The clues are in tiny grains of rock found near Saturn over a decade ago. In recent years, scientists have found that the microscopic grains are mostly made up of silica, which is found on Earth in sand. They were incredibly uniform in size, suggesting that some unusual process must have formed them.
According to a research team lead by Sean Hsu, a research associate at the University of Colorado at Boulder's Laboratory for Atmospheric and Space Physics, hydrothermal vents in Enceladus's ocean are the most likely culprit.
"We methodically searched for alternate explanations for the nano-silica grains, but every new result pointed to a single, most likely origin," Frank Postberg, a Cassini CDA team scientist at Heidelberg University in Germany and study co-author, said in a statement.
We already suspect, based on gravitational analysis of the moon, that there's liquid water sloshing around between the icy surface of Enceladus and the rock down below. But for such uniform particles of silica to form, Hsu said, there must be hot water -- nearly 200 degrees Fahrenheit -- coming up from deep within the planet and interacting with the cold of the surface.
"Basically, we think that hot water interacting with rocks leeches out silica," Hsu told The Post, "And as the temperature drops, nanoparticles start to form. Depending on the condition of the silica solution, the particles will form at very particular sizes, like the ones we've detected."
If Saturn's moon really is undergoing these processes, then it could have the ingredients necessary to make life. That doesn't mean it's actually following the recipe.
"Without sunlight there to provide energy for life, you need something like hydrothermal systems," Hsu explained. "They provide energy and warmth, they leech minerals out from rock, and of course they involve liquid water -- so the basic building blocks are all there. But of course that's not a guarantee."
Even if the hydrothermal vents are there, Hsu said, we don't know how long they've been there.
"Life needs a really stable environment to evolve in, for a long time," he said. "And we don't know how stable this is, or for how long."
But he hopes that his analysis will motivate further exploration of Saturn and its moons. And by comparing the hydrothermal activity with that on Earth, he said, we could come to some understanding as to why one supported life while the other didn't.