The Rosetta Orbiter, which is orbiting Comet 67P/C-G, has recently reported back on what the fumes coming off of the comet smell like--and it's not good. Rosetta is using its 'mass spectrometers' to 'sniff' what the ESA is calling the comet's 'perfume.' Some of the latest substances detected by Rosetta include formaldehyde, hydrogen sulphide, hydrogen cyanide, sulphur dioxide and carbon disulphide.
According to mission officials, the mixture isn't something you'd want to smell. "The perfume of 67P/C-G is quite strong, with the odour of rotten eggs, horse stable, 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 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."
Scientists have also pointed out though that since the majority of the comet is made of water (or ice, more precisely) the concentration of these odorous chemical is relatively low and might not be too bad if you were standing on its surface and had a spacesuit that allowed you to smell space gas.
Though the comet is still some 400 million miles from the Sun, gaseous activity is already at a decent level and is expected to rise as the comet nears our solar system's star. Researchers are eager for the comet to become more active, because that activity will allow them to better understand the makeup of 67P/C-G, especially in comparison to what scientists know about the composition of other comets in our solar system.
In particular, scientists are eager to compare the difference between comets that originate from the Kuiper Belt (like 67P/C-G) with those from the Oort Cloud (the mysterious region beyond Pluto that contains most of the comets in our solar system). Comet Siding Spring, which just passed withing 90,000 miles of Mars, came from the Oort Cloud, and scientists feel that by examining comets they can learn much about the origins of our solar system and others like it.
