- Measurements from Rosetta’s Rosina instrument found that water on comet 67P /Churyumov-Gerasimenko contains about three times more deuterium – a heavy form of hydrogen – than water on Earth.
The discovery seems to overturn the theory that Earth got its water, and so its ability to harbour life, from water-bearing comets that slammed into the planet during its early history.
If this is confirmed, it's kinda huge.
Deuterated water requires more energy for phase changes to occur. The result they obtain could simply be a result of losing regular H2O to space at a slightly higher rate for billions of years.
Most of the heavier elements in our solar system condensed from the accretion disk into the rocky planets, nearer to the sun than the gaseous outer planets. That's why it's so strange to me that we'd find higher abundances of heavier water out in the Kuiper Belt or Oort Cloud than there presumably was/may be on asteroids, which are much more near to the sun. ...I love a good mystery!