ESA reports that Comet 67P/Churyumov-Gerasimenko stinks. Analysis of data sent back by Rosetta shows that the comet is made up of water, carbon dioxide, and carbon monoxide. It also contains ammonia (NH3), methane (CH4), methanol (CH3OH), formaldehyde (CH2O), hydrogen sulphide (H2S), hydrogen cyanide (HCN), sulphur dioxide (SO2), and carbon disulphide (CS2).
The perfume of 67P/C-G is quite strong, with the odour of rotten eggs (hydrogen sulphide), horse stable (ammonia), and the pungent, suffocating odour of formaldehyde. This is mixed with the faint, bitter, almond-like aroma of hydrogen cyanide. Add some whiff of alcohol (methanol) to this mixture, paired with the vinegar-like aroma of sulphur dioxide and a hint of the sweet aromatic scent of carbon disulphide, and you arrive at the ‘perfume’ of our comet.