Alien microbes could, in theory, feast beneath the icy surface of Saturn’s moon Enceladus. In April, astronomers reported that the Cassini spacecraft had discovered a chemical brew erupting from Enceladus’ oceans — the same kind that bacteria eat at Earth’s hydrothermal vents. Discover talked with Hunter Waite, Cassini researcher and NASA’s program director of space science and engineering, to take us there.
Q: What did we know about Enceladus before Cassini?
A: We knew nothing. We didn’t know anything about the vents. We didn’t know anything about the global ocean. We knew it was a small, icy moon in the Saturn system. But the Saturn system is full of small, icy moons.
Q: What would it be like flying along with Cassini over Enceladus?
A: The action happens pretty fast because you’re traveling at 7 or 8 kilometers per second. And [Enceladus] is pretty small — it's like the size of Arizona.
You’re getting pummeled by these little ice grains. As you’re flying over, you’ll see these geological features, these scars — little channels, basically — what we call the “tiger stripes.” Within those tiger stripes are the vents, straight from the global ocean. And above the surface of the ocean, a splash comes up — you can imagine a splash from a wave — that will instantly freeze. That’s what creates these grains. These have information about the salt content of the ocean and some of the organics that are present there.
Q: How close did Cassini get?
A: We went really close. It was about 50 kilometers — the closest flyby over the tiger stripes. We could look at the chemical balance and determine that the [hydrogen] we saw was sufficient to provide food for microbes. The obvious message is let’s go back and try to find life.
Q: At this point, would you be surprised if we didn't find life on Enceladus?
A: I would be a bit surprised, yes. But I would be happy to find the answer one way or the other because I think both — whether you find it or not — will lead to a better understanding of how life arose on Earth and what it really means.