In the atmosphere of Titan, the largest moon of Saturn, ice clouds have been found consisting of a mixture of hydrogen cyanide and benzene. Scientists from NASA were able to determine the chemical composition by analyzing the data obtained by the infrared spectrometer on board the Cassini probe back in 2015. This is reported by a NASA press release.
Scientists from NASA continue to analyze data obtained from the Cassini probe, which for 13 years explored Saturn, its moons and rings, and on September 15, 2017 completed its mission. One of the goals of the Cassini mission and the Huygens lander was to study the chemical composition of the surface and atmosphere of Saturn's largest moon Titan. Clouds over Titan were first recorded back in the 1990s with the Hubble telescope, and Cassini was able to show that rain clouds are composed of methane, are located at a distance of several tens of kilometers from the surface of Saturn's moon and can form characteristic structures in the form stripes in the polar regions.
Scientists have now analyzed three characteristic spectra obtained from July to November 2015 while examining higher ice clouds near the satellite's South Pole. When the signal was received, these clouds were at an altitude of 160 to 210 kilometers from the satellite's surface. The data on their chemical composition were obtained using the CIRS infrared spectrometer, which was on board the probe.
The resulting spectrum did not match any of the rich spectrum of substances found on the surface of Titan, in pure form. Therefore, the main task of the researchers in the laboratory was to select a mixture that would give a spectral signal similar to the received probes. As a result of this search, it turned out that the ice clouds are composed of hydrogen cyanide and benzene.
According to scientists, these two substances condensed together in the region of the South Pole of Titan, but the exact reasons for such joint condensation of these two substances from the general mixture are still unclear. Under ideal conditions, a layered structure should have formed, but the highly nonequilibrium conditions on the satellite contributed to their joint condensation.
Interestingly, ice clouds, composed of a mixture of substances, were already detected by Cassini using infrared spectroscopy in 2005. Then the composition of the clouds over the North Pole of the satellite was analyzed, and a mixture of hydrogen cyano and cyanoacetylene, one of the most complex substances found on Titan, was found in them. Scientists explain the difference in the composition of clouds by the difference in seasonal changes in temperature and composition on the surface of the satellite.
The composition of the mixture of organic substances found on Titan is very diverse. For example, on Titan, acrylonitrile was discovered, an organic substance capable of creating analogs of lipid membranes in liquid methane.
Alexander Dubov
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