All that life needs on Enceladus

Researchers believe life could exist on Saturn's moon Enceladus around hydrothermal vents which are similar to those found at the bottom of the Earth's ocean. Last week, NASA scientists published the results of their investigation in the journal Science.

"The abundance of H2, along with previously observed carbonate species, suggests a state of chemical disequilibria in the Enceladus ocean that represents a chemical energy source capable of supporting life", Jeffrey Seewald, a researcher at the Woods Hole Oceanographic Institution in MA who was not involved in the study, wrote in an accompanying "Perspectives" piece published alongside the new paper. The name comes from the byproduct - methane.

As belief systems go (and this is mine), this one is actually quite liberating once you accept it: Since we are unlikely to encounter any other life or life form than the ones we have now, we ought to make the most of what I call our One Orbit, our one life.

Cassini flew extremely near to Enceladus' surface to search for hydrogen specifically native to the moon, and operated INMS in a specific mode to minimize and quantify any misleading sources.

A discovery of molecular hydrogen was made in October 2015 - but has only now come to light - when NASA's Cassini spacecraft took samples as it passed 30 miles (49 km) above the moon's southern pole. And indeed, some methane was detected in the plume along with hydrogen and a lot of water.

The measurement was made using Cassini's Ion and Neutral Mass Spectrometer (INMS) instrument, which sniffs gases to determine their composition.

Cassini mission team associate Chris Glein added in a press conference, as quoted by the Daily Mail, that the data from Enceladus is especially interesting, as it now allows scientists to find out how much energy is generated by the moon's methanogenesis reactions. Enceladus is Saturn's sixth-largest moon.

To be habitable for life as we know it, a world must have water, an energy source, and the necessary chemical ingredients, such as hydrogen, carbon, nitrogen, oxygen, phosphorus, and sulfur.

The hydrothermal vents on Earth's ocean floor emit hot, mineral-laden liquid, allowing unique ecosystems - teeming with odd life forms - to thrive. Those reactions require hydrogen, which the authors explained is likely being continuously produced by subsurface reactions involving rock and hot water. The Hubble Space Telescope has observed what look to be plumes emanating from Europa. These images bolster evidence that the Europa plumes could be a real phenomenon, flaring up intermittently in the same region on the moon's surface. Pictured here, the textured surface of Enceladus is visible in the foreground, while rows of plumes rise from ice fractures in the distance. Researchers speculate that, like Enceladus, this could be evidence of water erupting from the moon's interior.

The detection of molecular hydrogen in the plume led to more analysis for broad identification of signals indigenous to Enceladus. "We discovered that Europa's plume candidate is sitting right on the thermal anomaly", said William Sparks of the Space Telescope Science Institute in Baltimore.

  • Carolyn Briggs