Was the Moon-Forming Protoplanet 'Theia' a Neighbor of Earth? (mps.mpg.de)
(Sunday November 23, 2025 @09:35PM (EditorDavid)
from the over-the-moon dept.)
- Reference: 0180188553
- News link: https://science.slashdot.org/story/25/11/23/2327252/was-the-moon-forming-protoplanet-theia-a-neighbor-of-earth
- Source link: https://www.mps.mpg.de/theia-and-earth-were-neighbors
Theia crashed into earth and formed the moon, the theory goes. But then where did Theia come from? The lead author on a new study says "The most convincing scenario is that most of the building blocks of Earth and Theia [1]originated in the inner Solar System . Earth and Theia are likely to have been neighbors."
Though Theia was completely destroyed in the collision, scientists from the Max Planck Institute for Solar System Research led a team that was able to measure the ratio of tell-tale isotopes in Earth and Moon rocks, [2] Euronews explains :
> The research team used rocks collected on Earth and samples brought back from the lunar surface by Apollo astronauts to examine their isotopes. These isotopes act like chemical fingerprints. Scientists already knew that Earth and Moon rocks are almost identical in their metal isotope ratios. That similarity, however, has made it hard to learn much about Theia, because it has been difficult to separate material from early Earth and [3]material from the impactor .
>
> The new research attempts a kind of planetary reverse engineering. By examining isotopes of iron, chromium, zirconium and molybdenum, the team modelled hundreds of possible scenarios for the early Earth and Theia, testing which combinations could produce the isotope signatures seen today. Because materials closer to the Sun formed under different temperatures and conditions than those further out, those isotopes exist in slightly different patterns in different regions of the Solar System.
>
> By comparing these patterns, researchers concluded that Theia most likely originated in the inner Solar System, even closer to the Sun than the early Earth.
The team published their findings in the journal Science . Its title? " [4]The Moon-forming impactor Theia originated from the inner Solar System ."
[1] https://www.mps.mpg.de/theia-and-earth-were-neighbors
[2] https://www.euronews.com/next/2025/11/23/long-lost-moon-forming-planet-formed-in-the-inner-solar-system-new-analysis-shows
[3] https://science.slashdot.org/story/14/06/06/0246206/evidence-of-protoplanet-found-on-moon
[4] https://www.science.org/doi/10.1126/science.ado0623
Though Theia was completely destroyed in the collision, scientists from the Max Planck Institute for Solar System Research led a team that was able to measure the ratio of tell-tale isotopes in Earth and Moon rocks, [2] Euronews explains :
> The research team used rocks collected on Earth and samples brought back from the lunar surface by Apollo astronauts to examine their isotopes. These isotopes act like chemical fingerprints. Scientists already knew that Earth and Moon rocks are almost identical in their metal isotope ratios. That similarity, however, has made it hard to learn much about Theia, because it has been difficult to separate material from early Earth and [3]material from the impactor .
>
> The new research attempts a kind of planetary reverse engineering. By examining isotopes of iron, chromium, zirconium and molybdenum, the team modelled hundreds of possible scenarios for the early Earth and Theia, testing which combinations could produce the isotope signatures seen today. Because materials closer to the Sun formed under different temperatures and conditions than those further out, those isotopes exist in slightly different patterns in different regions of the Solar System.
>
> By comparing these patterns, researchers concluded that Theia most likely originated in the inner Solar System, even closer to the Sun than the early Earth.
The team published their findings in the journal Science . Its title? " [4]The Moon-forming impactor Theia originated from the inner Solar System ."
[1] https://www.mps.mpg.de/theia-and-earth-were-neighbors
[2] https://www.euronews.com/next/2025/11/23/long-lost-moon-forming-planet-formed-in-the-inner-solar-system-new-analysis-shows
[3] https://science.slashdot.org/story/14/06/06/0246206/evidence-of-protoplanet-found-on-moon
[4] https://www.science.org/doi/10.1126/science.ado0623
The Earth may have moved into Theia's orbit (Score:2)
By interacting with millions of small bodies, Earth may have been losing orbital velocity and moved closer to Theia's orbit, setting up the collision.
Re: (Score:2)
I have thought about this in the last month. I find it interesting that the article seems to find isotopes that indicate that Theia was closer to the sun. From where did they find the isotopes I wonder? I suspect that two large masses were orbiting the sun at about the same distance, probably a similar orbit, and crashed into each other, creating our moon. The isotopes would have been mixed/mashed together though, it seems.
Re: (Score:1)
Oh boy this takes ancestor-guilt to the next level. Like shit, great great great great grandpa (of every race btw) held slaves .. that was bad.. but now you're telling me his great great great great^10 grandpa crashed into a whole fucking planet?
Re: The Earth may have moved into Theia's orbit (Score:2)
It would have been quite spectacular to watch the collision.
Re: (Score:2)
Could it have been a chunk of Alderaan that got thrown into our solar system when it was blown up? The documentary just says "a long time ago" but doesn't give an exact timeline.