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The Rosetta comet orbiter (and soon lander) has spent the last couple months sniffing the scent of the Churyumov-Gerasimenko comet, and has just reported the results: it stinks. You might expect a rock that spends all its time in a vacuum to be fairly inoffensive, but in fact exposure to sunlight is causing it to give off quite an aroma: hydrogen sulfide, ammonia, formaldehyde, hydrogen cyanide, and other caustic gases would make it smell "suffocating," like a cross between a filthy barn, an embalming room, and a rotten egg.

That may not sound pleasant, but it's a fascinating mix to any scientist interested in the early chemical conditions of our solar system — conditions that would have governed the formation of Earth and subsequent emergence of life. Churyumov-Gerasimenko hails from the Kuiper belt, and its aroma will be compared to comets from the neighboring Oort cloud. Differences between the two could help further explain the makeup of the solar nebula that would eventually become our system. Kathrin Altwegg of the University of Bern explained: "Its perfume may not be Chanel No.5, but comets clearly have their own preferences."



—Devin Coldewey