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From the massive craters on the
near side of the moon scientists
have assumed that the early solar
system experienced a barrage of
giant asteroid impacts during a
period called the Late Heavy
Bombardment about 4 billion
years ago. But according to
simulations by MIT researchers
moons' near side craters may not
represent the intensity of the
Late Heavy Bombardment. In fact
the size of such incoming
asteroids may have been over-
estimated for all these years.
A simulation of of an asteroid
impact on the moon's near side
shows the first 90 minutes after
the initial impact. The simulated
asteroid is 30 kilometers wide
and makes impact at 10 kilometers
per second creating a relatively
large crater on the nearside.
In contrast a simulation of the
impact on the moon's far side
by the same asteroid creates a
much smaller crater than on the
near side. The difference in
crater size is due to hotter
temperatures and a thinner crust
on the near side of the moon.
Conditions that make it easier
for relatively small asteroids
to make a bigger impact.
What does this all mean?
Researchers say that craters on
the far side of the moon may
give a more accurate picture of
the Late Heavy Bombardment.
Instead of a hail storm of giant
asteroids, much smaller asteroids
may have bombarded the early
solar system.