SWIM / NASA-funded concept; larger prototypes tested on Earth

An alien-ocean mission rehearsed in a swimming pool

NASA/JPL-Caltech

The next place a space robot explores might require propellers instead of wheels. SWIM, short for Sensing With Independent Micro-swimmers, imagines dozens of tiny robots released into an ocean beneath an icy moon. A separate cryobot would first melt through the crust, then send the swimmers out to investigate water beyond its immediate surroundings.

Spreading out matters. Several robots could compare temperature and chemical measurements across an area, follow interesting variations, and check one another's readings. The concept gives each swimmer its own propulsion and computer, with sound carrying information through the water. This is exploration by a group of small scouts, designed to gather a broader picture than one stationary instrument could provide.

In 2024, JPL engineers tested larger prototypes in a Caltech swimming pool. One navigated an overlapping survey pattern autonomously and even traced the letters J, P, and L. An engineer followed with a fishing line in case it needed rescuing. The pool robots were much larger than the envisioned space versions, and an icy-moon mission would require substantial further development. Still, that ordinary pool became a place to test an extraordinary idea: sending a robotic school of swimmers into another world's ocean.