Hunt for life targets Saturn moon
Scientists have found a potential food source for life on a world in our solar system, raising the tantalizing possibility that organisms could thrive in a place besides Earth.
The researchers emphasize they did not find evidence of life itself. What they did find was hydrogen gas in the geyser-like plumes spurting from Saturn’s moon Enceladus. On Earth, hydrogen from seafloor hot springs, also known as hydrothermal vents, serves as food for microbes and as the base of an elaborate ecosystem.
With the new discovery, nearly every item on the list of supplies essential to life has now been found on Enceladus, including carbon-containing molecules called organic compounds, said Hunter Waite of the Southwestern Research Institute in San Antonio, co-author of a new study in this week’s Science.
“Water’s there — check. Organics are in the plume — check. Now we have a chemical source of energy for food — check,” Waite said. Two chemicals essential to living organisms — sulfur and phosphorus — have not been confirmed, but all the same, “Enceladus is rising to the top of habitable places that exist in the solar system.”
Though the tiny moon, only about 300 miles in diameter, looks like a ball of ice, research in the past few years established that it has a salty ocean sloshing underneath its frozen outer shell. Evidence also suggested the water percolates into cracks and fissures in the rocky seafloor.
On Earth, seawater that follows a similar path is an important player in marine life. Heated and filled with minerals, the water wafts from the seabed into the open ocean and nourishes bustling ecosystems. Some researchers even argue that life on Earth arose at hydrothermal vents.
Until now, Enceladus lacked evidence of something to keep life well-fed. In October 2015, NASA sent its Cassini spacecraft diving through the geysers jetting from Enceladus.
After ruling out other possible sources of the hydrogen, the researchers did a “calorie count” of Enceladus’ ocean to determine whether the water holds enough hydrogen and other chemicals to keep living things alive, said study co-author Christopher Glein.
The team concluded that as long as the seawater has a certain level of acidity, it is replete with hydrogen and carbon dioxide, providing “a lot of food for microbes,” Waite said.
The results are “extraordinary and exciting,” said Kevin Hand of NASA’s Jet Propulsion Laboratory, who was not involved in the study. But he pointed out that no one knows the age of Enceladus’ ocean, and a young ocean may mean less time for life to evolve.