Astronomer Athina Koustenis: Huge changes in Titan’s atmosphere may make Saturn’s satellite habitable

As the largest satellite of Saturn, Titan, is reaching the summer solstice of the north hemisphere, the Cassini spacecraft revealed the dramatic season changes in temperature as well as in the composition of its thick atmosphere. The statement was made at the annual congress of the American Astronomical Association in California by Greek astronomer Athina Koustenis of the Observatory Meudon in Paris, chief of research at the National Center for Scientific Research of France, who studies the ‘exotic’ satellite abundant with hydrocarbons.

At the same time, winter in Titan’s south hemisphere is in progress and a strong rotary gas stream has developed in the upper atmosphere of the satellite just over its south pole. These observations, according to Koustenis, indicate a polar reversal since when the Cassini spacecraft reached Saturn’s system in 2004, something similar was happening in the north hemishpere.

The heat circulates and varies in Titan’s atmosphere though the gas movement between its poles. The two hemishpere appear to react differently in the season changes, so in the last four years of winter the temperature in the stratosphere of the south pole dropped by 40 degrees on Celsius scale while the temperature in the south pole increased only by 6 degrees after 2014.

In statements to Athens-Macedonian New Agency, professor Koustenis said that “the exploration of Saturn’s system and particularly of its satellite Titan is at a fascinating peak! We are monitoring Saturn’s orbit around the Sun at a period of 29.5 earth ages and Titan with its axial angle at 26.7 degrees creates huge seasonal variation in its dense nitrogenous atmosphere similar to those observed in earth. This leads to important changes in the atmosphere as in the chemical composition and the patterns of the rotation of atmospheric currents at the middle and upper layers of the atmosphere, namely the stratosphere and the mesosphere.

Koustenis noted that “Cassini offers us the possibility to monitor very closely the reactions of Titan’s atmosphere to solar radiation that led us to the discovery of the dramatic changes in the temperature and composition that occured after the equinox.” From 2010 and over was observed the rapid start and enrichment of Titan’s south pole with all kinds of gas trails and particularly with complex hydrocarbons and nitriles in the atmosphere. “We search for new complex of cells in Titan’s south pole with aim to observe how complicated and advanced is the atmosphere’s chemistry and how possible is the existence of a liquid ocean under the surface of Titan, a fact that would make Titan a star with habitable potential outside our solar system”.

Koustenis said that “all the scientists involved in the observation of Titan are very excited with the possibility to study further this phaenomenon during the last age of Cassini’s mission that will last until 2017, a mission that will reach 13 years of observation and would have cover half of Titan’s year, something that imposes even tighter restrictions in relation with the understanding of Titan’s season variations.