NASA's Europa Clipper mission, set to arrive at Jupiter's moon Europa in 2030, aims to scan the moon's icy surface and subsurface ocean for clues about its habitability. However, scientists are already looking ahead to advanced exploration tools, including SWIM robots that could one day dive directly into Europa's hidden seas.

SWIM envisions a swarm of cellphone-sized underwater robots delivered by a cryobot, which would melt through Europa's thick ice crust. Once deployed, these micro-swimmers would seek out temperature and chemical changes that could signal the presence of life.

"People might ask, why is NASA developing an underwater robot for space exploration?" said Ethan Schaler, principal investigator for SWIM at NASA's Jet Propulsion Laboratory (JPL). "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."

Testing the Waters
JPL engineers recently conducted more than 20 tests of SWIM prototypes in a 25-yard swimming pool at Caltech, as well as in specialized tanks. The 3D-printed robots, powered by small commercial motors, successfully demonstrated autonomous navigation, route correction, and precise exploration patterns. Remarkably, they even traced the letters "J-P-L" underwater.

One design, a wedge-shaped prototype, measured 16.5 inches (42 cm) long and weighed 5 pounds (2.3 kg). Spaceflight versions would be scaled down to palm-sized units, incorporating specialized parts and acoustic communication systems for underwater data transmission and positioning.

"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."

Simulated Missions
In addition to physical testing, researchers used computer simulations to evaluate how a virtual swarm of 5-inch-long (12-cm) robots would perform in conditions similar to Europa's subsurface oceans. These simulations informed the development of exploration algorithms and provided insights into tradeoffs between battery life, operational volume, and swarm size.

For instance, each robot could operate for up to two hours, collectively scanning about 3 million cubic feet (86,000 cubic meters) of water. The simulations helped optimize deployment strategies for maximizing data collection while conserving resources.

Multifunctional Sensors
A collaborative team at Georgia Tech has contributed an innovative ocean composition sensor for SWIM robots. This tiny chip, just a few millimeters square, can simultaneously measure temperature, pressure, pH levels, conductivity, and chemical composition. Such capabilities are vital for detecting the potential biosignatures needed to assess habitability.

Future Potential
While SWIM remains years away from being ready for space missions, the technology could find immediate applications here on Earth. "Schaler imagines SWIM robots potentially being further developed to do science work right here at home: supporting oceanographic research or taking critical measurements underneath polar ice."

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