The findings were published in Friday's issue of Science magazine. Mark Anderson, a chemist at NASA's Jet Propulsion Laboratory who works with Carlson, tested particular results from the prism-like instrument against various suspected chemical compounds in a laboratory until he got the match with a frozen solution of sulfuric acid. The result came from data collected by Galileo's Near-Infrared Mapping Spectrometer, which effectively breaks up infrared light not visible to the naked eye. Scientists look at the pattern of diffracted light to learn what chemicals are present since they absorb light differently. Although sulfuric acid is very corrosive, scientists recently have learned it and other sulfur compounds also can be a source of food for bacteria living in hostile environments on Earth.
Water is a key ingredient for life.
Ken Nealson, head of JPL's astrobiology unit, said the acid's presence excited him about the possibility of life on Europa. Bacteria are very good at exploiting chemical energy sources, even inorganic sources like sulfuric acid, Anderson said. Peroxide finding pointed to sulfur Carlson, Anderson and their colleagues reported earlier this year finding evidence of peroxide at Europa's surface. The peroxide data pointed also to sulfur, and scientists believed that element could easily come to Europa from its neighboring jovian moon Io, which is highly volcanic and spews sulfur constantly. Scientists analyzing the Europa spectral data initially looked for sulfates, or sulfur salts.