From infinity and beyond …

“Most hydrogen comes in a form in which its nucelus consists of a single proton, but there’s also an istope called deuterium that contains both a proton and a neutron. In the Earth’s oceans, only about 1.6 in every 5,000 water molecules contain deuterium, so if we’re looking for sources for our planet’s water, we need to find bodies that have a similar ratio. We’ve looked at six comets that originate in the Oort cloud (the distant-most bodies associated with the Sun), and they have ratios about double that found on Earth. That left enstatite chondrites, a type of meteorite, as the best match for Earth’s water.

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.”

Via ArsTechnica.