Fresh Moon Crater
© NASA/GSFC/Arizona State University

With all the hoopla about the Moon having or not having water, let's not forget our satellite's best-known features: its craters.

Although typically a sign of an ancient, unchanged landscape, a new crater on the Moon reminds us that we still live in an intergalactic shooting gallery.

The new crater was announced last week by the Lunar Science Institute at NASA Ames. The impact occurred sometime between an image of the region taken by the Apollo program in 1971 and an image recently taken by the Lunar Reconnaissance Orbiter (LRO).

The LRO is a spacecraft that is taking large amounts of data on the Moon's terrain and mineralogy, as well as taking those neat pictures of the Apollo landers and astronaut footsteps.

The crater itself is ten meters across, suggesting to me that the impactor was roughly a meter in size. Chunks of rock that size might hit the Earth several times a year, causing a stir in the local media or falling harmlessly and unnoticed. On the Moon however, it makes a bright crater, spewing forth lighter colored rock over the dark basalt surface.

Untouched by the powerful erosion processes as can be found on Earth, that crater will be visible for millions, if not billions of years to come, provided it doesn't get "erased" by another impactor.

By searching for more such craters, comparing archival photographs to LRO's stunning images, lunar scientists can get a better handle on the current impact rate in our neighborhood of the solar system. Not only will that give us an idea of how many rocks are headed for Earth, but an idea of what chances a future human base might have of running into trouble.

The Moon is smaller than the Earth, and therefore has less of a gravitational pull on incoming rocks. However, it lacks an atmosphere that would burn up smaller impactors as is the case on Earth. I can see it now, an astronaut gets bonked on the space helmet and turns around to blame his or her colleague for playing around! So maybe it is best that we know the impact rate as well as we can.