Jeffrey Andrews-Hanna

But here in this proselytum region, again, we've got this crazy square-type pattern.

If we look at a few of these border structures in detail and look at cross-section through those, so this is the gravity data.

This is a cross-section through the structure as we model it based on the gravity data.

And those long linear segments we see bordering this region, if we look at a cross-section through those, what we see is that the crust has gotten thinner, the mantle's been lifted up, and the lava, the mare there, has become thicker.

This cross section here, well, if we just look at the crustal part, that thin crust in a narrow zone, that's what you expect when the crust is rifting, when you've got extension stretching and thinning out the crust, and then these volcanic eruptions then flooded the whole area in basalt and made these dark maria that we see today.

And that's what we're interpreting this as.

This is an image of the East African Rift, one of the most famous rift valleys on the Earth.

That is what we think is happening on the moon.

Ancient, very ancient rifting was stretching apart the crust, causing these enormous tectonic patterns and this giant square pattern.

And then the whole region got flooded with lava.

Now, this is a topographic map of the region around the East African Rift Valley called the Afar Triple Junction, the Red Sea, the Gulf of Aden, the East African Rift Valley here.

As a geophysicist, as a theoretician, I have the privilege of being able to just take this whole area and flood the whole continent with lava.

It's something that we can do in theory, but not in practice.

So when I do that, I can then model the gravity field.

This is what I would expect this area to look like if I were to flood it with lava and gravity data.

And you see a structure, this sort of right angle pattern with this strong gravity gradient anomalies is very much what we're seeing in the gravity data.

So it seems to be a reasonable interpretation here.

Now, just to try to give a visualization of what this might have looked like, I've tried to combine the grail gravity data with images.

They wouldn't have really looked like this, but it's a fun way to visualize it.

So this is all data, but merging the grail gravity with images of what these rift valleys would look like crossing the moon.