Ocean on Saturn's moon Titan could be as salty as Earth's Dead Sea

Date:

July 2, 2014

Source:

NASA/Jet Propulsion Laboratory

Summary:

Scientists analyzing data from NASA's Cassini mission have firm evidence the ocean inside Saturn's largest moon, Titan, might be as salty as Earth's Dead Sea. The new results come from a study of gravity and topography data collected during Cassini's repeated flybys of Titan during the past 10 years. Using the Cassini data, researchers presented a model structure for Titan, resulting in an improved understanding of the structure of the moon's outer ice shell.

Scientists analyzing data from NASA's Cassini mission have firm evidence the ocean inside Saturn's largest moon, Titan, might be as salty as Earth's Dead Sea.

The new results come from a study of gravity and topography data collected during Cassini's repeated flybys of Titan during the past 10 years. Using the Cassini 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 are published in this week's edition of the journal Icarus.

"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 in Pasadena, California, who was not involved in the study.

Additional findings support previous indications 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 sulfur, 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."

Cassini data also indicate the thickness of Titan's ice crust varies slightly from place to place. The researchers said this can best be explained if the moon's outer shell is stiff, as would be the case if the ocean were slowly crystalizing and turning to ice. Otherwise, the moon's shape would tend to even itself out over time, like warm candle wax. This freezing process would have important implications for the habitability of Titan's ocean, as it would limit the ability of materials to exchange between the surface and the ocean.

A further consequence of a rigid ice shell, according to the study, is 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. Titan's methane does not appear to result from convection or plate tectonics recycling its ice shell.

How methane gets into the moon's atmosphere 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 percent methane. This means some process, thought to be geological in nature, must be replenishing the gas. The study indicates that whatever process is responsible, the restoration of Titan's methane is localized and intermittent.

"Our work suggests looking for signs of methane outgassing will be difficult with Cassini, and may require a future mission that can find localized methane sources," said Jonathan Lunine, a scientist on the Cassini mission at Cornell University, Ithaca, New York, and one of the paper's co-authors. "As on Mars, this is a challenging task."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the mission for NASA's Science Mission Directorate in Washington.

For more information about Cassini, visit:

• http://www.nasa.gov/cassini
• http://saturn.jpl.nasa.gov

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Story Source:

The above story is based on materials provided by NASA/Jet Propulsion Laboratory.Note: Materials may be edited for content and length.

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Journal Reference:

1. Giuseppe Mitri, Rachele Meriggiola, Alex Hayes, Axel Lefevre, Gabriel Tobie, Antonio Genova, Jonathan I. Lunine, Howard Zebker. Shape, topography, gravity anomalies and tidal deformation of Titan. Icarus, 2014; 236: 169 DOI:10.1016/j.icarus.2014.03.018

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Potentially habitable Earth-like planet discovered; May have similar temperatures to our planet

Date:

June 30, 2014

Source:

University of New South Wales

Summary:

A potentially habitable Earth-like planet that is only 16 light years away has been discovered. The "super-Earth" planet, GJ 832 c, takes 16 days to orbit its red-dwarf star, GJ 832, and has a mass at least five times that of Earth. It receives about the same average stellar energy as Earth does and may have similar temperatures to our planet. These characteristics put it among the top three most Earth-like planets.

AUNSW-led team of researchers has discovered a potentially habitable Earth-like planet that is only 16 light years away.

The "super-Earth" planet, GJ 832 c, takes 16 days to orbit its red-dwarf star, GJ 832, and has a mass at least five times that of Earth.

It receives about the same average stellar energy as Earth does, because red dwarfs shine more dimly than our Sun, and may have similar temperatures to our planet.

These characteristics put it among the top three most Earth-like planets, according to the Earth Similarity Index developed by scientists at the University of Puerto Rica in Arecibo.

The international team, led by Dr Robert Wittenmyer in the UNSW School of Physics, report their finding of the planet online ahead of publication in theAstrophysical Journal.

Team member and Head of UNSW's Exoplanetary Science research group, Professor Chris Tinney, says that if the planet has a similar atmosphere to Earth it may be possible for life to survive, although seasonal shifts would be extreme.

"However, given the large mass of the planet, it seems likely that it would possess a massive atmosphere, which may well render the planet inhospitable. A denser atmosphere would trap heat and could make it more like a super-Venus and too hot for life," says Professor Tinney.

The planet was discovered from its gravitational pull on its parent star, which causes the star to wobble slightly. Members of the Anglo-Australian Planet Search team used the Anglo-Australian Telescope to make observations of the planet.

Their data were combined with observations from the 6.5m Magellan Telescope and the European Southern Observatory 3.6m telescope (both in Chile) to make this new discovery.

This team had previously found, in 2009, that the star has a cold Jupiter-like planet with a near-circular orbit of about nine years, called Gliese GJ b.

"With an outer giant planet and an interior potentially rocky planet, this planetary system can be thought of as a miniature version of our Solar System," says Professor Tinney.

On the Earth Similarity Index, or ESI, the highest ranking exoplanet is Gliese 667C c, which is about 23 light years away. It has an ESI of 0.84 compared to Earth's maximum score of 1.0

Next on the list is Kepler-62 e with an ESI of 0.83, although it is much further away -- about 1,200 light years distant. And the new planet -- the closest at just 16 light years away -- comes in third with an ESI of 0.81.

For comparison, the Milky Way is about 100,000 light years across.

The team includes researchers from Australia, the UK, Finland, the US, Italy and Chile.

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Story Source:

The above story is based on materials provided by University of New South Wales.Note: Materials may be edited for content and length.

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