NASA has announced that they have confirmation that Saturn’s moon Enceladus has a food source that could support potential microbial lifeforms. This crucial ingredient accompanies Enceladus’ grocery list of elements needed to support life: carbon, hydrogen, nitrogen, oxygen, organic molecules, and of course, liquid water.
"Almost all of the conditions that astrobiologists have identified for habitability are present on Enceladus: water, organics, and a chemical energy source," explains Hunter Waite, from the Southwest Research Institute. "The only things that are left on the checklist are phosphorus or sulfur."
This microbial food — the chemical energy source Waite is referring to — comes in the form of simple hydrogen. While this is the most abundant element in the known universe, it is typically found in the form of chemical compounds, such as the chemically-stable form of water. This hydrogen, however, is in its molecular form, being released from Enceladus’ hydrothermal vents. As a food source, hydrogen is consumed by some of Earth’s most primitive microbes: they combine it with carbon dioxide, to produce both energy and methane.
This setup is extremely familiar to researchers: hydrothermal vents in Earth’s oceans are host to their own miniature ecosystems, typically made up of organisms that don’t rely on sunlight to survive, drawing energy and warmth from the Earth’s interior instead. In the absence of any geothermal activity within the small moon, Enceladus’ heat enegy is theorized to be generated from tidal stresses produced from Saturn’s gravitational field.
The Cassini space probe sampled the hydrogen while it passed through plumes from the erupting geysers, dubbed "cryovolcanos", in October 2015, but it is just now that the readings have been verified by researchers. The delay in the confirmation was to make sure the sampled hydrogen actually came from Enceladus, and that it didn’t come from within Cassini’s Ion and Neutral Mass Spectrometer (INMS) sensor itself. As it winds down its 20-year mission, Cassini is scheduled to begin to de-orbit into Saturn later this month, as a safety precaution to avoid contaminating any potential lifeforms on Saturn’s moons with microbes from Earth.