Water worlds: Distant moons may harbor life under frozen seas, NASA says
The moon has always held a special place in the collective imagination of Earth.
At various times, humans have looked up at our planet's barren counterpart and projected incredible narratives and personalities on it, including the notion that lunar, parallel societies might be peering back at us from its cratered surface.
Some telescopic improvements and a couple moon landings later, none of that has been proved true. However, information released by NASA this week may reveal that part of our problem was a case of the wrong moon.
The space agency announced Thursday its Cassini-Huygens spacecraft, an unmanned probe launched to more than 20 years ago to explore the planet Saturn, had detected molecules indicating conditions potentially favorable to life on one of the planet's many moons. The moon in question, Enceladus, is thought to contain a liquid ocean of water beneath an icy crust, a condition evidenced by intermittent plumes of water vapor launched into space in a geyser-like effect.
UND space studies researcher Mike Gaffey, who is unconnected to the NASA project but has tracked its progress, said the Cassini probe found a form of molecular hydrogen useful as food to some microorganisms while flying past one of those plumes.
"You'd expect to find hydrogen anyway," said Gaffey, given that water molecules being vaporized in space by the sun's UV radiation would bust the molecules apart into atomic units of hydrogen and oxygen. However, he said, the presence of whole molecules of hydrogen tell us the substance is inside the moon itself, thought by NASA scientists to be possibly released through chemical interactions at hydrothermal vents in the bottom of the moon's ocean.
"These are compounds that certain organisms can use to metabolize," Gaffey said. On Earth, some kinds of bacteria can digest these chemical forms of energy and form thriving colonies. Also on our planet, deep-sea hydrothermal vents are often home to veritable oases of life in an otherwise dark and unforgiving environment.
Not long ago, scientists believed ocean bodies such as Earth were a rarity in space. Worlds like Enceladus and Europa—a large moon of Jupiter also believed to harbor a deep ocean beneath a thick, icy crust—are challenging that paradigm. Gaffey said the two moons have joined Mars as the "leading candidates" in the search for extraterrestrial life in our solar system. The case to explore the three frontrunners has been in the making for a long while, so for researchers like Gaffey, Cassini's discovery has been cause for excitement.
"It's like at this point in the movie, I make sure I have fresh popcorn," he said. "The message I've taken away from this is don't be too sure about your absolute knowledge of things. The things you thought impossible might be very possible indeed."