Jeffrey Andrews-Hanna

This is something contained entirely within the interior of the Moon that we didn't know about before GRAIL.

Here's another one of these on the far side.

Again, about 300 kilometers long, it's about 200 miles long, linear anomaly.

Again, in topography and image data and every other data set we look at,

Nothing.

This is a subsurface anomaly that we discovered with GRAIL.

So what are all these lines?

Why are all these lines crisscrossing the moon?

Well, when we looked at the actual gravity anomalies, we see a big positive gravity anomaly going across these lines.

That tells us there's excess mass.

There's a mass excess in the subsurface.

From geology, the one thing we know of that can do that would be a long plane of dense rock, something like a dense igneous rock.

That's what we would describe as a dike.

where magma intrudes into the crust along a plane and then solidifies, and that solidified magma is more dense than the typical rocks around it.

So that shows up strongly in the gravity data.

So here, not too far away, we've got Shiprock in New Mexico.

We drive past this on our way to Colorado.

Really dramatic features if you haven't seen them, but what Shiprock is is an ancient eroded volcano where this is

The core of the volcano and this long, linear ridge is a dike.

That dike formed deep beneath the surface, but because of erosion, we can see it sticking up today as a ridge.