Now we've gotten closer than ever to a comet in space, we can start answering serous scientific questions, like... err, what such a thing smells like?

Since August, Rosetta's two mass spectrometers have been sniffing out what 67P/Churyumov-Gerasimenko smells of. Scientifically speaking, that means detecting the most volatile molecules released via sublimation. But really, that means working out what it smells like. So far, Rosetta has sniffed out the following

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  • Water (H2O)
  • Carbon monoxide (CO)
  • Carbon dioxide (CO2)
  • Ammonia (NH3)
  • Methane (CH4)
  • Methanol (CH3OH)
  • Formaldehyde (CH2O)
  • Hydrogen sulphide (H2S)
  • Hydrogen cyanide (HCN)
  • Sulphur dioxide (SO2)
  • Carbon disulphide (CS2)

What does that smell like in practice? According to the European Space Agency: "If you could smell the comet, you would probably wish that you hadn't ." If that doesn't satisfy your curiosity, Kathrin Altwegg, a lead scientist on the project, explains:

"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."

Maybe Rosetta should've taken some air freshener, too. [ESA]