Rosetta casts doubt on comets as Earth’s water providers
Comet 67P’s atmosphere contains a surprisingly high fraction of deuterium
![67P/Churyumov–Gerasimenko](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2014/12/ay_Comet_on_4_November_NavCam.jpg?fit=860%2C460&ssl=1)
GETTING FUZZY The basic chemistry of a comet’s thin, hazy atmosphere offers hints about how water got to Earth. It may not have been on the backs of comets like 67P/Churyumov–Gerasimenko.
NAVCAM/Rosetta/ESA (CC BY-SA IGO 3.0)