This is the planet that smashed into Earth and created the Moon and pieces of it are buried deep below us

Originally published at: This is the planet that smashed into Earth and created the Moon and pieces of it are buried deep below us | Boing Boing


Different than the artist’s rendering I saw three decades ago, but OK.


Centrifugal Force:

Blackplanet GIFs - Get the best gif on GIFER


Alternative artist rendition:


A geophysicist explained to me once that part of what makes thinking about the Earth’s interior difficult is that it is indeed convecting, it’s only done that, like, four times over since its formation. So one has to do non-equilibrium statistical mechanics. I’m not surprised that Theia’s signatures are still visible.


These structures are so massive that if you put them on Earth’s surface, they would make a layer roughly 60 miles (100 km) thick around the entire planet.

for reference, mt everest is about five and a half miles in height, and space starts at around 50 miles.


Who exactly called the smaller planet Theia? They just made that up. It’s not like there was some primordial goo being looking up to the sky and thinking “that planet Theia sure looks like its getting really close.”

1 Like

The Theians? After all, those white super-science Atlantians had to come from somewhere. /s


Isn’t the theory that the same collision which created the moon also knocked Earth into its 23.5-degree tilt?

It’s kind of weird to think the moon, the tides, and the seasons are all the result of a random space encounter 4.5 billion years ago.


Somebody made up every name for the things we’ve discovered, both ones that still exist and in the past. This one came from Halliday (2000), with credit to R. Wieler, after the titan who was mother of the Moon. It’s become a fairly standard way to refer to it ever since.


Uatu passed along this information, but don’t tell anyone. He’s already in enough trouble for violating his oath to only observe.


Apparently, scientist just theiarized that was what the little planet was called.



and us, maybe. i’d wonder if life would have started here if not for the very specific chain of cosmic events that played out


I was reading something about the difference between us and Mars, in terms of keeping our Atmosphere for so long, and how it was partly due to how much more iron we have in our core. I wonder how much of that iron started in Theia?


Yes, the Earth has been able to protect the atmosphere from erosion by the Solar Wind by having a powerful magnetosphere which deflects charged particles from the Sun that would otherwise help blow gases into space. The field is generated by the slow churn of the liquid iron/nickel Outer Core driven by heat escaping from the solid Inner Core.

As for how much iron Theia might have contributed to the Earth - I’d estimate, not a lot, Venus which is almost the same size as Earth has a density of 5.24 g/cm³ whilst that for Earth is 5.51 g/cm³.

Though there are some weirdnesses - Venus doesn’t have a global magnetic field of any size which suggests its Outer Core isn’t convecting. We really don’t know why yet. And that lack of magnetic field means Venus’s atmosphere is being blown into space and can be detected by space probes.


The deep Mantle is pretty much the frontier of geology right now. Seismic tomography and big data techniques are making it possible to image right down to the Core/Mantle boundary about 2900km down. This is really exciting (honest) as it might finally answer a couple of really big questions:

  1. What happens to Oceanic Crust when it is subducted back into the Mantle? Down to about 600km they can be traced by earthquakes, but beyond that, the plate becomes plastic and doesn’t fracture. It’s not clear what happens then - do they entirely dissolve back into the Mantle, do they keep diving down until they hit the much denser Core boundary, or do they ‘float’ in ‘plate graveyards’ at some intermediate distance?

  2. Where do Mantle Plumes originate? The favourite theory is that they rise from at, or just above the Core/Mantle boundary, but they are remarkably elusive in the seismic data - a few plumes are clearly demarcated, others just don’t seem to be visible - yet they produce large amounts of magma - what the hell is going on?


I’d never really put these thoughts together:

  • “Venus has no magnetic field”,
  • “Magnetic fields protect the atmosphere from being blown into space”, and
  • “At the surface, Venus’s atmosphere is 90 times denser than Earth’s”.

There’s some seriously interesting stuff going on there.


The Theians of course. They never left.

Donald Trump Animation GIF by Richie Brown


Seismic signals are badly confounded by the Beast Shouting Love.

Anyway, whatever CODE DEEP SEVEN are up to down there, I am in favour of leaving them to it and respecting their privacy.