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Young Voices for the Planet DVD in our online store includes 8 films where students speak out and take action on climate change.
This is an image of the surface of Mercury.
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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 planetesimals and debri around, too. The gravity of the large planets would attract nearby planetesimals, 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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The Summer 2010 issue of The Earth Scientist, available in our online store, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.

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