Enceladus Life Finder: Search for Life in a Habitable Moon.

Abstract:

A thousand times smaller in mass than Ganymede, Enceladus was known from Voyager data to be extremely bright and a dearth of craters on some parts of its surface suggested geologic activity. Cassini discovered the presence and composition of a plume erupting from the south polar terrain of Enceladus, approximately 100 narrow, distinct “geysers” or “jets” that feed it, and anomalous thermal signatures along fractures from which the geysers erupt. Cassini discovered organic and nitrogen-bearing molecules in the plume vapor, and detected salts in the plume icy grains, arguing strongly for ocean water being in contact with a rocky core. As much as Cassini has done, it cannot tell us whether the ocean of Enceladus hosts an active biota today. Enceladus Life Finder (ELF) is a Discovery-class solar-powered Saturn orbiter designed to fly multiple times through the plume of Enceladus. It carries two state-of-the-art mass spectrometers designed to analyze the gas and grains in the plume. The goals of the mission are derived directly from the most recent decadal survey: first, to determine primordial sources of organics and sites of organic synthesis today, second, to determine if there are modern habitats in the solar system beyond Earth where the conditions for life exist today and third, if life exists there now. ELF conducts three tests for life. The first test looks for a non-abiotic distribution of amino acids, the second determines whether the carbon number distribution in fatty acids or isoprenoids is biased toward a particular rule, and the third measures carbon and hydrogen isotopic ratios, together with the abundance of methane relative to other alkanes, to assess whether the values fall in the range for biological processes. The ELF mission spacecraft conducts ten science plume fly-throughs; the baseline science is completed in the first five plume passages.