Clipper has an impressive collection of remote sensing tools that will allow it to survey the ocean’s physical and chemical properties, even though it will never touch the moon itself. But almost all scientists expect that uncovering evidence of biological activity will require something to pierce through the ice shell and swim about in the ocean.
NASA/JPL-CALTECH
The good news is that any Europan life-hunting mission has a great technological legacy to build upon. Over the years, scientists have developed and deployed robotic subs that have uncovered a cornucopia of strange life and bizarre geology dwelling in the deep. These include remotely operated vehicles (ROVs), which are often tethered to a surface vessel and are piloted by a person atop the waves, and autonomous underwater vehicles (AUVs), which freely traverse the seas by themselves before reporting back to the surface.
Hopeful Europa explorers usually cite an AUV as their best option—something that a lander can drop off and let loose in those alien waters that will then return and share its data so it can be beamed back to Earth. “The whole idea is very exciting and cool,” says Bill Chadwick, a research professor at Oregon State University’s Hatfield Marine Science Center in Newport, Oregon. But on a technical level, he adds, “it seems incredibly daunting.”
Presuming that a life-finding robotic mission is sufficiently radiation-proof and can land and sit safely on Europa’s surface, it would then encounter the colossal obstacle that is Europa’s ice shell, estimated to be 10 to 15 miles thick. Something is going to have to drill or melt its way through all that before reaching the ocean, a process that will likely take several years. “And there’s no guarantee that the ice is going to be static as you’re going through,” says Camilli. Thanks to gravitational tugs from Jupiter, and the internal heat they generate, Europa is a geologically tumultuous world, with ice constantly fragmenting, convulsing and even erupting on its surface. “How do you deal with that?”
Europa’s lack of an atmosphere is also an issue. Say your robot does reach the ocean below all that ice. That’s great, but if the thawed tunnel isn’t sealed shut behind the robot, then the higher pressure of the oceanic depths will come up against a vacuum high above. “If you drill through and you don’t have some kind of pressure control, you can get the equivalent of a blowout, like an oil well,” says Camilli—and your robot could get rudely blasted into space.
Even if you manage to pass through that gauntlet, you must then make sure the diver maintains a link with the surface lander, and with Earth. “What would be worse than finally finding life somewhere else and not being able to tell anyone about it?” says Morgan Cable, a research scientist at NASA’s Jet Propulsion Laboratory (JPL).
Pioneering probes
What these divers will do when they breach Europa’s ocean almost doesn’t matter at this stage. The scientific analysis is currently secondary to the primary problem: Can robots actually get through that ice shell and survive the journey?