NASA | Recent Geological Activity on the Moon

[music] Tom Watters: Two years ago, we reported evidence that the moon is shrinking. Now, we’ve found evidence that the moon is actually being pulled apart–forming features called graben. So, the “shrinking moon” –it turns out, is not shrinking everywhere. Some places, the moon is actually expanding by a little bit. So, finding these young graben was a real surprise because we thought, well, all these lobate scarps are telling us the moon is shrinking, so what are these little, small graben that are telling us the moon is pulling apart–doing in this picture? How does this all fit together? All that’s related to how the moon has evolved–how the moon has lost heat. over its four-and-a-half billion year history. Most of the terrestrial planets, when they formed, were very hot, and they got so hot that they actually completely melted. When that happens, they will be in a general state of contraction because they’re still hot on the inside and cooling down, and as they cool, they want to shrink. Only the outer part of the moon melted, forming what is called a magma ocean, and in that model, the balance of stresses or forces that are acting on the moon would allow us to form both these small lobate scarps that show contraction, as well as these small graben that show the moon being pulled apart. One of the really, really exciting returns of the Lunar Reconnaissance Orbiter mission is that we’ve seen this now growing evidence of very young geoloic activity on the moon. Many, many people have felt that the moon is pretty much geologically dead, and what we’re finding is that that’s totally wrong, that the moon appears to be geologically active now. [music] [music, beeping] [beeping] [beeping, silence] [silence]