As Smart News has written before, smell is chemistry. And the specific chemical concoction found on the comet 67P/C-G—made mostly of dust and ice, but also small amounts of organic compounds—means that it has a particularly distinct odor: “rotten eggs, cat urine and bitter almonds,” says New Scientist.
The European Space Agency's Rosetta spacecraft is currently visiting Comet 67P/Churyumov-Gerasimenko, and in a few weeks, a lander launched from Rosetta will touch down on the comet's surface. Yet since August, says the ESA, the orbiter has been chemically analyzing the gas leaking off the comet. What it found was a hearty mix of pungent compounds: ammonia, formaldehyde and hydrogen sulphide, among others.
The chemicals are at at extremely low concentrations, says New Scientist, and would be difficult to sniff out. Yet as the ESA says in their blog post: “If you could smell the comet, you would probably wish that you hadn’t .”
Comets are often considered the left-overs from the formation of the solar system. Comets (or asteroids) are thought to have delivered much of Earth's water. Research over the past few years has also shown that comets carry organic compounds, including amino acids—the most basic building block of DNA.
That comets bear organic molecules, says the American Chemical Society, supports the idea that some of the compounds needed for life on Earth may have originated in outer space. The seed of life, then, may be little more than a cat pee-scented rock in a sea of seared steak and gunpowder.