What NASA’s Cassini spacecraft found “would be like a candy store for microbes,” said Hunter Waite, lead author of the new study out this week. In October 2015, Cassini conducted one of many close flybys of Enceladus. This flyby took the spacecraft just 30 miles above the moon’s surface. And straight through a plume of water erupting from the moon’s south pole.
Cassini’s Ion and Neutral Mass Spectrometer (INMS) instrument got a good whiff of the plume’s material and noticed molecular hydrogen. Observations made by INMS show the gas plume is made up of 98% water and about 1% hydrogen. The last 1% is a mix of carbon dioxide, methane and ammonia.
Hydrogen is the big news here. It doesn’t confirm life. But Linda Spilker, Cassini project scientist at NASA’s JPL, explains why it’s still a big deal. “Confirmation that the chemical energy for life exists within the ocean of a small moon of Saturn is an important milestone in our search habitable worlds beyond Earth,” says Spilker.
You can’t just discover hydrogen and make the leap to life. What hydrogen does is tease us that something is going on beneath the cold, icy surface of Enceladus. Scientists believe the most likely source of the hydrogen is chemical reactions between water and silicate rock (hydrothermal activity). Enceladus’ ocean floor is likely home to hydrothermal vents like the ones we see on Earth.
The big question scientists still can’t answer is are these vents home to microbes as they are on Earth? We only have life on Earth to go by as we search for it beyond. In our deep oceans, molecular hydrogen ocean serves as a food source for microbes. They eat the hydrogen and turn it into methane.
These vents on Earth are nicknamed White Smokers (and Black Smokers). Here are a couple near the Galapagos Islands.
What this week’s findings show is more evidence hydrothermal activity is happening in the interior of Enceladus. The ingredients are here for life. There’s water, a source of energy and the right chemical ingredients. Unfortunately, Cassini can’t detect life. It was never designed to. Hell, we didn’t even know these plumes existed until Cassini reached the Saturn system in 2005.
Another mission to Enceladus?
There is a proposed astrobiology mission dubbed the Enceladus Life Finder, or ELF. Its primary objective would be to search for biosignatures and biomolecules in the plumes of Enceladus. Instruments onboard the spacecraft would measure amino acids, fatty acids and figure out if methane found in plumes is being produced by living organisms
Enceladus is a fantastic target because we don’t have to get to the ocean. The ocean comes to us. We don’t need to send drilling equipment. We just need a spacecraft with the right instruments to fly through the water plumes.
NASA sums it up best on the question of life on Enceladus and elsewhere. “But if life is there, that means life is probably common throughout the cosmos; if life has not evolved there, it would suggest life probably more complicated or unlikely than we have thought. Either way, the implications are profound.”
The next slate of missions might finally give us a definitive answer. Technology today is leaps and bounds better than it was in the 90s when the Cassini mission launched.