Surprisingly complex chemistry on a comet

Comets date back to the time when the Sun, planets, and other stars in our solar system were formed. Due to this, they are relics of the same raw material that gave rise to all those celestial bodies, and therefore to investigate comets is to investigate the origin of the Earth and the rest of the solar system.

Now a team including Nora Hänni and Kathrin Altwegg, both from the University of Bern in Switzerland, have for the first time succeeded in identifying a whole series of complex organic substances in a comet.

The ROSINA high-resolution mass spectrometer, on board the European Space Agency’s (ESA) Rosetta space probe, collected data on comet 67P/Churyumov-Gerasimenko, also known as Chury, between 2014 and 2016. These data allow now to Hänni, Altwegg and their colleagues to provide new and illuminating data on the rich organic content of Chury.

When Chury reached its perihelion, the closest point to the Sun, it became very active. Sublimation of cometary ices created an outflow that carried dust particles with it. The ejected particles were heated by solar irradiation to higher temperatures than usual on the comet’s surface. All of this makes larger and heavier molecules more easily analyzable.

Among the substances identified, there are organic compounds that have never before been found in a comet. His presence in Chury has been a surprise. For example, there is naphthalene, like the one that gives its characteristic smell to the mothballs that we put in clothes that are going to be stored for a long time. Benzoic acid, a typical component of frankincense, has also been discovered. Another striking substance found on the comet is benzaldehyde, widely used in the food industry to add almond flavor to some products.

As Comet Chury approached its point of closest approach to the Sun, large masses of gas and dust emanated from the cometary surface, as can be seen in the halo (illuminated by sunlight) that surrounds it, especially in the Upper area. (Photo: © ESA / Rosetta / NAVCAM. CC BY)

Another class of substances found in Chury are of the prebiotic type. Specifically, they serve as key intermediates in the synthesis of various biomolecules (eg amino acids). This reinforces the belief that comets that fell on Earth during its infancy may have been partially responsible for the emergence of life here, by supplying organic materials essential for life to form.

Hänni, Altwegg and their colleagues present the details of their analysis in the academic journal Nature Communications, under the title “Identification and characterization of a new ensemble of cometary organic molecules”. (Font: NCYT by Amazings)