Was Earth’s Water Imported from Space?
“The composition of the Earth-Moon system indicates that the Moon probably formed from a collision between the proto-Earth and a Mars-sized body.
That collision was incredibly violent, and left the Earth hot enough that its atmosphere would primarily consist of vaporized silicate rock.
Once it solidified, those conditions would have left the planet very dry, with our current water largely delivered by smaller bodies that have impacted the Earth since.
So far, only a single type of meteorite has been found to have hydrogen and oxygen isotopes that matched those found in the oceans.
But researchers have now checked a comet derived from the Kuiper belt, and showed that it also is a good match for the Earth’s oceans…
Now, using the ESA’s Herschel observatory, researchers have gotten a good reading on the comet 103P/Hartley 2, which orbits near Jupiter but probably got its start in the Kuiper belt, just outside the orbit of Neptune.
And it turns out that the deuterium/hydrogen ratio is nearly an exact match for that in Earth’s oceans.
That means a large population of comets have just become candidates for seeding our planet with water.”