Comet 67P/Churyumov-Gerasimenko discovered to "smell" like rotten eggs.

Continuing its tracking of comet 67P/Churyumov-Gerasimenko after catching up with it in August, ESA's Rosetta spacecraft has just discovered something interesting: the comet smells like rotten eggs and horse manure.

Rosetta used the Orbital Sensor and Neutral Gas Analysis System (ROSINA) to determine the "smell" of 67P/Churyumov-Gerasimenko. This system includes two large spectrometers: a dual-focus mass spectrometer (DFMS) and a time-of-flight reflectometer (RTOF) for analyzing the comet's head composition, and a comet pressure sensor (COPS) for determining the pressure of gases within the comet's head.

Spectrometers are designed to measure a wide range of molecules, from hydrogen to complex organic compounds. In addition, pressure sensors can map changes in the pressure of comet heads, as well as large differences in the density of ions and neutral gases.

In fact, the smell of comet 67P/Churyumov-Gerasimenko was only determined theoretically because the comet's head is essentially a giant vacuum vent with trails of molecules. However, if these molecules were concentrated, the comet would have a very unpleasant odor. Scientists believe that because 67P/Churyumov-Gerasimenko is flying very far from the Sun, only highly volatile molecules like CO or CO2 are released and detected by the system. Nevertheless, Rosetta 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).

Hydrogen sulfide (H2S), ammonia (NH3), and formaldehyde (CH2O) are the main components that give comets their foul smell. Kathrin Altwegg, the lead researcher of the ROSINA system, stated: "The smell of 67P/Churyumov-Gerasimenko is quite strong, like the smell of rotten eggs (H2S), the pungent smell of horse manure (NH3), and the suffocating smell of formaldehyde. These are mixed with the slightly sour smell of hydrogen cyanide, along with a slight alcoholic smell of methanol, the vinegary smell of sulfur dioxide, and the slightly sweet smell of carbon disulfide, and we have the comet's scent."

Gas rises from the head of comet 67P/Churyumov-Gerasimenko.

Launched into orbit in 2004, the Rosetta spacecraft caught up with comet 67P/Churyumov-Gerasimenko after three flybys of Earth, one flyby of Mars, and one flyby of Jupiter to gain the necessary velocity thanks to the gravitational pull of these planets. During its 10-year journey, Rosetta encountered asteroids such as Steins and Lutetia, then spent 31 months in a resting state to conserve resources before resuming its hunt for comet 67P/Churyumov-Gerasimenko. Since catching up on August 6th, the ESA unmanned spacecraft has stabilized its orbit and is now preparing for a historic landing on the comet's surface.

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

Source: Tinhte/ESA