spacetoday.net: Rosetta data raises questions about source of Earth's water

Rosetta data raises questions about source of Earth's water

Posted: Sat, Dec 13, 2014, 10:47 AM ET (1547 GMT)
Rosetta spacecraft illustration (ESA)

Data obtained by ESA's Rosetta comet mission have raised doubts that comets like the one being studied by the spacecraft are the source of the Earth's water. Rosetta measured the ratio of deuterium to hydrogen in 67P/Churyumovâ€“Gerasimenko, a Jupiter-family comet like those scientists speculated delivered water to the Earth through impacts early in the planet's history. However, the D-to-H ratio measured by Rosetta was higher than that of the water on Earth, and more like comets in the more distant Oort Cloud. Scientists working on the Rosetta mission said asteroids, which contain water with D-to-H ratios like that of the Earth, may be a more likely source of the Earth's water.