
strikes the
Moon
, the
energy of the impact
melts some of the
splattering rock
, a fraction of which might cool into tiny
glass beads
. Many of these
glass beads
were present in
lunar soil samples
returned to Earth by the
Apollo missions
.
Pictured above
is one such glass
spherule
that measures only a quarter of a
millimeter
across. This
spherule
is particularly interesting because it has been victim to an even smaller impact. A miniature
crater
is visible on the upper left, surrounded by a fragmented area caused by the
shockwaves
of the small impact. By
dating
many of these
impacts
,
astronomers can estimate
the history of
cratering
on our Moon.
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