Ingredients for life found on Saturn moon
The geysers of Saturn’s moon Enceladus are gushing up food for life, NASA scientists say.
The geysers of Saturn’s moon Enceladus are gushing up food for life, scientists say.
Researchers report Thursday in the journal Science that the jets of ice and gas gushing from the moon’s south pole contain molecular hydrogen, a chemical characteristic of hydrothermal activity. On Earth, hydrogen provides fuel for communities of organisms that live around vents on the seafloor. Its presence on Saturn’s icy moon suggests that this alien world, which harbors a saltwater ocean encased in a frozen crust, has the right conditions to give rise to microbial life.
“For a microbiologist thinking about energy for microbes, hydrogen is like the gold coin of energy currency,” said Peter Girguis, a deep sea biologist at Harvard University who was not involved in the research. “If you had to have one thing, one chemical compound, coming out of a vent that would lead you to think there’s energy to support microbial life, hydrogen is at the top of that list.”
“It makes the Enceladus ocean seem a heck of a lot more habitable than we were thinking yesterday,” agreed Ariel Anbar, an astrobiologist at Arizona State University. “And wouldn’t we like to know, is there life living there?”
Everything scientists know about biology on Earth suggests that life is irrepressible. It thrives in clouds, in caves, in lakes of meltwater buried half a mile beneath the ice sheets of Antarctica, in boiling water plumes that gush from the ocean’s deepest, darkest depths. Almost no environment is too extreme, as long as water, organic molecules and a bit of energy are available for organisms to exploit. Enceladus (pronounced “en-SELL-a-dis”) provides all three. It’s looking more and more like the most habitable spot in our solar system beyond Earth, and scientists’ best target yet in the search for alien organisms.
And it might not be alone. Images from the Hubble Space Telescope suggest that plumes much like those on Enceladus are also spewing from Jupiter’s moon Europa, NASA announced Thursday.
Like Enceladus, Europa harbors a subsurface saltwater ocean and could contain organic molecules. NASA hopes that Europa’s geysers are likewise connected to the moon’s watery interior. In the coming decade, the space agency will send a probe called the Europa Clipper to seek signs of life on Jupiter’s moon by flying through those plumes.
“In the NASA strategy for searching for life, the key ingredients have always been water, building blocks like carbon, oxygen, nitrogen ... and a source of energy,” said Mary Voytek, a senior scientist for astrobiology at NASA who was not involved in the research.
Enceladus’ geysers have made it a target in the search for extraterrestrial organisms ever since the NASA space probe Cassini detected them in 2005. The plumes are rich with water and organic molecules, and the force with which they gush from the surface suggests that they are driven by a hydrothermal system two-and-a-half times more powerful than the one that powers Yellowstone’s geysers and bubbling hot springs. They are also physical evidence of the water in the moon’s interior, which is heated by the gravitational pull of Saturn.
Voytek said that her boss, NASA’s planetary science director Jim Green, is determined to find organisms beyond Earth before he retires. “You’ve got a couple of years,” he told her, jokingly, when they heard about the Enceladus discovery.
Green is optimistic about his chances. “We’re just on the precipice of moving this whole activity forward,” he said. “I think in our lifetime we’ll be able to answer the question, ‘Are we alone?’”