Scientists tracking a comet within the solar system have declared that it has the unmistakeable smell of horse urine – along with a host of other mostly unpleasant odours.
An instrument aboard the probe Rosetta, which rendezvoused with Comet 67P/Churyumov-Gerasimenko in August, has used its two mass spectrometers to, as scientists put it, “sniff the fumes”.
The European Space Agency science team which runs the Rosetta Orbiter Sensor for Ion and Neutral Analysis, known as ROSINA, said that the comet, which is currently 400 kilometres from the sun, is releasing a surprisingly rich array of chemicals.
ROSINA in September detected water, carbon monoxide, carbon dioxide, ammonia, methane and methanol.
Since then, it has picked up formaldehyde, hydrogen sulphide, hydrogen cyanide, sulphur dioxide and carbon disulphide.
Rosetta detected the signature of these chemicals as it tracked alongside the comet, just 10km from the comet’s centre.
Kathrin Altwegg, principal investigator for ROSINA, put it this way on the European Space Agency website: “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.”
While this is unlikely to be a particularly attractive perfume, the agency points out that the density of these molecules is very low, and that the main part of the nebulous envelope around the nucleus of a comet is water and carbon dioxide, mixed with carbon monoxide.
The chemicals released by the comet are expected to grow more diverse as the comet gets close to the sun.
Space agency staff have identified a suitable landing spot on the comet and will launch Rosetta’s lander, Philae, on November 12.