Theia

Yeah.

Perhaps, uh, there was a similar formation event to the event that formed our moon when, uh, Theia, the object size of Mars, clouted the Earth in the early history of the solar system, and eventually that coalesced to form the moon.

Uh, which by the way, I, I read a headline not very long ago that looks as though that formation of the moon from that debris cloud might have happened very, very quickly, and I can't remember how [chuckles] quickly it was, but it was-

Yeah.

Yeah, and it sort of harps back to a story from a few weeks ago about, uh, how they do think they have found continental-sized, um, anomalies, but, you know, deep in our crust that suggest-

Yes

... parts of Theia exist.

Might be parts of Theia, that's right.

The object that hit the young Earth was very large, not a small asteroid or a stray chunk of rock, but something roughly the size of a small planet, perhaps as large as the planet Mars.

Scientists have given this hypothetical impactor a name, Theia, after the Greek goddess who was the mother of Selene, the goddess of the moon.

The collision between Theia and the early Earth was enormous, one of the most violent events in the history of our planet, releasing more energy than anything we can easily imagine.

It sent molten rock into orbit around the Earth, a ring of superheated debris that glowed with the heat of the impact.

Over time, perhaps over the course of just a few years or decades, this material clumped together, cooling as it merged until it formed a solid body.

It cooled and became the Moon.

So our moon came from the Earth itself, at least in part.

It is made of material from both bodies, from the shattered remains of Theia and from the outer layers of the young Earth, blended together by the heat and violence of the collision.

That's weird that that could just happen.

A proto-planet called Theia.

Yeah, I saw that.

Ooh.

Cagan Denton and Robin Canup at the Southwest Research Institute with Erik Asphaug in Arizona in Astrophysical Journal Letters.

The canonical story is a Mars-sized body called Theia hitting the proto-Earth, throwing a disc of debris into orbit, and the moon slowly accreting out of it.

What this group added was something nobody had properly included, rock strength that changes with temperature.

Because previous simulations treated the rock as a fluid.

The collision directly produces a single intact satellite in about five hours.

Not always.

A hot young Theia under 60 million years old gives the immediate moon.

A cooler, older one gives the classical slow disc.

As this hellscape settled, gravity would do its work, and this cloud of hot material would pull together to form a completely new planet.

This is how we think the Moon formed billions of years ago, when Earth was hit by a Mars-sized object named Theia.

That impact was so powerful that it launched massive globs of molten material out into space, some of which fell back to Earth, and some of which came together to form the Moon.

But in this case, a direct collision with a similar-sized planet? Earth would be no more.

No, we got a real weird inside probably because we got hit by a Mars-shaped and sized thing early in our history, and it still- Wow ... makes it weird in there.

We've still got like hunks of Theia hanging out inside of our mantle.

That's very metaphorically resonant.

Is it? It is, yeah.