Nav: Home

Geochemical process on Saturn's moon linked to life's origin

May 06, 2015

Washington, DC-- New work from a team including Carnegie's Christopher Glein has revealed the pH of water spewing from a geyser-like plume on Saturn's moon Enceladus. Their findings are an important step toward determining whether life could exist, or could have previously existed, on the sixth planet's sixth-largest moon.

Enceladus is geologically active and thought to have a liquid water ocean beneath its icy surface. The hidden ocean is the presumed source of the plume of water vapor and ice that the Cassini spacecraft has observed venting from the moon's south polar region. Whenever there's the possibility of liquid water on another planetary body, scientists begin to ask whether or not it could support life.

The present team, including lead author Glein, John Baross of the University of Washington, and J. Hunter Waite Jr. of the Southwest Research Institute, developed a new chemical model based on mass spectrometry data of ice grains and gases in Enceladus' plume gathered by Cassini, in order to determine the pH of Enceladus' ocean. The pH tells us how acidic or basic the water is. It is a fundamental parameter to understanding geochemical processes occurring inside the moon that are considered important in determining Enceladus' potential for acquiring and hosting life. Their work is published in the journal Geochimica et Cosmochimica Acta.

The team's model, constrained by observational data from two Cassini teams, including one led by coauthor Waite, shows that the plume, and by inference the ocean, is salty with an alkaline pH of about 11 or 12, which is similar to that of glass-cleaning solutions of ammonia. It contains the same sodium chloride (NaCl) salt as our oceans here on Earth. Its additional substantial sodium carbonate (Na2CO3) makes the ocean more similar to our planet's soda lakes such as Mono Lake in California or Lake Magadi in Kenya. The scientists refer to it as a "soda ocean."

"Knowledge of the pH improves our understanding of geochemical processes in Enceladus' 'soda ocean,'" Glein explained.

The model suggests that the ocean's high pH is caused by a metamorphic, underwater geochemical process called serpentinization. On Earth, serpentinization occurs when certain kinds of so-called "ultrabasic" or "ultramafic" rocks (low in silica and high in magnesium and iron) are brought up to the ocean floor from the upper mantle and chemically interact with the surrounding water molecules. Through this process, the ultrabasic rocks are converted into new minerals, including the mineral serpentine, after which the process is named, and the fluid becomes alkaline. On Enceladus, serpentinization would occur when ocean water circulates through a rocky core at the bottom of its ocean.

"Why is serpentinization of such great interest? Because the reaction between the metallic rocks and the ocean water also produces molecular hydrogen (H2), which provides a source of chemical energy that is essential for supporting a deep biosphere in the absence of sunlight inside moons and planets," Glein said. "This process is central to the emerging science of astrobiology, because molecular hydrogen can both drive the formation of organic compounds like amino acids that may lead to the origin of life, and serve as food for microbial life such as methane-producing organisms. As such, serpentinization provides a link between geological processes and biological processes. The discovery of serpentinization makes Enceladus an even more promising candidate for a separate genesis of life."

Even beyond the search for life-hosting conditions on other planetary bodies, the team's work demonstrates that it is possible to determine the pH of an extraterrestrial ocean based on chemical data from a spacecraft flying through a plume. This may be a useful approach to searching for habitable conditions in other icy worlds, such as Jupiter's moon Europa.

"Our results show that this kind of synergy between observations and modeling can tell us a great deal about the geochemical processes occurring on a faraway celestial object, thus opening the door to an exciting new era of chemical oceanography in the solar system and beyond." Glein added.
-end-
This work was supported by the Deep Carbon Observatory, the Carnegie Institution for Science, the NASA Astrobiology Institute, and the Cassini Project.

The Carnegie Institution for Science is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.

Carnegie Institution for Science

Related Cassini Articles:

NASA's Cassini, Voyager missions suggest new picture of sun's interaction with galaxy
New data from three NASA missions show that the heliosphere -- the bubble of the sun's magnetic influence that surrounds the inner solar system -- may be much more compact and rounded than previously thought.
Cassini detects hydrothermal processes on one of Saturn's moons
In 2015, during the Cassini spacecraft's deepest-ever dive into the plume of spray that emanates from cracks in the south polar region of the ice-covered Saturnian moon Enceladus, instruments detected the presence of molecular hydrogen in the plume vapor.
Saturn's rings viewed in the mid-infrared show bright Cassini Division
Researchers has succeeded in measuring the brightnesses and temperatures of Saturn's rings using the mid-infrared images taken by the Subaru Telescope in 2008.
UM researcher, NASA team discover how water escapes from Saturn
A University of Montana professor who studies astrophysics has discovered how water ions escape from Saturn's environment.
NASA's Cassini finds monstrous ice cloud in Titan's south polar region
New observations made near the south pole of Titan by NASA's Cassini spacecraft add to the evidence that winter comes in like a lion on this moon of Saturn.
Wobbling of a Saturn moon hints at what lies beneath
Using instruments aboard the Cassini spacecraft to measure the wobbles of Mimas, the closest of Saturn's regular moons, a Cornell University astronomer publishing in Science, Oct.
Cassini reports sub-surface ocean on Enceladus
New results from the Cassini spacecraft, which has been among Saturn's moons for the past 10 years, show that Enceladus -- one of the planet's smaller moons -- harbors an ocean of water beneath 18 to 24 miles (30 to 40 kilometers) of ice.
NASA's Cassini spacecraft finds ingredient of household plastic in space
NASA's Cassini spacecraft has detected propylene, a chemical used to make food-storage containers, car bumpers and other consumer products, on Saturn's moon Titan.
New Cassini data from Titan indicate a rigid, weathered ice shell
An analysis of gravity and topography data from Saturn's largest moon, Titan, has revealed unexpected features of the moon's outer ice shell.
NASA's Cassini sees abrupt turn in Titan's atmosphere
Data from NASA's Cassini spacecraft tie a shift in seasonal sunlight to a wholesale reversal, at unexpected altitudes, in the circulation of the atmosphere of Saturn's moon Titan.

Related Cassini Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...