spaceSpace and Physics

What Does A Comet Smell Like?

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Lisa Winter

Guest Author

21 What Does A Comet Smell Like?

Space smells like hot metal and seared steak, while the center of the Milky Way tastes like raspberries and smells like rum. Unfortunately, some recognizable odors in space are not even remotely appetizing. According to researchers with the European Space Agency’s Rosetta spacecraft, the comet it is orbiting smells completely repugnant.

Rosetta has been analyzing the properties of comet 67p/Churyumov-Gerasimenko since the two met up in August. Comet 67p/C-G is headed toward the Sun and the increasing temperatures are causing materials to be shed off, which can then be analyzed using the Rosetta Orbiter Sensor for Ion and Neutral Analysis (ROSINA) via two mass spectrometers.


The first results on the comet’s gases came out on September 11, when the team revealed that water (H2O), carbon monoxide (CO), carbon dioxide (CO2), ammonia (NH3), methane (CH4), and methanol (CH3OH) were all present. 

The most recent results indicate that ROSINA was also able to sniff out these additions to 67p/C-G’s musk: formaldehyde (CH2O), hydrogen sulphide (H2S), hydrogen cyanide (HCN), sulphur dioxide (SO2), carbon disulphide (CS2). These aren’t ingredients you should expect to see in your favorite bottle of perfume, though they do exist in relatively low quantities. Water, carbon dioxide, and carbon monoxide are the overwhelming majority of material being kicked off and making up the comet’s coma.

ROSINA principal investigator Kathrin Altwegg did not mince words when describing how these gasses smell when added together:

“The perfume of 67P/C-G is quite strong, with the odor of rotten eggs (hydrogen sulphide), horse stable (ammonia), and the pungent, suffocating odor 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.”

Rosetta and 67P/C-G are currently over 463 million kilometers away from the Sun, between the orbits of Mars and Jupiter. As the comet continues to travel toward the inner solar system, the gases are going to become increasingly active, inundating poor Rosetta with this inescapable stench. Rosetta’s lander, Phillae, will be making direct contact with the comet on November 12 and will take samples to determine the comet’s composition directly from the nucleus.


Comet 67P/C-G comes from the Kuiper Belt. Understanding the composition of comets like this can be compared to comets that come from elsewhere, such as the Oort cloud. In addition to giving clues about the possible smell of these objects, the chemical composition could reveal secrets from when our solar system was forming and might even indicate how life emerged.

[Hat tip: i09]


spaceSpace and Physics
  • tag
  • Comet 67p/Churyumov-Gerasimenko,

  • Rosetta,


  • mass spectrometry,

  • odor