Pittsburgh Alpha to Omega

But for an object long thought tectonically dead, the discovery of “recent” faulting on the lunar surface indicative of shrinkage is pretty surprising. It’s but the latest indication that “this isn’t your grandfather’s moon anymore,” says Michael Wargo, chief lunar scientist at NASA headquarters in Washington.

“When you look at the new information we’ve garnered with a number of different missions to the moon over the last year, we’re now talking about the moon in a completely different way,” he says. “It was thought to be dead and unchanging. And now you have this dynamism.”

The changes the LRO has uncovered may be taking place on geological time scales, he explains. But recent evidence that the moon has its own active, if spare, hydrological cycle has revealed a process that occurs on weekly and monthly time scales.

The moon’s newfound dynamism is “just unlike what folks were thinking of a year ago,” Dr. Wargo says.

“The moon is shrinking.  No, seriously.” by Pete Spotts, CSM 8-19-10

We see these sorts of features on many bodies in the solar system, including the Earth, where their origin is from tectonic plate motion. As the continental plates move past each other, friction allows the pressure to build up. There’s no such drift on the Moon — the surface is essentially one big piece — so something else must be causing it.

Shrinkage makes the most sense. The interior of the Moon is still warm from the leftover heat from its formation billions of years ago. Hundreds of kilometers of rock makes a pretty good insulator, so the Moon has cooled very slowly. As the interior cools, it shrinks, and the surface collapses down as well. Pressure builds, then snap! While a lot of these scarps are very long and dozens of meters in height, LRO’s sharp vision (it can see objects less than a meter in size!) can spot scarps that are only a kilometer or two in length and a few meters high. That sort of feature is not possible to see from Earth. They’re too small.

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Well, you have to put this into perspective: the Moon’s diameter is about 3475 kilometers. This shrinkage is only about 0.003% of that. In other words, you’d never, ever be able to see that by comparing the Moon’s diameter now as it was, say, a billion years ago. So we’re not in any danger of the Moon collapsing down into a tiny little ball!

What it does mean is that despite it being perhaps the most well-studied object in the sky, our Moon is still capable of surprising us. Not only that, but some of its secrets are actually rather big, but so well-hidden we need to study the Moon pretty carefully to uncover them. Happily, we’re doing just that. There’s not a scientist on the planet who doesn’t like surprises, especially when they’ve been sitting right there in the sky for us to find.

“The Moon is shrinking!” by Phil Plait, Discover‘s Bad Astronomy blog, 8-19-10

Still no word from NASA about Luna being artificial, covered with ancient monuments/devices and more recent Nazi/Nasty Alien bases, or about Luna’s interior being inhabited by beneficent robots guiding humanity’s development according to the Zeroth Law.  Instead, we’re asked to believe that it’s shrinking.

Please.

Have fun and cuídate.