An article published in “The Astrophysical Journal Letters” describes an analysis conducted on data collected by ESA’s Rosetta space probe’s ROSINA instrument that allowed to established that the ice on the comet 67P/Churyumov-Gerasimenko has a crystalline form. It may seem a trivial problem, however such nature implies that it originated in the protosolar nebula and is as old as the solar system.
An international team led by a researcher of the LAM (Laboratoire d’Astrophysique de Marseille, the Marseille Astrophysics Laboratory), in France, conducted this study thanks to the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instrument. It’s a mass spectrometer that was used to measure the amount of molecular nitrogen (N2), carbon monoxide (CO), and argon (Ar) present in the ice of the comet 67P/Churyumov-Gerasimenko.
The collected data were compared with those obtained from laboratory experiments on amorphous ice but also with models that describe the composition of the gas hydrates. They are composed of a type of ice crystal in which water molecules can trap the gas. gas hydrates were formed in protosolar nebula by the crystallization of water ice grains that have absorbed gas molecules during the cooling of the nebula.
The ratio between molecular nitrogen and carbon monoxide and that between argon and carbon monoxide on the comet 67P/Churyumov-Gerasimenko correspond to those in gas hydrates. The amount of argon found is one hundred times lower than that which can be trapped in amorphous ice. These analyzes indicate that the ice of the comet is of the crystalline type that formed in the protosolar nebula, therefore along with the solar system.
This research shows that the ratio between the various compounds vary according to their formation temperatures in the protosolar nebula. Those found in the gas hydrates of the comet 67P/Churyumov-Gerasimenko must have formed at temperatures between -228° C and -223° C (between -378.4° and -369.4° Fahrenheit).
One consequence of these conclusions is that there had to be more gas hydrates than amorphous ice also in the materials gas giants and their ice moons formed. A first check might arrive from the summer of 2016, when the NASA’s Juno space probe will reach Jupiter and start sending data about its composition.
