Saturn’s Titan home to sea as salty as Earth’s Dead Sea

The moon continues to prove itself as an endlessly fascinating and mysterious world, say experts

 
Published: Saturday 04 July 2015

Researchers found that Titan's ice shell, which overlies a very salty ocean, varies in thickness around the moon, suggesting the crust is in the process of becoming rigid.(Image Credit: NASA/JPL/SSI/Univ. of Arizona/G. Mitri/University of Nantes)

An analysis of 10 years of data has concluded that the ocean inside Saturn’s largest moon, Titan, might be as salty as Earth's Dead Sea. The data was gathered by Cassini, NASA’s unmanned spacecraft or Cassini-Huygens Probe, which was sent to Saturn in June 2004.

The conclusion was drawn after studying gravity and topography information collected by Cassini’s repeated flybys of Titan. Using the data, researchers presented a model structure for Titan, resulting in an improved understanding of the structure of the moon's outer ice shell. The findings were published in the journal Icarus.

Saturn, also known for its rings, has 53 known moons and nine provisional moons, according to NASA. "Titan continues to prove itself as an endlessly fascinating world, and with our long-lived Cassini spacecraft, we’re unlocking new mysteries as fast as we solve old ones," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, in a press release by NASA.

Additional findings support previous indications that the moon's icy shell is rigid and in the process of freezing solid. Researchers found that a relatively high density was required for Titan's ocean in order to explain the gravity data. This indicates the ocean is probably an extremely salty brine of water mixed with dissolved salts likely composed of sulphur, sodium and potassium. The density indicated for this brine would give the ocean a salt content roughly equal to the saltiest bodies of water on Earth.

"This is an extremely salty ocean by Earth standards," said the paper's lead author, Giuseppe Mitri of the University of Nantes in France. "Knowing this may change the way we view this ocean as a possible abode for present-day life, but conditions might have been very different there in the past."

A further consequence of a rigid ice shell, according to the study, is that any outgassing of methane into Titan's atmosphere must happen at scattered "hot spots"—like the hot spot on Earth that gave rise to the Hawaiian Island chain. At such hot spots, magma from within the mantle pushes up the Earth's crust, resulting in the formation of an undersea volcano.   Over time the volcano emerges from beneath the sea, and an island is born. How methane got into the moon's atmosphere of Titan has long been of great interest to researchers, as molecules of this gas are broken apart by sunlight on short geological timescales. Titan's present atmosphere contains about five per cent methane.
 

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