A new report published by NASA today says that the Cassini space probe has found evidence that hydrogen gas exists on the Saturnian moon Enceladus. The finding adds to the idea that the moon might harbor life in its subsurface ocean, as microbes could dine on the gas, along with carbon dioxide dissolved in the water to create energy, through a process known as methanogenesis. Plus, Hubble spies a plume on Europa for the second time.
In deep thermal vents beneath the oceans here on Earth known as "white smokers," hydrogen gas is formed through interactions between the heated water and surrounding rock. The Cassini mission has already helped scientists reach the conclusion that hot ocean water beneath Enceladus' icy crust is coming into contact with a rocky core, so the new findings support the idea that a similar process is at play on the moon in terms of the formation of hydrogen.
"Although we can't detect life, we've found that there's a food source there for it. It would be like a candy store for microbes," said Hunter Waite, lead author of the study appearing today in the journal Science.
The probe found the hydrogen when it made its last and closest pass through plumes at Enceladus' south pole on Oct. 28, 2015. From that pass and previous observations using the Cassini's Ion and Neutral Mass Spectrometer (INMS) instrument – which basically acts like a chemical nose to sniffs gases – the instrument found that the plumes contain about 98 percent water, one percent hydrogen and that the final percent consisted of a mixture of other molecules including carbon dioxide, methane and ammonia.
"Life as we know it requires three primary ingredients: liquid water; a source of energy for metabolism; and the right chemical ingredients, primarily carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur," says NASA. "With this finding, Cassini has shown that Enceladus – a small, icy moon a billion miles farther from the sun than Earth – has nearly all of these ingredients for habitability. Cassini has not yet shown phosphorus and sulfur are present in the ocean, but scientists suspect them to be, since the rocky core of Enceladus is thought to be chemically similar to meteorites that contain the two elements."
While the Enceladus finding is intriguing on its own, NASA also released a paper today detailing the fact that the Hubble Space Telescope has again found plumes jetting off of Jupiter's moon Europa in the same location one was spotted on in 2014. The original plume was estimated to be about 30 miles (50 km) high, while the newly imaged jet extended about 62 miles (100 km) above the moon's surface. Both plumes were found above a region of unusual warmth and cracks in Europa's crust spotted by the Galileo probe in the 1990s. The fact that Hubble has seen them twice has led NASA to believe that they might be part of a regular lunar feature and quite possibly be evidence of water vapor eruptions.
NASA says the discovery will help it to better equip the Europa Clipper mission set for the 2020's when a probe will visit the moon to examine the plumes.
"If there are plumes on Europa, as we now strongly suspect, with the Europa Clipper we will be ready for them," said Jim Green, Director of Planetary Science, at NASA Headquarters.
The following video dives into more details about the Hubble find.