Large impacts are fascinating. There’s the thriller-movie aspect of them, of course, spiced with enough reality to make them legitimately scary. But the physics of them is equally enthralling, and complex enough that it will be a rich field for scientists to study for years to come.
The good news for both these aspects is our Moon. Seriously! There are enough craters there for anyone to be happy studying them, and since the Moon is a giant lifeless chunk of rock, impacts there seem less urgently threatening.
I want to show you two craters on the Moon that are very different, and therefore very interesting.
First up, Copernicus. Or more accurately, a small part of this 90+ km (55 mile) wide impact feature: its central peaks.
[Click to enselenate.]
This image was taken by NASA’s wonderful Lunar Reconnassance Orbiter. Copernicus is a big crater, and easy to spot even with binoculars since it sits in a vast lava plain; the surrounding material is darkish grey, while the crater is far brighter. It’s also surrounded by a gorgeous system of rays: linear streaks caused by the collapsed plumes of material after the asteroid or comet smacked into the Moon to form the crater itself.
Copernicus has a series of mountains in its center, the tallest over a kilometer high. These weren’t created in tectonic events like on Earth, though! Giant impacts that cause big craters have weird physics. The pressure upon impact can be so high that the rock in the surface flows like a liquid. It splashes outward, then flows back in, surging upwards in the middle of the impact point. This video showing water dropping into various surfaces might help: