What do you think a comet smells like?

We’ve been giving out Rosetta smelly comet postcards in the European Parliament and asking people what they think a comet smells like. We’ve added the responses to our list from the EuroScience Open Forum (ESOF) 2016 in Manchester, back in July.

The answers are wide and varied:

Dusty hi-fi. Madrid Airport. Face powder. Hospitals. Almond biscuits. Toilet block freshners. Worked metal and fried meat. Old Chanel. Carbon. The Jorvik Viking Centre. Cut grass. Talcum powder. A car air freshener that’s been run over by a truck. Chalky. Stables. Sandalwood. Plasticine. Musty. Dodgy aftershave. Toilet paper. Patchouli. The London Dungeon. Dust. Burnt essence. Indian Ashram. Toilet cleaner. Coal. Old felt toy. Incense. Earthy. Cat litter tray. Air-bag packaging. Hand wipes. Horse poo. Old-fashioned soap. Rotten animals. Playdoh…

The smell recreates the chemical profile of comet 67P/Churyumov-Gerasimenko, as measured by the mass spectrometer instruments on the Rosetta orbiter and Philae lander. The chemical composition of the comet mostly:

• H2O (water)
• CO (carbon monoxide)
• CO2 (carbon dioxide)
• H2S (hydrogen sulphide)
• NH3 (ammonia)
• CH2O (formaldehyde)
• CH3OH (methanol)
• SO2 (sulphur dioxide)

Rosetta has discovered many other rare molecules in the comet, including amino acids that are the building blocks of proteins and all life on Earth.