Saturn's Moon Enceladus Exhibits Signs of Hydrothermal Activity

Posted on March 14, 2015

Saturn's moon Enceladus is exhibiting signs of hydrothermal activity according to scientists studying data provided by NASA's Cassini spacecraft. The hydrothermal activity may resemble that seen in the deep oceans on Earth. It is the first evidence of active hot-water chemistry beyond planet Earth.

John Grunsfeld, astronaut and associate administrator of NASA's Science Mission Directorate, says in a statement, "These findings add to the possibility that Enceladus, which contains a subsurface ocean and displays remarkable geologic activity, could contain environments suitable for living organisms. The locations in our solar system where extreme environments occur in which life might exist may bring us closer to answering the question: are we alone in the universe"

Hydrothermal activity is a natural occurring process in Earth's oceans. NASA scientists say it happens when "seawater infiltrates and reacts with a rocky crust and emerges as a heated, mineral-laden solution." Scientists conducting experiments and running simulations using the Cassini data have come to the conclusion that a similar process may occur on Enceladus.

Cassini's cosmic dust analyzer (CDA) instrument repeatedly detected miniscule rock particles rich in silicon on Enceladus. The CDA research team concluded these particles must be grains of silica. The grains had a consistent size and the largest size of the grains was 6 to 9 nanometers. Hydrothermal activity is the most common way to form silica grains like this on Earth. The scientists say in a Nature paper that experiments show that "silica particles with the observed size distribution can be produced only under rather specific thermo-physical conditions."

A separate group of researchers have also determined that hydrothermal activity is one of two likely sources of methane in the plume of gas and ice particles that erupts from the south polar region of Enceladus. The diagram below shows how methane gets trapped in the ocean on Enceladus. A larger version of this diagram can be found here.

Research papers on the hydrothermal activity on Enceladus were published in Nature and in Geophysical Research Letters.

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