While the Rosetta space probe’s Philae lander prepares to land on the comet 67P/Churyumov-Gerasimenko on November 12, the analyzes at a distance go on. The comet is about 450 million kilometers (about 280 million miles) from the Sun and its activity is increasing due to the sublimation of the ice, which becomes steam. The ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instrument has already analyzed some emissions finding that the comet really stinks.

The two ROSINA’s mass spectrometers can determine the composition of the atmosphere and the ionosphere of the comet formed due to its activities, measure the temperature and speed of the gas and the ions and investigate the reactions in which they’re involved. ROSINA’s pressure sensor allows to determine the density of the gas and to evaluate its flow.

Because of the distance of the comet from the Sun, ESA’s scientists expected that only the most volatile molecules would be released together with water, meaning carbon dioxide and carbon monoxide. Based on the history of observations of other comets, scientists expect an increased activity with the release of other molecules at a greater proximity, around 300 million kilometers (about 186 million miles), in early spring 2015.

Instead, once again 67P/Churyumov-Gerasimenko reserved a surprise and during the course of September ROSINA detected several other compounds. They’re not only simple molecules such as water but also other a bit more complex and not exactly good perfumes. There’s formaldehyde but also hydrogen sulfide, the substance that creates the smell of rotten eggs. The unpleasant odors continue with ammonia and sulfur dioxide. By comparison, hydrocyanic acid and methanol are pleasant.

From the scientific point of view, this mixture of substances is really interesting. One of the most important goals of the Rosetta mission is to study the origin of the materials that make up the solar system to better understand the formation of planets. In particular, there’s an interest in the formation of the Earth and the origin of life on the planet.

Comets are fossils from the early age of the solar system. Part of them have changed very little for some billion years, allowing us to somehow look back in time. An analysis of the differences with comets from the Oort cloud such as C/2013 A1 Siding Spring will be useful in this research[ad name=”eBayUSUKAstronomy”].