text: That heady bouquet, according to Swiss researchers, is the 'perfume' of comet 67P/Churyumov-Gerasimenko. 
   
   Scientists at the University of Bern said Thursday they have determined what the comet would smell like by analyzing the chemicals in its coma, the fuzzy head surrounding the nucleus. 
   
   For this, they used one of the instruments aboard the European spacecraft Rosetta that is preparing to drop a lander onto the comet's icy surface Nov. 12. 
   
   Project leader Kathrin Altwegg of the University of Bern said the aroma will get stronger as 67P gets closer to the sun, causing it to release more gas and form the coma characteristic of comets. ||||| With inputs from Kathrin Altwegg, ROSINA science team, University of Bern. 
   
   Since early August, the Rosetta Orbiter Sensor for Ion and Neutral Analysis (ROSINA) has been ‘sniffing the fumes’ of 67P/C-G with its two mass spectrometers. 
   
   As reported previously in this blog, even though the comet is still more than 400 million kilometres from the Sun, the mixture of molecules detected in the comet’s coma is surprisingly rich already. Before arriving at 67P/C-G, the ROSINA team thought that at these vast distances from the Sun, its relatively low intensity would only release the most volatile molecules via sublimation, namely carbon dioxide and carbon monoxide. 
   
   However, ROSINA has detected many more molecules. Indeed, as of our 11 September report, ROSINA’s inventory of detected gases 67P/C-G looked like this: 
   
   Water (H 2 O) 
   
   Carbon monoxide (CO) 
   
   Carbon dioxide (CO 2 ) 
   
   Ammonia (NH 3 ) 
   
   Methane (CH 4 ) 
   
   Methanol (CH 3 OH) 
   
   But today we can report that the following have also been detected: 
   
   Formaldehyde (CH 2 O) 
   
   Hydrogen sulphide (H 2 S) 
   
   Hydrogen cyanide (HCN) 
   
   Sulphur dioxide (SO 2 ) 
   
   Carbon disulphide (CS 2 ) 
   
   If you could smell the comet, you would probably wish that you hadn’t 🙂 
   
   As the Kathrin Altwegg, principal investigator for ROSINA, put it: “The perfume of 67P/C-G is quite strong, with the odour of rotten eggs (hydrogen sulphide), horse stable (ammonia), and the pungent, suffocating odour of formaldehyde. This is mixed with the faint, bitter, almond-like aroma of hydrogen cyanide. Add some whiff of alcohol (methanol) to this mixture, paired with the vinegar-like aroma of sulphur dioxide and a hint of the sweet aromatic scent of carbon disulphide, and you arrive at the ‘perfume’ of our comet.” 
   
   While this is unlikely to be a particularly attractive perfume, remember that the density of these molecules is very low, and that the main part of the coma is made up of water and carbon dioxide, mixed with carbon monoxide. 
   
   The key point, however, is that a detailed analysis of this mixture and how it varies as 67P/C-G grows more active will allow scientists to determine the comet’s composition. Further work will show how 67P/C-G compares with other comets, for example by revealing differences between comets originating from the Kuiper Belt (like 67P/C-G) and comets that hail from the distant Oort cloud (like Comet Siding Spring, which recently flew past Mars). The goal is to gain insights into the fundamental chemical make-up of the solar nebula from which our Solar System and, ultimately, life itself emerged. 
   
   *For a simple explanation of mass spectra and associated units, see Wikipedia’s entry: http://en.wikipedia.org/wiki/Mass_spectrum 
   
   For more detailed information on ROSINA, see our description here. ||||| Rotten eggs, horse pee, alcohol and bitter almonds: this is the bouquet of odours you would smell if a comet in deep space could be brought back to Earth, European scientists said Rotten eggs, horse pee, alcohol and bitter almonds: this is the bouquet of odours you would smell if a comet in deep space could be brought back to Earth, European scientists said on Thursday. 
   
   An instrument aboard the probe Rosetta has detected some intriguing chemical signatures from Comet 67P/Churyumov-Gerasimenko since their rendezvous in deep space in August, they said. 
   
   Molecules include ammonia, methane, hydrogen sulphide, hydrogen cyanide and formaldehyde. 
   
   "If you could smell the comet, you probably wish that you hadn't," the team said wryly in a blog posted on the European Space Agency (ESA) website. 
   
   The device, called Rosina-DFMS, is a mass spectrometer—it has been analysing the signature of gas given off by the "coma," the comet's head, as the distance closes with the Sun. 
   
   "The perfume of 67P/C-G is quite strong, with the odour of rotten eggs (hydrogen sulphide), horse stable (ammonia) and the pungent, suffocating odour of formaldehyde," said Kathrin Altwegg, Rosina's chief scientist. 
   
   "This is mixed with the faint, bitter, almond-like aroma of hydrogen cyanide. 
   
   "Add some whiff of alcohol (methanol) to this mixutre, paired with the vinegar-like aroma of sulphur dioxide and a hint of the sweet aromatic scent of carbon disulphide, and you arrive at the 'perfume' of our comet." 
   
   The detection of so many different molecules at this stage has been a surprise, ESA said. 
   
   The Rosina team believed only the most volatile molecules—carbon dioxide and carbon monoxide—would be released as the comet's icy surface started slowly to warm. 
   
   On a 6.5-year orbit, 67P/C-G is the target of an ambitious mission to shed light on the origins of comets, ancient travellers of the Solar System. 
   
   Rosetta caught up with it after a six-billion-kilometre (3.75-billion-mile) trek that required four flybys of Earth and Mars, using the planets' gravity as a slingshot to build up speed. 
   
   It is now in close orbit around the comet at a distance of around 400 million kilometres from the Sun. The scout will send down a robot lander, Philae, on November 12 to carry out on-the-spot scientific tests. 
   
   On August 13 next year, the comet and Rosetta will be 185 million kilometres from the Sun, their closest approach to our star. 
   
   Explore further: Comet-chasing probe closes in on target ||||| [image-36] 
   
   The European Space Agency’s Rosetta mission will deploy its lander, Philae, to the surface of comet 67P/Churyumov–Gerasimenko on Nov. 12. 
   
   Rosetta is an international mission spearheaded by the European Space Agency with support and instruments provided by NASA. 
   
   Philae’s landing site, currently known as Site J, is located on the smaller of the comet’s two "lobes," with a backup site on the larger lobe. The sites were selected just six weeks after Rosetta's Aug. 6 arrival at the comet, following the spacecraft's 10-year journey through the solar system. 
   
   In that time, the Rosetta mission has been conducting an unprecedented scientific analysis of the comet, a remnant from early in the solar system’s 4.6-billion-year history. The latest results from Rosetta will be presented when Philae lands, during dedicated press briefings. 
   
   The main focus to date has been to survey 67P/Churyumov–Gerasimenko in order to prepare for the first-ever attempt to soft-land on a comet. 
   
   The descent to the comet is passive and it is only possible to predict that the landing point will be within a "landing ellipse" (typically a few hundred yards or meters in size). For each of Rosetta's candidate sites, a larger area -- four-tenths of a square mile (one square kilometer) -- was assessed. Site J was chosen unanimously as the primary landing site because the majority of terrain within an area that size has slopes of less than 30 degrees relative to the local vertical and because there are relatively few large boulders. The area also receives sufficient daily illumination to recharge Philae and continue surface science operations beyond the initial 64-hour battery-powered phase. 
   
   Over the last two weeks, the flight dynamics and operations teams at ESA have been making a detailed analysis of flight trajectories and timings for Rosetta to deliver the lander at the earliest possible opportunity. 
   
   Two robust landing scenarios have been identified, one for the primary site and one for the backup. Both anticipate separation and landing on Nov. 12. 
   
   For the primary landing scenario, targeting Site J, Rosetta will release Philae at 3:35 a.m. EST (9:35 a.m. Central European Time) at a distance of 14 miles (22.5 kilometers) from the center of the comet, landing about seven hours later. The one-way signal travel time between Rosetta and Earth on Nov. 12 will be 28 minutes and 20 seconds, meaning that confirmation of the landing will arrive at Earth ground stations at around 11 a.m. EST (5 p.m. CET). 
   
   If a decision is made to use the backup site, Site C, separation will occur at 8:04 a.m. EST (2:04 p.m. CET) at a distance of 7.8 miles (12.5 kilometers) from the center of the comet. Landing will occur about four hours later, with confirmation on Earth at around 12:30 p.m. EST (6:30 p.m. CET). The timings are subject to uncertainties of several minutes. 
   
   Final confirmation of the primary landing site and its landing scenario will be made on October 14 after a formal Lander Operations Readiness Review, which will include the results of additional high-resolution analysis of the landing sites conducted in the meantime. Should the backup site be chosen at this stage, landing can still occur on Nov. 12. 
   
   A competition for the public to name the primary landing site will also be announced during the week of Oct. 14. 
   
   Following the Philae landing, the Rosetta orbiter will continue to study the comet and its environment using 11 science instruments for another year as the spacecraft and comet orbit the sun together. The comet is on an elliptical 6.5-year orbit that takes it from beyond Jupiter at its farthest point, to between the orbits of Mars and Earth at its closest to the sun. Rosetta will accompany the comet for more than a year as they swing around the sun and back to the outer solar system again. 
   
   The analyses made by the Rosetta orbiter will be complemented by the measurements performed on the comet by Philae's 10 instruments. 
   
   Comets are time capsules containing primitive material left over from the epoch when the sun and its planets formed. By studying the gas, dust and structure of the nucleus and organic materials associated with the comet, the Rosetta mission should become key to unlocking the history and evolution of our solar system, as well as answering questions regarding the origin of Earth’s water and perhaps even life. 
   
   Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by the German Aerospace Center, Cologne; Max Planck Institute for Solar System Research, Gottingen; National Center of Space Studies of France (CNES), Paris; and the Italian Space Agency, Rome. NASA's Jet Propulsion Laboratory in Pasadena, California, a division of the California Institute of Technology, manages the U.S. participation in the Rosetta mission for NASA's Science Mission Directorate in Washington. 
   
   For more information on the U.S. instruments aboard Rosetta, visit: 
   
   http://rosetta.jpl.nasa.gov 
   
   More information about Rosetta is available at: 
   
   http://www.esa.int/rosetta
target: – Comets stink, and not just because they have the potential to cause cataclysmic devastation if they ever came hurtling through our atmosphere and made impact with Earth. These "cosmic snowballs of frozen gases, rock, and dust roughly the size of a small town" (as described by NASA) literally stink to high heaven, according to scientists at Switzerland's University of Bern. One comet does, anyway: Researchers analyzed the "perfume" of comet 67P/Churyumov-Gerasimenko and said that its BO is apparently a combo of "rotten eggs, horse urine, formaldehyde, bitter almonds, alcohol, vinegar, and a hint of sweet ether," the AP reports. "If you could smell the comet, you would probably wish that you hadn't," reads a blog post on the European Space Agency site. The scientists were able to surmise what the comet would smell like by examining the gas emitted by the "coma," the comet's head, Phys.org reports. Luckily, instead of a squeamish human, a mass spectrometer aboard the space probe Rosetta was assigned the task of parsing out the perfumed molecules of 67P, including ammonia, methane, hydrogen sulfide, hydrogen cyanide, and "the pungent, suffocating (odor) of formaldehyde," notes the ESA post. The probe caught up to the comet in August after chasing it nearly 4 billion miles; it will be sending its Philae robot lander onto the comet proper on Nov. 12, NASA reports. And it appears the comet's odoriferous odyssey is just beginning: The lead scientist on the project says that as 67P gets closer to the sun, it will start stinking up the cosmos even more. (Whatever happened to NASA's plans to harpoon comets?)