This is an image of the surface of Mercury.
Click on image for full size
NASA
Early Cratering of the Planets
When we look at images of many of the planets, we see all sorts of
circular craters on the planet surfaces. Most of these craters
were probably formed when the solar system was still very young.
Once the early solar system had planets about the size of the planets
today, there were still probably a lot of smaller bodies around, too.
The
gravity of the large planets would attract nearby smaller bodies,
which would hit the planets and leave a crater on the planet's
surface.
Craters on the surfaces of the inner planets are up to 4 billion
years old, and some craters seem to have been made by objects
up to 200 km across!
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