Swarm of tiny swimming robots could search for life on distant worlds

One day, a swarm of robots the size of a cell phone could fly through the water beneath the miles-thick icy shell of Jupiter’s moon Europa or Saturn’s moon Enceladus, looking for signs of alien life. Wrapped in a narrow ice-melt probe that would tunnel through the frozen crust, the tiny robots would be released underwater, swimming far from their parent vessel to measure the size of a new world.

That’s the vision of Ethan Schaler, a robotics mechanical engineer at NASA’s Jet Propulsion Laboratory in Southern California, whose Sensing With Independent Micro-Swimmers (SWIM) concept recently received $600,000 in Phase II funding from the NASA Innovative Advanced Concepts (NIAC) program. The funding, which follows his 2021 award of $125,000 in Phase I NIAC funding to study feasibility and design options, will allow him and his team to create and test 3D-printed prototypes over the next two years.

An important innovation is that Schaler’s mini-swimmers would be much smaller than other concepts for planetary ocean exploration robots, allowing many to be loaded compactly into an ice probe. They would add to the probe’s scientific reach and could increase its chances of detecting evidence of life while assessing the potential habitability of a distant ocean-bearing celestial body.

“My idea is, where can we take miniaturized robotics and apply them in interesting new ways to improve our solar systemSchaler said. “With a swarm of small swimming robots, we can explore a much larger volume of ocean water and improve our measurements by having multiple robots collect data in the same area.”

The early-stage SWIM concept is not yet part of a NASA mission and envisions wedge-shaped robots, each about 12 centimeters long and about 60 to 75 cubic centimeters in volume. About four dozen of them could fit into a 4-inch-long (10 centimeters long) section of a 10-inch (25-centimeter) diameter cryobot, which takes up about 15% of the scientific payload volume. That would leave plenty of room for more powerful but less mobile scientific instruments that could collect data during the long journey through the ice and provide stationary measurements in the ocean.

The Europa Clipper mission, scheduled for a 2024 launch, will collect detailed science during multiple flybys with a large array of instruments when it arrives at Jupiter’s moon in 2030. Looking further into the future, cryobot concepts to explore such ocean worlds are being developed through NASA’s Scientific Exploration Subsurface Access Mechanism for Europe (SESAME) program, as well as through other NASA technology development programs.

better together

As ambitious as the SWIM concept is, the aim would be to reduce risk while improving science at the same time. The cryobot would be connected via a communications cable to the surface lander, which would in turn be the point of contact with mission controllers on Earth. That connected approach, along with the limited space to accommodate a large propulsion system, means the cryobot probably won’t get much further than the point where ice meets the ocean.

“What if, after all the years it took you to get into an ocean, you get through the ice shell in the wrong place? What if there are signs of life there, but not where you entered the ocean?’ said SWIM team scientist Samuel Howell of JPL, who also works on Europa Clipper. “By bringing these swarms of robots with us, we could look ‘there’ to explore much more of our environment than a single cryobot would allow.”

Howell compared the concept to NASA’s Ingenuity Mars Helicopter, the airborne companion of the agency’s Perseverance rover on the Red Planet. “The helicopter increases the range of the rover and the images it returns are context to help the rover understand how to explore its environment,” he said. “If you had a couple instead of one helicopter, you would know a lot more about your environment. That’s the idea behind SWIM.”

SWIM would also allow data collection away from the cryobot’s red-hot nuclear battery, which the probe would rely on to melt a downward path through the ice. Once in the ocean, that heat from the battery would create a thermal bubble, slowly melting the ice above it, potentially triggering reactions that could alter the water’s chemistry, Schaler said.

In addition, the SWIM robots could converge in a behavior inspired by fish or birds, reducing errors in data due to their overlapping measurements. That group data can also show gradients: temperature or salinity, for example, increasing across the swarm’s collective sensors and pointing to the source of the signal they’re detecting.

“If there are energy gradients or chemical gradients, that’s how life can arise. We’d have to get upstream from the cryobot to feel those,” Schaler said.

Each robot would have its own propulsion system, on-board computer and ultrasonic communication system, along with simple sensors for temperature, salinity, acidity and pressure. Chemical sensors to check for biomarkers – signs of life – will be part of Schaler’s Phase II study.

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