Following the discovery of methane in rock and soil on Mars earlier this month it would seem that the solar system’s previous most likely seat of life, Saturn’s moon Enceladus, wasn’t quite ready to relinquish its title so soon. Spectral analysis from NASA’s Cassini probe has revealed the presence of complex organic molecules ejected from the moon’s icy surface, it was announced in a press release today. And in the fashion of true one-upmanship, the molecules found on Enceladus are over ten times greater in mass than methane.
Scientists at the Southwest Research Institute (SwRI) working with Cassini’s Cosmic Dust Analyzer (CDA) and the SwRI-led Ion and Neutral Mass Spectrometer (INMS) believe that the complex, carbon-rich molecules, heavier than anything that has been observed on Enceladus before, are a result of interactions between the rocky centre and warm water at the surface. Their findings have been published in the June edition of Nature.
“We are, yet again, blown away by Enceladus. Previously we’d only identified the simplest organic molecules containing a few carbon atoms, but even that was very intriguing,” said SwRI’s Dr Christopher Glein, a space scientist specializing in extraterrestrial chemical oceanography. He is the coauthor of a paper in Nature outlining this discovery. “Now we’ve found organic molecules with masses above 200 atomic mass units. That’s over ten times heavier than methane. With complex organic molecules emanating from its liquid water ocean, this moon is the only body besides Earth known to simultaneously satisfy all of the basic requirements for life as we know it.”
Cassini had previously detected organic molecules in a plume of icy material emitted from the body’s sub-surface in 2015. In addition to this samples from the plume were found to be rich in molecular hydrogen, also thought to have formed as a result of interactions between the rocky core and water in hydrothermal environments.
The team are cautious but do draw the link between such complex molecules and simple microbial life.
“Hydrogen provides a source of chemical energy supporting microbes that live in the Earth’s oceans near hydrothermal vents,” said SwRI’s Dr Hunter Waite, INMS principal investigator who also was a co-author of the new paper. “Once you have identified a potential food source for microbes, the next question to ask is ‘what is the nature of the complex organics in the ocean?’ This paper represents the first step in that understanding — complexity in the organic chemistry beyond our expectations!”
“The paper’s findings also have great significance for the next generation of exploration,” Glein said. “A future spacecraft could fly through the plume of Enceladus, and analyze those complex organic molecules using a high-resolution mass spectrometer to help us determine how they were made. We must be cautious, but it is exciting to ponder that this finding indicates that the biological synthesis of organic molecules on Enceladus is possible.”