Bouncing on the Moon

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Nov. 12 2012 4:17 AM

Bouncing on the Moon

121111_BA_moon_bounce

Courtesy NASA/GSFC/Arizona State University.

Of all the amazing pictures returned from the moon by the Lunar Reconnaissance Orbiter—and I may include the Apollo landing sites among them—I think my favorites are the ones showing boulders that rolled down slopes.

Did I say rolled? I mean bounced!

This shot from LRO shows the floor of crater Shuckburgh E, an impact crater about 9 km (about 6 miles) across. The image shows a region about 655 meters (0.4 miles) across. The crater floor here is not level; it’s tilted up from left to right and also has contours. Boulders dislodged for some reason (a seismic event or a nearby impact) on the right have rolled down to the left … and some actually skipped along, bouncing and bounding as they did.

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The two biggest trails are dashed, indicating the boulders had a bit of a rollicking time before coming to rest. You can see both boulders at the left of the trails, where they came to a stop. Note that the sunlight is coming from the bottom of this picture, which can play tricks on perspective. I see the boulders looking almost like craters and the skidding trails they left like little mounds. If you flip the picture over it may look better to you.

As always, pictures like this are a strong reminder that even on the moon, where time stretches long and processes are slow, changes do occur. Maybe not often, and maybe not recently, but given enough time you have to think of the moon as a dynamic place.

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death from the Skies!