Jeffrey Andrews-Hanna

Just think of this as these are the gravity anomalies arising from the interior, arising from beneath the surface.

Now all those little craters go away, and we can see deeper structures.

And this is what we want to interpret.

There's one more thing that I'm going to show you that I'll present a lot in this talk, and that's something called gravity gradients, which is this bottom plot here.

This is basically just the slope of the gravity field.

It's highlighting areas where the gravity field is changing, as opposed to areas where it's all the same within a broad region.

Think of this as just like an image processing technique.

to bring out the transitions.

Put your photos in Photoshop and stretch the contrast to see the details better.

That's kind of what we're doing with these gravity gradients here.

All right, so looking at this gravity gradient map, looking at this in the GRAIL data, we see a lot of things that we knew about.

All of these circular bullseyes, those are impact basins.

And I'm going to talk about those a little bit later.

But when I looked at this data the first time, what I was most excited by was the things that I didn't know were there at all.

So here I'm highlighting, in the lighter tones, all these lines crisscrossing the moon.

These were a complete surprise, something we didn't know about, but were just jumping out very prominently in the gravity data.

Here's a blowup of one of these on the far side, this striking line arcing across the lunar surface.

When we look in topography data,

there's nothing there.

When we look in image data, there's nothing there.