Liquid water mixing with rock on this distant moon could create chemistry necessary for life, scientists report.
For years, the motto among astrobiologists — people who look for life in distant worlds, and try to understand what life is, exactly — has been “follow the water.” You have to start the search somewhere, and scientists have started with liquid water because it’s the essential agent for all biochemistry on Earth.
Now they’ve followed the water to a small, icy moon orbiting Saturn. Scientists reported Thursday that Enceladus, a shiny world about 300 miles in diameter, has a subsurface “regional sea” with a rocky bottom.
The moon’s liquid reservoir had already been inferred from the presence of plumes of water vapor emerging from the south pole. The plumes stunned scientists when they were detected by NASA’s Cassini spacecraft in 2005. This latest report adds the detail of the rocky sea floor, which is significant because the contact between liquid water and rock creates the potential for the kind of interesting chemistry that gets astrobiologists excited.
This bulletin from the outer solar system could boost Enceladus as a possible target of a future robotic space mission. A spacecraft could fly through the plumes and study whatever’s coming out of the moon — something Cassini has done, but with instruments from the previous century that were not designed to look for signs of life.
To become a target for a new mission, however, Enceladus would probably need to outshine Jupiter’s moon Europa, which also appears to have subsurface ocean and also has plumes shooting water vapor into space.
NASA is putting together preliminary designs for a possible Europa mission, though budgetary pressures for now make any new major, costly venture in the outer solar system problematic.
“I love Mars, but I think the two of them” — Enceladus and Europa — “provide the highest probability of finding extant life,” said Mary Voytek, senior scientist for NASA’s astrobiology program. She said she is “torn” about which moon would be the better destination for a robotic probe.