How can we learn if a tunnelbot powered by nuclear reactors finds life under Europa’s icy crust and how can scientists back on Earth contact a submerged probe? We know very little about the composition of that ice, its thickness, or the existence of any water pockets within it. It’s as hard as granite, and we have no idea how thick it is.
Ocean moons like Europa and Enceladus orbiting Jupiter and Saturn, respectively, show intriguing signs of potential habitability. Europa’s thin atmosphere, detected by the Hubble Space Telescope, contains a steady stream of water vapor, which must have a source. Through its studies of Jupiter’s system from 1995 to 2003, NASA’s Galileo mission concluded that Europa has a subsurface ocean containing more water than all of Earth’s oceans put together. And it’s salty water, too.
Europe has an icy exterior as tough as granite. Robotic exploration of Europa’s ice could take years. The icy moon hides an ocean. A nuclear-powered cryobot is the best option for tunneling through all that ice. Cryobots and landers would be linked by cable. Once it made it into the water, it could begin collecting information. Cryobots, which would release a swarm of tiny robots to take in-situ measurements across a larger area, are another possibility for improving sampling rates.
It’s possible that the tunneler will come across pools of liquid water en route, which would speed things up, but ultimately reaching the ocean is the objective. How will the mission control team stay in touch with it as it makes its long journey? As they descended, how would the robot(s) coordinate their movements with each other?
A workable plan would involve the robot operating beneath the ice making contact with a lander, which would then upload the data at regular intervals to a spacecraft orbiting Jupiter, which would then make contact with Earth.
However, a major hurdle remains in terms of data transfer between the lander and the subterranean robot. Europa’s surface is the smoothest of any Solar System body, but the moon’s has relatively few craters visible in images. What this means is that tectonic activity is constantly resurfacing it. Therefore, the icy crust that surrounds Europa is not calm. When the ice is stressed, shifts, and shakes, how can a tunneling cryobot talk to a lander over a tether? If the tether is broken or severed, the mission is doomed.
Testing new equipment
The Signals Through the Ice (STI) group is here to help. They are attempting to modify polar exploration-style fiber optic tethers for use on Europa. The polar regions of Europa are much colder than those of Earth. The ice on Europa could have a temperature anywhere from 100 to 260 Kelvin.
The heat isn’t the only issue. It’s likely that the ice will shift, rub against itself, and undergo shearing. A communications cable must be able to handle whatever Europa throws at it, or the entire mission could fail.
The STI group put their tether prototype through its paces under “Europa” like conditions. The tether has commercial-grade optical fiber placed between two layers of crush protection and a layer of kevlar. Tethers like these are currently in use on ocean submersibles here on planet Earth.
Although the cables served their purpose well, they were far from flawless. They were able to transmit data continuously during the simulated conditions, albeit with some signal degradation. One of the cables had some minor exterior damage in the coldest conditions as well. The fact that data transmission continued even after the cables’ outer layer was damaged is encouraging, though the design is far from perfect.