科学美国人60秒:Comet Reeks of Cat Crap and Rotten Eggs

What smells like rotten eggs, a used litter box, and an almond-munching mortician? The answer is one of those dirty snowballs in space, a comet. Comet Churyumov-Gerasimenko, to be exact, which is starting to thaw as it closes in on the Sun.
 
Since August, the European Space Agency’s Rosetta spacecraft has been monitoring the comet. Right now, Churyumov-Gerasimenko is between the orbits of Mars and Jupiter, some 300 million miles from Earth. It’s so chilly out there that scientists expected Rosetta’s instruments to detect scarcely more than odorless carbon dioxide from the comet.
 
But instead Rosetta has also detected hydrogen sulphide—with its rotten egg odor—as well as ammonia, with a smell familiar to anyone who has changed a cat pan. Also in the mix: formaldehyde and methanol, found in embalming fluid, mixed with faint traces of poisonous hydrogen cyanide, which has an almond-like aroma.
 
Rosetta will deploy a probe to land on the comet this November, and will soon gather more pungent whiffs of the comet’s appalling perfume. But by studying this Eau de Comet, researchers hope to better understand the deep—and apparently smelly—chemical origins of our solar system.
 
—Lee Billings
 
(The above text is a transcript of this podcast)