(New Scientist) If Earth got its water from space, it probably wasn't delivered by comet. That's according to the latest data from the European Space Agency's Rosetta spacecraft, which has been analysing the water content of comet 67P/Churyumov-Gerasimenko and found it doesn't match the water on Earth.
The question of where Earth got its water – whether from asteroids, comets or in some other way – is a subject of ongoing debate. So analysing comet 67P's water was one of Rosetta's main goals. The spacecraft's ROSINA instrument has been sniffing the vapour around the comet ever since reaching it in August.
Kathrin Altwegg of the University of Bern in Switzerland and her colleagues have now analysed 67P's water, by looking at the amount of deuterium, a heavy isotope of hydrogen, and comparing it with the amount of regular hydrogen.
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