Scientists smelled a comet for the first time, and it appears to smell really, really bad. 

"It stinks," Kathrin Altwegg, a researcher at the University of Bern in Switzerland who runs an instrument called ROSINA that picked up the odor, tells NPR. "It's quite a smelly mixture."

The comet 67P/Churyumov-Gerasimenko (67P/C-G) has the aroma of rotten eggs and horse dung, ESA, whose Rosetta space probe has discovered, Giz Magazine reports.

The stench comes from the mixture of gasses on the comet. 

"The perfume of 67P/C-G is quite strong, with the odor of rotten eggs (hydrogen sulphide), horse stable (ammonia), and the pungent, suffocating odour of formaldehyde," Altwegg tells Giz Magazine.  

Scientists never discovered the odor of a comet before because this is the closest they have ever been to a comet before. While studying a comet in space, scientists are always wearing a space suit.

Although studying the comet on Earth is much smellier than expected, Altwegg doesn't seem to mind.

"It's a little smelly, but at the moment it's a lot of fun to go to work every morning," she tells NPR.