Given its distance from the Earth, it seems far-fetched to have an idea what comet 67P/Churyumov-Gerasimenko, the target comet of the Rosetta mission, smells like.

The Rosetta spacecraft of the European Space Agency has so far hinted scientists on how the comet looks like but it appears that the robotic space probe isn't just equipped to take images. It also has an instrument on board that can give scientists clues on what the comet smells like.

Rosetta has a device called Rosetta Orbiter Sensor for Ion and Neutral Analysis, or ROSINA, a mass spectrometer which can analyze the signature of gas from the comet's coma that envelops 67P/C-G as it draws closer to the sun.

With the aid of ROSINA, scientists can "smell" the comet and it appears that its whiff is not something that people want to be nearby. ROSINA principal investigator Kathrin Altwegg described the scent to be a mixture of rotten eggs, horse stable, formaldehyde and alcohol, which means that the comet stinks.

Altwegg said that the "perfume" of the comet is a bit strong due to the presence of hydrogen sulphide which gives off the odor of rotten eggs, ammonia that smells like horse stable and formaldehyde.

"This is mixed with the faint, bitter, almond-like aroma of hydrogen cyanide," Altwegg said. "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."

ROSINA detected molecules that include ammonia, formaldehyde, hydrogen cyanide, hydrogen sulphide and methane. The scientists behind ROSINA believed that only carbon dioxide and carbon monoxide, the most volatile molecules would be released as the icy surface of the comet begins to warm and the detection of the instrument of a number of different molecules at this stage when the comet is still more than 400 million kilometers from the Sun actually comes as a surprise.

ESA said that a detailed analysis of the chemical makeup of the comet and how this changes when the comet becomes more active will help scientists determine the composition of the comet.

The Rosetta mission was launched to orbit around 67P/C-G and land the Philae lander on its surface in a bid to learn more about the comet, which scientists hope could light on the history of the solar system. Rosetta's lander is scheduled for landing on the surface of the comet next month.

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