Nasa has designed a spacecraft filled with robotic hedgehogs that could be used to explore the moons of Mars.
Created by researchers at Stanford and MIT, the spikey, spherical rovers are designed to be deployed by a mother spacecraft above the surface before exploring the rocky, distant moon.
The robots, which are able half a metre wide, would "hop, tumble and bound across" the Martian moon Phobos, the researchers said in a press release.
They would operate without human control, and solve problems with wheeled craft like the Mars rover Curiosity, currently on the Red Planet's surface, which do not operate well in low gravity.
Three generations of prototype of the robots, named "hedgehogs", have already been created in the lab.
They would be deployed by a "Surveyor" spacecraft in orbit above the moon, after it completed a detailed survey of the terrain.
This coffee table-sized craft would fly around the lopsided moon powered by umbrella-shaped solar panels, monitoring the data sent back by the hedgehogs.
Each robot would be send down with gaps of a few days, allowing scientists to cover a wide area easily and quickly.
The system could also be used to explore asteroids and comets, the researchers said - all without human control.
"It's the next level of autonomy in space," said designer Marco Pavone, assistant professor at Stanford's Department of Aeronautics and Astronautics.
A mission to Phobos would focus on its composition and soil, in order to learn more about the history of the planet, the moon itself and the wider solar system.
Full tests could take place in two to four years, with a so-far unplanned mission at least a decade away.