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Sulfuric Acid Found on Europa

Sulfur from volcanoes on Io may be responsible for a battery acid chemical on Europa with implications for astrobiology.

BASED ON A NASA/JPL PRESS RELEASE

Sulfuric Acid Map of Europa.  Credit JPLSeptember 30, 1999: Sulfuric acid -- a corrosive chemical found on Earth in car batteries -- exists on the frozen surface of Jupiter's icy moon Europa.

"This demonstrates once again that Europa is a really bizarre place," said Dr. Robert Carlson of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, CA. "Sulfuric acid occurs in nature, but it isn't plentiful. You're not likely to find sulfuric acid on Earth's beaches, but on Europa, it covers large portions of the surface."

Right: Frozen sulfuric acid on Jupiter's moon Europa is depicted in this image produced from data gathered by NASA's Galileo spacecraft. The brightest areas, where the yellow is most intense, represent regions of high frozen sulfuric acid concentration. Sulfuric acid is found in battery acid and in Earth's acid rain. This image is based on data gathered by Galileo's near infrared mapping spectrometer. Europa's leading hemisphere is toward the bottom right, and there are enhanced concentrations of sulfuric acid in the trailing side of Europa (the upper left side of the image). This is the face of Europa that is struck by sulfur ions coming from Jupiter's innermost moon, Io. The long, narrow features that crisscross Europa also show sulfuric acid that may be from sulfurous material extruded in cracks. Image Credit: NASA/JPL.

The new findings from NASA's Galileo spacecraft are reported in the Oct. 1 issue of the journal Science. Carlson, the principal investigator for the near-infrared mapping spectrometer aboard Galileo, is the lead author of the paper.

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Although there is no evidence of life on Europa, pictures and other scientific information gathered by the Galileo spacecraft indicate a liquid ocean may lie beneath Europa's icy crust. Water is one key ingredient essential for life.

At first, Carlson thought the spectrometer's findings of sulfuric acid on Europa would quash any talk that life might exist there. "After all, even though we know there are acid-loving bacteria on Earth, sulfuric acid is a nasty chemical," he said. Those thoughts were quickly negated by a colleague, Dr. Kenneth Nealson, head of JPL's astrobiology unit, who was excited by the findings.

"Although sulfur may seem like a harsh chemical, its presence on Europa doesn't in any way rule out the possibility of life," Nealson said. "In fact, to make energy, which is essential to life, you need fuel and something with which to burn it. Sulfur and sulfuric acid are known oxidants, or energy sources, for living things on Earth. These new findings encourage us to hunt for any possible links between the sulfur oxidants on Europa's surface, and natural fuels produced from Europa's hot interior."

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"These findings have helped solve a puzzle that has been nagging at me for a long time," Carlson said. "Data gathered by the spectrometer during observations of Europa had shown a chemical that we couldn't identify. I kept wondering, 'What the heck is this stuff?' Lab measurements now tell us that it is sulfuric acid, and we can start investigating where it comes from and what other materials might be there." For example, some reddish-brown areas on Europa might be caused by sulfur that co- exists with the sulfuric acid.

One theory proposed by Carlson is that the sulfur atoms originate with the volcanoes on Jupiter's fiery moon Io, with the material being ejected into the magnetic environment around Jupiter and eventually whirled toward Europa. Another idea is that the sulfuric acid comes from Europa's interior, beneath the moon's icy crust, ejected by sulfuric acid geysers or oozing up through cracks in the ice.

Galileo image of volcanoes on Jupiter's moon IoRight: Two sulfurous eruptions are visible on Jupiter's volcanic moon Io in this color composite Galileo image. One theory proposed by Carlson to explain sulfurinc acid on Europa is that sulfur atoms originate with the volcanoes on Io, with the material being ejected into the magnetic environment around Jupiter and eventually whirled toward Europa. In this image a bluish plume rises over Io's limb about 86 miles above the surface of a volcanic caldera known as Pillan Patera. More information.

Another theory comes from Carlson's co-author, Professor Robert Johnson of the University of Virginia in Charlottesville, who noted that sodium and magnesium sulfates may have leached onto Europa's surface from underground oceans and then were altered by the intense radiation field. This would produce the frozen sulfuric acid and other sulfur compounds. The new finding is also consistent with earlier Galileo spectrometer data analyses reported by Thomas McCord of the University of Hawaii and other members of the instrument team, who suggested that sulfate salts of this type were present on Europa.

Carlson, Johnson and co-author Mark Anderson, a chemist in JPL's Analytical Chemistry Laboratory, plan to study Jupiter's largest moon, Ganymede, to see if it also contains sulfuric acid.

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The near-infrared mapping spectrometer works like a prism to break up infrared light not visible to the naked eye. Scientists can study the resulting light patterns to determine what chemicals are present, since different chemicals absorb infrared light differently.

Galileo has been orbiting Jupiter and its moons for nearly four years. More information on the Galileo mission is available on the World Wide Web at: http://www.jpl.nasa.gov/galileo An image depicting sulfuric acid on Europa is available on the World Wide Web at: http://photojournal.jpl.nasa.gov/. JPL manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology, Pasadena, CA.Web Links

Related Stories:

Io or Bust -- September 16, 1999. Galileo braves extreme radiation as it plunges toward a close encounter with Io's volcanoes.
Divining Water on Europa -- September 9, 1999. As circumstantial evidence for an underground ocean mounts, JPL scientists try an ingenious experiment to look for hexagonal ice crystals on the surface of Europa.
Taking the Scenic Route to Io -- June 30, 1999. What's happening to the small craters on Callisto? That's the mystery scientists were contemplating as Galileo zoomed past Jupiter's pockmarked moon this morning in an orbit-changing maneuver designed to bring the spacecraft closer to volcanic Io.
Turn Left at Callisto -- May 5, 1999. Galileo heads for a daring encounter with Io's volcanoes.
Galileo buzzes Europa -- Feb. 2, 1999. Galileo executes a close flyby of Europa for the last time during the current mission.
The Frosty Plains of Europa -- Dec. 3, 1998. As Galileo returns new images of Europa, NASA scientists prepare to study samples from a potentially similar environment here on Earth.
Callisto makes a big splash -- Oct. 22, 1998. Scientists may have discovered a salty ocean and a possible ingredient for life on Jupiter's moon.
Galileo takes a close look at icy Europa -- Oct 2, 1998. The spacecraft flew within 2300 miles of the mysterious satellite last weekend.
Clues to possible life on Europa may lie buried in Antarctic ice -- Mar. 5, 1998. Exotic microbial forms turn up in ice above Antarctica's Lake Vostok.

Related Sites:

Ice, Water and Fire the Galileo Europa Mission
Galileo home page at JPL, with the latest on Europa, Callisto and Io
Jet Propulsion Laboratory home page
Io from the SEDS Nine Planets web site
Callisto from the SEDS Nine Planets web site
Jupiter from the SEDS Nine Planets web site
Io: The Prometheus Plume Aug. 18, 1997 Astronomy Picture of the Day
Close-up of an Io volcano Aug. 4, 1995 Astronomy Picture of the Day
Sizzling Io July 6, 1998 Astronomy Picture of the Day


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