Comet 67P/Churyumov-Gerasimenko "smells" like rotten eggs

Continuing to track comet 67P/Churyumov-Gerasimenko after catching up in August, ESA's Rosetta spacecraft has just discovered something interesting: this comet smells like rotten eggs and horse manure.

Rosetta used the Orbital Sensing and Ion Neutral Gas Analyzer (ROSINA) to determine the "stink" of 67P/Churyumov-Gerasimenko. This system consists of two large spectrometers: the dual-focus mass spectrometer DFMS and the reflectance time-of-flight spectrometer (RTOF) that allows analysis of cometary composition and the cometary pressure sensor (COPS) that helps determine the pressure of gases in the cometary head.

The spectrometers are designed to measure a wide range of molecules from hydrogen to complex organics. In addition, the pressure sensor can map changes in comet head pressure as well as large differences in concentrations of ions and neutral gases.

The smell of comet 67P/Churyumov-Gerasimenko is actually only theoretically determined because the comet's head is essentially a giant vacuum with molecular trails. However, if these molecules were concentrated, the comet would have a very unpleasant smell. Scientists believe that because 67P/Churyumov-Gerasimenko is flying so far from the Sun, only highly volatile molecules such as CO or CO2 are emitted and detected by the above system. However, Rosetta has detected a mixture of gases in the comet's head and this mixture includes: water, CO, CO2, ammonia (NH3), methane (CH4), methanol (CH3OH), formaldehyde (CH2O), hydrogen sulfide (H2S), hydrogen cyanide (HCN), sulfur dioxide (SO2) and carbon disulfide (CS2).

Among them, hydrogen sulfide (H2S), ammonia (NH3) and formaldehyde (CH2O) are the main components that make up the comet's rotten smell. Kathrin Altwegg - the head researcher of the ROSINA system said: "The smell of 67P/Churyumov-Gerasimenko is quite strong, like the smell of rotten eggs (H2S), the smell of horse manure (NH3) and the suffocating smell of formaldehyde. They are mixed with the slightly sour smell of hydrogen cyanide along with the mild alcohol smell of methanol, the vinegar smell of sulfur dioxide and the slightly sweet smell of carbon disulfide and we have the scent of a comet."

Gas rising from the comet 67P/Churyumov-Gerasimenko.​

Launched in 2004, Rosetta caught up with Comet 67P/Churyumov-Gerasimenko after three flybys of Earth, one flyby of Mars and one flyby of Jupiter to gain enough velocity to be driven by the planets' gravity. During its 10-year journey, Rosetta encountered asteroids such as Steins and Lutetia, then spent 31 months in a sleep mode to conserve resources before resuming its hunt for Comet 67P/Churyumov-Gerasimenko. Since its capture on 6 August, the ESA's unmanned spacecraft has stabilized its orbit and is now preparing for its historic landing on the comet's surface.

ESA says that by measuring the gases, astronomers can not only determine the comet's chemical composition, how its origin in the Kuiper Belt differs from that of comets originating in the Oort cloud, and even find evidence of how life began in the solar system.

Source Tinhte/ESA