When a massive saltwater ocean was found hidden beneath the icy crust of Saturn’s moon Enceladus back in 2015, astronomers were cautiously optimistic that this watery world could have just the right conditions to host life. Now, thanks to a new study, Enceladus’ stock has gone up — way up.
Using data from a dead spacecraft, an international team of astronomers has for the first time discovered complex organic (carbon-containing) molecules — the building blocks of life — spewing from Enceladus. The new finding, described in a paper published online June 27 in the journal Nature, makes the small icy moon the most promising place beyond Earth to find life in the solar system.
“Enceladus’ subsurface ocean is a habitable place. The big question is if it is inhabited," Frank Postberg, a planetary scientist at the University of Heidelberg in Germany and the study’s lead author, told NBC News MACH in an email.
It’s too soon to conclude that life exists on Enceladus, the sixth-largest of Saturn’s 62 confirmed moons. But scientists are intrigued because liquid water, a source of energy and organic molecules are three key ingredients to support life as we know it — and Enceladus has all three.
“We now know that Enceladus’ ocean has all of these ingredients, today,” Christopher Glein, a geochemist at the Southwest Research Institute in San Antonio, Texas, and a co-author of the study, told MACH in an email. “Besides Earth, no other place in the solar system has confirmed evidence of all three requirements in a contemporary environment that can support life.”
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The researchers think these organic compounds originate in Enceladus’ core and then flow into the subsurface ocean via hydrothermal vents, before escaping through cracks in the moon's icy crust.
Previously, scientists had detected methane and other simple organic compounds in Enceladus’ plumes. These molecules contain one or two carbon atoms and a few atoms of hydrogen. But the newly detected molecules are made up of hundreds of atoms of carbon, hydrogen, oxygen and nitrogen — all arranged in rings and long chains.
“Large organic molecules are a necessary precursor for life, so this is encouraging,” Postberg said.
The data that led to the discovery was obtained by NASA’s Cassini spacecraft, which spent 13 years orbiting Saturn and its moons before handlers at NASA ended the mission in September 2017 by deliberately driving the probe into the ringed planet.
To determine if Enceladus does host life, researchers are now keen to send a space probe to explore the icy moon up close and determine the origins of the molecules.
Enceladus is a particularly good target for a space probe because its ocean “is being erupted into space where it can be sampled by simply flying a spacecraft through the plume,” said Joseph Spitale, a senior scientist at the Planetary Science Institute in Tuscon, Arizona, who was not involved with the new study.
Spitale said the new discovery isn’t a “smoking gun” for life on Saturn’s moon, but with instruments designed to scour for biosignatures — or signs of life — researchers could gain a better understanding of these complex molecules.
“We found the stuff,” Glein said, “now we need to understand it.”