Jets of icy water and gas erupt from Enceladus' south pole. The Cassini space probe captured this photograph and also performed a close flyby of the jets to study their contents. A new analysis of Cassini's data reveals organic compounds never before identified in the Saturn system.NASA/JPL-Caltech/Space Science Institute
The Cassini space probe ended its mission in 2017 with a dramatic plunge into Saturn, yet it continues to fuel discoveries.
In a new analysis of data from one of the probe's instruments, an international team of researchers has identified new organic compounds within jets of icy water erupting from Saturn's moon, Enceladus. The material likely originated in Enceladus' ocean, and adds to mounting evidence that the moon could be habitable.
"We found a rich organic inventory in Enceladus' plume," said Fabian Klenner, a University of Washington postdoctoral researcher of Earth and space sciences and a member of the research team. "Having clear evidence of a variety of organic compounds from inside an extraterrestrial water world is incredible and further strengthens Enceladus' potential for habitability. It appears that Enceladus has all the ingredients for life as we know it."
The results were published Oct. 1 in Nature Astronomy.
Launched in 1997, Cassini performed a yearslong series of flybys of Enceladus while in orbit around Saturn, resolving two longstanding mysteries surrounding the system: the origin of Saturn's enormous but faint E ring and the cause of Enceladus' unusual brightness. Enceladus, it turns out, is covered in a 16-19 miles thick shell of highly reflective ice which hides a global saltwater ocean. The probe observed fissures in the ice of the moon's South Polar Terrain ejecting massive quantities of icy water into space. Some of the material forms Saturn's E ring.
Saturn's E ring is composed of material ejected from Enceladus as it orbits the gas giant. Enceladus is visible as the small black dot at the center of the image.NASA/JPL/Space Science Institute
Data from Cassini's Cosmic Dust Analyzer, or CDA, previously helped researchers identify organic compounds and other key building blocks for life within Saturn's E ring. Cassini also found material in the E ring that suggests hydrothermal activity deep within Enceladus.
"We suspect that so-called hydrothermal fields exist there - these are vents at the bottom of the ocean from which hot water rises. There is evidence that life on Earth originated in such fields," said lead author Nozair Khawaja, a research group leader at Freie Universität Berlin.
The new results come from data collected in a close flyby of Enceladus' icy plume, offering scientists a look at material that had been inside the moon just minutes before.
"The high-speed flyby of Enceladus enabled us to identify new compounds that were not found in the E ring data, most notably esters, alkenes and ether compounds," said Klenner, who helped validate the new CDA results. "Notably, esters and ethers can be part of lipids, and lipids are key to life as we know it."
The success of Cassini has helped stoke considerable investment in future missions to the outer solar system. NASA's Europa Clipper probe is currently en route to Jupiter to study its moon Europa, which is also a promising candidate in the search for extraterrestrial life.
This mosaic of Enceladus was built from a series of images captured by Cassini during a flyby that brought it within about 16 miles of the moon's surface.NASA/JPL/Space Science Institute
In the meantime, there's plenty more Cassini data up for grabs.
"It's phenomenal to continue learning from the Cassini mission," said Klenner, who will start a new position as an assistant professor at the University of California, Riverside in December. "Much of the CDA data still isn't analyzed and I'm so excited about what it may reveal next."
Co-authors include Frank Postberg, Thomas R. O'Sullivan, Maryse Napoleoni, Jon Hillier and Lucía Hortal Sánchez at the Free University of Berlin; Sascha Kempf at the University of Colorado, Boulder; Yasuhito Sekine and Maxwell Craddock at the Institute of Science Tokyo; and Jonas Simolka and Ralf Srama at the University of Stuttgart.
This research was funded by the European Research Council, the German Aerospace Center, the state of Berlin and NASA.
