image credit: NASA, JPL, USGS; image source; larger image

Impact Cratering

The Galileo spacecraft captured this image as it passed by the moon on its way to Jupiter. See the smooth dark areas? They were created three to four billion years ago when large volcanoes erupted and lava filled in the low-lying regions. Most of the smooth dark areas are round--these started off as enormous craters. Later, volcanoes erupted and filled them in, producing "impact basins." To find out more about how impact basins were formed, visit Impact Cratering.

In the right half of the image above, look at the region close to the edge of the shadow, where the craters stand out most clearly (that's because the angle of the sun is low). Note how the whitish regions of the moon are almost completely filled with craters, whereas the smooth, dark areas have very few. For a possible explanation, called the "late heavy bombardment," visit NASA's The Solar System's Big Bang.

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Impact Craters

For an activity on the formation of impact craters, try this NASA activity. Be sure to do this activity with an adult.

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image credit: NASA; image source; larger image

The Apollo Program: Apollo 15

You're looking at the vicinity of NASA's Apollo 15 landing site, located almost in the center of the image, on the lava surface at the eastern edge of Mare Imbrium (click for a lunar map to find it). Naturally a smooth impact basin would be the best place for the lunar lander to put down. You can also see part of the Apennine mountain range in the image above.

The Apollo Program's mission was to explore and map the moon. To learn more about Apollo 15, see The Apollo Program: Apollo 15.

Do you see the squiggly line running up and down in the middle of the image? It's actually a trench called the Hadley Rille. Here is a video of Apollo 15 landing, with the Hadley Rille in the background. On a lava-filled basin, and with a mountain range and a rille so close, the astronauts could explore plenty of lunar geology.

Surface Properties of the Moon

Check out Surface Properties of the Moon for more on the moon's craters and surface material.