Satellite ‘sniffs’ hurtling comet to find out what it smells like

What does a comet smell like? Pretty bad, according to a satellite racing towards the sun alongside the comet Churyumov-Gerasimenko.

It is an eau du cologne to forget, with a combination of horse pee, rotten eggs and pungent vinegar amongst other things.

The "sniffing" is being done by the Rosina (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) experiment on board the Rosetta satellite. Last August the satellite ended a 10-year race to catch up with the comet and fly along side it to watch what happens when it forms a tail and starts to sizzle as it gets closer to the sun.

The comet is still well out beyond Mars and is currently 400 million kilometres from the sun, but is already pungent given the chemicals it is emitting.

It is a bit of a chemistry set with hydrogen sulphide (bad eggs), ammonia (urine), vinegar (sulphur dioxide) and others including formaldehyde, hydrogen cyanide and methanol.

But mission control was a bit surprised that it is so smelly long before it starts to heat up. It begs the question what else might emerge when the tail forms and gases and dust begin venting from the surface.

Rosina is one of a collection of instruments on board the Rosetta satellite, and was developed at the University of Bern, Switzerland.

There is huge scientific interest in comets given they are “leftovers” from the material that made the solar system. They tell us what was available when the planets formed and may have been the cause of the Earth having so much water.

Comet Churyumov-Gerasimenko measures 3.5km by 4km and scientists believe most of this is ice. A heavy bombardment of Earth by incoming comets could have helped to top-up our oceans, not to mention delivering large amounts of organic chemicals that could have supported the development of early life.

A highlight of the mission comes on November 12th when Rosetta releases a comet lander called Philae. It will land on the comet, take pictures and test what it is made of through direct contact rather than remote sampling.