Exploratour - Evolution of the Solar System

For many planets, such as Mercury which is shown here, pictures show that there are lots of craters. The craters were formed early in the history of the planet. Because there are so many craters, scientists can tell that not much has changed on the surface of Mercury since the beginning of the planets' history.

Craters on the surface are clues to the activity of a planet, sort of like a footprint left in the snow overnight. If you left a footprint in the snow one night and then went to bed, in the morning when you went to look at the footprint, a couple of things might happened. If snow continued to fall through the night, then by morning the footprint is gone. If snow doesn't fall after the footprint is made, then in the morning the footprint remains in the snow.

So it is with craters. If wind, rain, volcanoes, and other activity on the surface of the planet are at work after the creation of the craters, then they erase the craters. Thus scientists can often trace a planets age by counting the amount and size of the craters on the surface.



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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA