NASA has tested a fleet of underwater robots designed to search for signs of life on distant ocean worlds. When NASA’s Europa Clipper arrives at Jupiter’s moon Europa in 2030, it will conduct 49 flybys to investigate whether the ocean beneath Europa’s icy crust could support life. Launched on October 14, the spacecraft carries cutting-edge instruments, but scientists are already envisioning next-generation robots capable of diving into Europa’s depths to extend the search. The vision includes the SWIM (Sensing With Independent Micro-swimmers) concept, which features a swarm of self-propelled, cellphone-sized robots. Delivered to subsurface oceans by an ice-penetrating cryobot, these robots could search for life-indicating chemical and temperature signals. “People might ask, why is NASA developing an underwater robot for space exploration? It’s because there are places we want to go in the solar system to look for life, and we think life needs water. So we need robots that can explore those environments — autonomously, hundreds of millions of miles from home,” said Ethan Schaler, SWIM’s principal investigator at NASA’s Jet Propulsion Laboratory (JPL). Recently, JPL tested SWIM prototypes in a Caltech swimming pool, achieving promising results. The 3D-printed plastic robots, equipped with off-the-shelf motors and electronics, demonstrated autonomous navigation, course correction, and an exploration pattern resembling a “lawnmower.” They even spelled out “J-P-L” during testing. For safety, the robots were tethered to a fishing line, with an engineer on standby. Over 20 test rounds were conducted at the pool and in JPL’s lab tanks, refining designs and capabilities. “It’s awesome to build a robot from scratch and see it successfully operate in a relevant environment,” Schaler said. “Underwater robots in general are very hard, and this is just the first in a series of designs we’d have to work through to prepare for a trip to an ocean world. But it’s proof that we can build these robots with the necessary capabilities and begin to understand what challenges they would face on a subsurface mission.” The wedge-shaped prototype tested in the pool was 16.5 inches long and weighed 5 pounds. Space-ready versions would be about three times smaller, featuring miniaturised components and a wireless underwater acoustic communication system for data transmission and positioning. In addition to physical tests, digital simulations mimicked Europa’s pressure and gravity conditions. These virtual experiments guided the development of algorithms to optimise the robots’ exploration strategies, balancing battery life, exploration volume, and swarm size. For instance, a dozen 5-inch-long robots operating in waves could explore about 3 million cubic feet of water within two hours. Collaborators at Georgia Tech also developed a multi-sensor chip, capable of measuring temperature, pressure, pH, conductivity, and chemical composition. This breakthrough, just millimeters in size, integrates all these sensors into a single package. Though years of development remain before these robots could be mission-ready, Schaler envisions future SWIM robots contributing to oceanographic research and polar ice exploration on Earth. When: 21 Nov 2024 Credit: NASA/JPL-Caltech/Cover Images **EDITORIAL USE ONLY. MATERIALS ONLY TO BE USED IN CONJUNCTION WITH EDITORIAL STORY. THE USE OF THESE MATERIALS FOR ADVERTISING, MARKETING OR ANY OTHER COMMERCIAL PURPOSE IS STRICTLY PROHIBITED. MATERIAL COPYRIGHT REMAINS WITH STATED PHOTOGRAPHER AND/OR SUPPLIER.**