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Physical Chemistry

Cassini Spacecraft To Dive Through Water Jets On Saturn’s Moon

Space Chemistry: Plumes from Enceladus may reveal whether the moon can host life

by Elizabeth K. Wilson
October 27, 2015

CORRECTION: This story was updated on Oct. 28, 2015, to correct the day of the week that Cassini is set to fly by Enceladus.

On Wednesday, Oct. 28, the National Aeronautics & Space Administration’s Saturn-orbiting spacecraft Cassini is set to fly through plumes of water on Saturn’s moon Enceladus. This historic maneuver may help establish the moon’s ability to support life.

JET CLOSEUP
[+]Enlarge
Credit: NASA/JPL/Space Science Institute
Cassini will fly through jets of water that spew from fractures in the ice, known as “tiger stripes,” covering the lower portion of Enceladus.
20151027lnp1-enceladus.jpg
Credit: NASA/JPL/Space Science Institute
Cassini will fly through jets of water that spew from fractures in the ice, known as “tiger stripes,” covering the lower portion of Enceladus.
JET CLOSEUP
Credit: NASA
This animation shows how Cassini will fly through ice water plumes on Enceladus.

Scientists recently discovered that a salty ocean lies beneath the ice-covered Enceladus. Similarly, one of Jupiter’s moons, Europa, is also believed to have a sub-ice ocean, making these bodies of intense interest for future missions looking for habitable spots in the solar system.

“This is a very big step in a new era of exploring ocean worlds in our solar system,” Curt Niebur, Cassini program scientist at NASA, said at an Oct. 26 conference announcing the Enceladus flyby.

Cassini has flown by Enceladus water plumes, which spray through fractures in its icy surface, many times before. However, this event will take the craft only 30 km above the surface, and directly through the plumes, where spectrometers will monitor the chemical makeup of the liquid.

During the previous flybys, scientists had identified NaCl, CO2, and organic molecules such as methane, propane, acetylene, and formaldehyde, in the plumes. They also know the water’s pH falls between 9 and 11, conditions that are “favorable for life,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory, during the press conference.

With this close flyby, the scientists will look for confirmation of the presence of H2, which is produced through geothermal chemistry, and will help establish Enceladus’s level of hydrothermal activity.

The team hopes to identify more organic molecules in this flyby, but they emphasized that the craft’s spectrometers can’t detect large biomolecules, such as DNA.

After the flyby, the team will spend weeks analyzing the data before announcing their findings.

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Comments
Stuart j. Mickel (October 28, 2015 7:51 PM)
Surely for live the optimal pH is around 7.4. Values of 9 -11 are very basic.
Elizabeth Wilson (November 2, 2015 10:32 PM)
Actually, some extremeophiles on Earth can live at these high pHs. Thanks for your comment!

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