Relative dating cratering distribution
That's how old geology on the Moon is -- it's almost inverted from Earth, where most of the geology that we can see in rocks around us happened in the last few hundred million years. Rocks returned by the Apollo astronauts that were thought to come from Nectaris are only 70 million years older than the dates we get for Imbrium. If Nectaris really is only 70 million years older than Imbrium, that tells a shocking story: that half of the Moon's biggest basins happened in a really short time, geologically speaking, an event that's sometimes called the "lunar cataclysm" or "late heavy bombardment." But what if the age for Nectaris is wrong?
When you're talking about things that happened nearly 4000 million years ago, 70 million is virtually an eyeblink. It could be; the compositions of lunar rocks read from orbit suggest that Apollo astronauts might just have been sampling Imbrium-related rocks over and over and over again, and that we don't actually know how old Nectaris is.
This is all part of the work geologists are doing right now -- sorting out the order of events in the history of the moon and other solid-surfaced worlds in the solar system, trying to understand our origin story.
Fascinating stuff, and I'll have more to say about this work in later posts.
Basin names are in caps if they are in caps on the map above, to help you locate them.
It lists the basins from oldest to youngest, based on crater counting -- basins with more, bigger craters on top of them are older.
I think that's appropriate because the Moon is where the study of planetary geology started, even before the Space Age.
The familiar face of the Moon contains dark splotches, the maria.
Arguably the most beautiful of the Moon's basins is Orientale, whose glory we really couldn't appreciate until the Space Age, because its eastern edge just peeks over the visible near side of the Moon.The big basins are old, so a lot has happened to them since they formed.