A space-age mystery to celebrate Apollo's anniversary

A space-age mystery to celebrate Apollo's anniversary

A space-age mystery to celebrate Apollo's anniversary

Bad Astronomy
The entire universe in blog form
July 21 2011 11:30 AM

A space-age mystery to celebrate Apollo's anniversary

Last night, at 02:56 UTC, it was the 42nd anniversary of humans putting a bootprint on another world. Before Apollo 11 touched down on the Moon, though, NASA and the USSR sent a fleet of unmanned probes there. Since that time we've sent many more, including the Lunar Reconnaissance Orbiter, one of my favorite spacecraft of all time. It takes amazing high-res images of the Moon... and to celebrate today's anniversary, they released this mysterious picture:

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

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This image is about 400 meters across, and shows an impact site with two lobes of material laid down to the sides. This butterfly-shape is a clear indication of a low-angle impact; it's seen on many bodies in the solar system including the Moon, Mars, and even Earth (though the physics of exactly how the bi-lobed patterns form is still not well understood). Features like this are very rare... but it's known that when a satellite orbit decays, it will impact at a low angle.

As the LRO site notes, in October 1967, the Lunar Orbiter 2 spacecraft impacted the lunar surface, possibly very near this spot. Could this be the final resting ground of an early NASA robotic explorer? It's hard to say. When something hits hard enough to excavate material, it's common to see ejected junk of different brightnesses, and here we see the dark patterns overlaid on a brighter surface. If that's the impact area, though, the size of the impact looks too big for the mass and speed of the probe. Maybe it coincidentally hit a brighter area, but that stretches credulity, given the darker area all around.

So what happened here? The folks at LRO are planning follow-up observations to see if they can get pictures at a different Sun illumination angle, which will make any crater easier to spot. That might clear things up.

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Or it might not. The Moon is the nearest astronomical object in the heavens by far, but it also has 38 million square kilometers of surface to explore! That's four times the size of the Unites States... and LRO sees it at a resolution of roughly a half a meter. That's a whole lot of pixels, and a whole lot of landscape in which to hide fun little mysteries. I hope there are many, many more.



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