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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.
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."
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. 
Right: 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.
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. |
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