The Ocean World Enceladus

Does life exist elsewhere in our solar system? This key question has been a major motivator for our exploration beyond Earth. Life as we know it requires liquid water, organic chemistry and energy. As Cassini discoveries have shown, all of these key ingredients appear to exist on Saturn’s tiny moon Enceladus, making it a possible habitat for life.NASA’s Cassini spacecraft arrived at Saturn in July 2004 and began making incredible findings in the Saturn system. Some of the most striking discoveries involved Enceladus. Only 300 miles in diameter, a huge plume of water ice and water vapor is erupting from a liquid water reservoir under Enceladus’ south pole. Jets and curtains of icy material shoot skyward from a series of four linear fractures nicknamed “tiger stripes”. Over the course of the next decade, Cassini repeatedly flew close to Enceladus and directly sampled its icy plume seven times. Cassini’s sensitive instruments discovered complex organic molecules, salts and silicates in the plume indicating that the water is in contact with a rocky core. We now know that the liquid reservoir underneath Enceladus’ icy crust is not a regional sea but a global, subsurface ocean. The ocean is salty, much like our own seas. Excess heat originates from the narrow tiger stripes and tiny silica nanograins in the plume provide evidence for hydrothermal activity on Enceladus’ seafloor. Similar hydrothermal systems on Earth support rich communities of life that contain organisms as large as tubeworms and crabs.With each discovery, Enceladus becomes an increasingly enticing astrobiology target. Could life exist in Enceladus’ ocean? A future mission may answer this question. Cassini was never meant to be a sea-faring mission, and while its instruments have helped answer important questions about the habitability of Enceladus, the question of whether life exists will require a more specialized set of instruments and a targeted mission. Enceladus’ lofting of free samples into space makes it a compelling destination.This research was performed at the Jet Propulsion Laboratory, California Institute of Technology (Caltech), under contract with NASA. Copyright 2016 Caltech. Government sponsorship is acknowledged.