Molecular oxygen and water at comet 67P/C-G
ESA's Rosetta spacecraft has made the first in situ detection of oxygen molecules (O2) outgassing from a comet. This surprising observation suggests they were incorporated into the comet during its formation.
More than 3000 samples, collected around the comet between September 2014 and March 2015, were analysed to identify the O2. High-resolution measurements allowed the team to distinguish O2 from other species such as sulphur and methanol. The strong correlation of molecular oxygen abundance with water vapour indicates a shared origin and release mechanism from the nucleus.