730 LCROSS - Crater Sizes -Transcript
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 LCROSS - Lunar CRater Observation and Sensing Spacecraft
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Lunar CRater Observation and Sensing Satellite (LCROSS)

Comparing Lunar Crater Sizes

When LCROSS’s Centaur upper stage impacts the Moon, it will create an impact crater. This is nothing new, the Moon’s surface is covered with billions of craters. This process of crater formation has been going on for billions of years, and is still going on today as pieces of rock and ice continue to crash into the Moon.

Scientists estimate that the crater that will be created by LCROSS’s impactor will be about 20 to 25 meters in diameter, or about 1/3 the size of a football field. How does this compare to other craters on the Moon?

Through a telescope, one of the most eye-catching of the lunar craters is Copernicus. This beautiful example is 93 kilometers in diameter, bigger than a large city. Copernicus shows lots of fine detail that helps us understand how such craters form. But as spectacular as Copernicus is, it is far from the largest impact feature on the Moon.

The largest craters, called impact basins, are big enough to be seen even without a telescope. Look up at the full Moon and se if you can identify some of these impact basins. The central areas of some like the Iridium Basin and the Crisium Basin show up as dark areas because of ancient lava flows that flooded their floors. The Crisium Basin is over 600 kilometers in diameter, and the Iridium basin is 1,200 kilometers across.

The largest impact basin is almost entirely on the far side of the Moon. The Aitken Basin is 2,500 kilometers across. Compared to this, the LCROSS crater sounds tiny, and it is.

But our view of the size of the LCROSS crater depends on what we compare it to. Here you see East Crater near the Apollo 11 landing site. At 20 to 25 meters in diameter, this is about the size we expect the LCROSS crater to be. Look closely, and you can see many much smaller craters on the side of East Crater. But even these craters are huge compared to the smallest craters that we have found.

This is a bead of lunar glass only ¼ of a millimeter in diameter. It was formed in the heat and pressure that created one of the lunar craters. But look closely at this bead. While it was lying on the Moon’s surface, it got hit by a tiny micro-meteoroid. You can see an impact crater, only about 0.1 millimeter in diameter, which was formed on this bead.

Lunar craters come in a huge range of sizes. How will the size of the LCROSS crater compare with other craters on the Moon? Its expected 25 meter diameter is 250,000 times larger than the 0.1 millimeter diameter of one of the smallest craters we have seen. And it is 100,000 times smaller than the 2,500 kilometer diameter of the Aitken Basin.

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Visit the NASA Mission Site @ http://www.nasa.gov/lcross

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Editor: Brian Day
NASA Official: Daniel Andrews
Last Updated: May 2008