Jeffrey Andrews-Hanna

We don't know which one of these are correct, but they're telling us something about early lunar evolution that we're still trying to understand here.

All right, now I wanna change gears and talk about impact basins.

This is, again, this is something you can see with your eye.

Look up at the moon and those dark spots, as I said, they're volcanic planes, but if you look closely, a lot of them are pretty round, pretty darn circular.

And that's not a coincidence.

These volcanic planes formed inside of ancient impact basins.

This was actually noted in an early seminal paper, really pivotal paper published right here at the Lunar and Planetary Lab.

So a young grad student named Bill Hartman and his advisor, Gerard Kuiper, Kuiper, who this building is named after,

published a paper in 1962 about concentric structures around lunar impact basins.

This was really a defining paper that first described these rings around basins, around giant impact basins on the moon, and also made a very important discovery of a new impact basin that was unknown at the time.

See, on the edge of the moon, as we see it from Earth, there's an impact basin sitting right on the edge.

But we're looking at an edge on, which is not a good angle to see things from the Earth.

Now, we didn't have any orbiters to take pictures of this at this time, but Hartman and Kuiper did a really, really ingenious low-tech thing here.

They took a picture of the moon, and they projected it on a sphere.

Then all they had to do was just walk around to the side of that sphere, and they could get the side view of the moon that otherwise you'd only get from an orbiter.

I think this is brilliant.

Nowadays, we could write computer codes to do the same thing, but a slide projector and a basketball

Probably wasn't a basketball, but a sphere does the same thing.

When they did that and walked around to the side of their projected moon, they saw all of these arcuate structures surrounding a point just out of view.

And they said, that looks a lot like what we see in these things we're interpreting in impact basins on the near side.