Jeffrey Andrews-Hanna

This is similar to what we think these long lines in the gravity data on the moon are, although those gravity anomalies we see on the moon are about 1,000 times larger than this.

So next time, if you're out driving or visiting Shiprock, look at that and picture it 1,000 times larger.

And that's what was forming on the early moon.

So now we know that there's this very ancient population of enormous dikes of solidified magma bodies in the lunar crust, older than the surface we see, older than the craters we see all over the surface.

So dating from the earliest evolution of the moon.

Why on earth is that the case?

Why on the moon is that the case?

Well, one thing that tells us is that the moon was expanding.

You had to make room for all that magma.

If the moon was expanding, its outermost shell, its outer crust, would crack and fracture, and that would make room for the magma to intrude.

So now we think that the earliest moon was expanding, and expanding by kilometers, by miles.

This is not a small amount.

How could that happen?

Well, so far, two theories have been proposed.

If you go back to earliest lunar evolution, where you've got a hot magma ocean over a cool interior, that's not stable.

As this interior warms up, it'll expand, as solids do when they warm up.

And that could cause the cracking and the dikes that we see.

It's also thought that as the moon's magma ocean evolved, in those last liquids as it was crystallizing, you put all of those radioactive heat-producing elements in there, and then they sunk deep into the interior.

put all those radioactive elements into the deep interior of the moon and it warms up the entire moon and the moon expands.

These are two completely different scenarios that would have the same effect that can both explain what we observe.