Some day in the future, a swarm of cellphone-size robots could swim through the water beneath the kilometres-thick icy shell of Jupiter’s moon Europa or Saturn’s moon Enceladus, looking for alien life. These robots could be packed within narrow ice-melting probes that would tunnel through the frozen crust to release the tiny robots underwater, which can then swim far and deep to learn about the new worlds.
Or at least, that is the vision of Ethan Schaler, a robotics mechanical engineer at NASA’s Jet Propulsion Laboratory (JPL) in Southern California. Schaler’s Sensing With Independent Micro-Swimmers (SWIM) concept was recently awarded $600,000 in Phase II funding from the NASA Innovative Advanced Concepts (NIAC) program. Schaler and his team will use the funding to make and test 3D-printed prototypes over the next two years.
SWIM’s early-stage concept envisions wedge-shaped robots, each about 12 centimetres long and 60 to 75 cubic centimetres in volume. They are designed so that about four dozen of them could fit in a cryobot (ice-penetrating probe) 25 centimetres in diameter, taking up just 15 per cent of the science payload volume. This would leave more room for more powerful but less mobile science instruments that could gather data through stationary measurements of the ocean.
Each robot would have its own propulsion system, onboard computer, and ultrasound communications system, along with sensors for temperature, salinity, acidity and pressure. Phase II of the study will also add chemical sensors to monitor for biomarkers.
NASA’s Europa Clipper mission, planned for a 2024 launch, will do multiple flybys of Jupiter’s moon to gather detailed data with a large suite of instruments when it arrives there in 2030. Cryobot concepts to investigate such ocean worlds are being developed through NASA’s Scientific Exploration Subsurface Access Mechanism for Europa (SESAME) program, as well as through other NASA technology development programs.
The cryobot that deploys the swimming robots would be connected to the surface-based lander through a communication tether. The surface-based lander, in turn, would be the point of contact with mission controllers on Earth. This tethered approach means that the cryobot would probably be unable to venture much beyond the point where ice meets the ocean.
“What if, after all those years it took to get into an ocean, you come through the ice shell in the wrong place? What if there’s signs of life over there but not where you entered the ocean?By bringing these swarms of robots with us, we’d be able to look ‘over there’ to explore much more of our environment than a single cryobot would allow,” said SWIM team scientist Samuel Howell of JPL, in a press statement.
Howell compares the swimming robots to NASA’s Ingenuity Mars Helicopter, the Perseverance rover’s airborne companion on Mars. The helicopter extends the reach of the rover and sends images back, helping the rover understand how to explore its environment. In this case, the multiple swimming robots can be thought of as multiple helicopters exploring areas around the cryobot to send back data.
Also, the cryobot will have a nuclear battery, which it will rely on to melt a downward path through the ice. Once in the ocean, that heat could create a thermal bubble, slowly melting the ice above and causing reactions that could change the water’s chemistry. SWIM would allow the collection of data far away from this.
Further, the SWIM robots could mimic fish and birds to “flock” together and take overlapping measurements to reduce errors in the data. This group data could also show gradients: temperature or salinity. For example, the swarm’s collective sensors could be used to identify the source of a temperature or salinity change and point in that direction for further exploration.
“If there are energy gradients or chemical gradients, that’s how life can start to arise. We would need to get upstream from the cryobot to sense those,” said Schaler in a press statement.