Jeffrey Andrews-Hanna

What I can then do is take that Bouguer gravity, this is topography on the left, and I'm taking that gravity to model what the crust-mantle interface would be.

So if we've got a low density crust on top of a high density mantle, and that's the source of the gravity anomalies, we can use the gravity anomalies to figure out what that boundary between the crust and the mantle is doing.

And here's a cross section through that.

What we see is that, well, within the center of the basin, the mantle's been lifted upwards, and the crust is thinner.

Well, that's what we expect in a big impact.

It should excavate out the crust.

When we look outside the central region, in the surface, we see these wiggles that correspond to those scarps that you can see in the images.

In the subsurface, we see the same wiggles and they're parallel to what's going on at the surface, but shifted over by a little bit.

This is telling us that there are indeed faults originating at those rings and that those faults go all the way through the lunar crust down into the lunar mantle.

Now, while I've been using gravity data to try to understand the structure of the basin, a colleague of mine, Brandon Johnson at Brown, has been using models to investigate the impact process.

So this is an animation of an impact as could produce the oriental basin.

This is the asteroid right here.

I'll point to this.

That's about to strike the moon.

And as we run this forward in time, you see this incredibly dynamic process where the crust and mantle are excavated.

Material splashes out into the outer regions.

You see oscillations where the mantle is oscillating up and down by hundreds of kilometers, or at least in excess of 100 kilometers.

An incredibly dynamic impact event with just amazing consequences.

Here you can see that uplift of the mantle and that thinning of the crust that we're seeing from the GRAIL gravity data.

But when Brandon looks at his models up close,