Explanation:
Manicouagan Crater in northern Canada is one of the oldest
impact craters known.
Formed about 200 million years ago, the present day terrain supports
a 70-kilometer diameter
hydroelectric
reservoir in the telltale form of an
annular lake.
The crater itself has been worn away by the passing
of
glaciers and other erosional processes.
Still, the hard
rock at the impact site has preserved much of the
complex impact structure
and so allows scientists a leading case to help understand
large impact features on
Earth and
other Solar System bodies.
Also visible above is the vertical fin of the
Space Shuttle Columbia
from which the picture was taken in 1983.
