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Big ball would make Mars study a breeze

Artist's concept of the 'tumbleweed rover' on Mars.
Artist's concept of the 'tumbleweed rover' on Mars.  

By Richard Stenger

(CNN) -- A spherical probe as tall as a house could use the natural winds on Mars to propel itself around the red planet, rolling like a giant tumbleweed over boulders instead of sidestepping them like conventional rovers, according to NASA scientists.

Lightweight and inflatable, the rolling robot could carry cameras and water-seeking instruments in its interior, tethered in place by tension cords.

When it reached a spot of particular interest, the ball could partially deflate to stop, then re-inflate once it wrapped up its close-up observations, said scientists working on a prototype at NASA's Jet Propulsion Laboratory in Pasadena, California.

JPL researchers came up with the idea after another experimental rover failed during testing. Dozing through the Mojave Desert, the prototype lost one of its shoulder-high, inflatable tires, which then sped fast and far along the sand dunes.

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"It went a quarter mile in nothing flat," said NASA technician Tim Conners, who chased down the freewheeling sphere in an all-terrain vehicle.

NASA scientist Jack Jones was amazed. "The ball went up steep, steep cliffs of sand. Nothing stopped it."

Jones and his colleagues at JPL's Inflatable Technology for Robotics Program were inspired. "If we make these things big enough, nothing will stop one," he said.

The rolling Mars robot could reach speeds of 35 km/h (22 mph) and come to a halt by releasing gas.
The rolling Mars robot could reach speeds of 35 km/h (22 mph) and come to a halt by releasing gas.  

Testing a 1.5-meter (5-foot) ball in the desert, the researchers determined that a sphere four times that size could climb over sizeable rocks and roll up slopes with an incline of more than 25 degrees, using only the thin, but robust, winds of Mars.

To help control the direction, the ball could deflate during unfavorable winds, or use an internal guidance system that pumps fluids to the left or right, coaxing the sphere to move in one direction or another.

"This is experimental, so we're trying different things. But I'm pretty confident that it will work," Jones said.

More Mojave tests in late August were expected for the tumbleweed rover. The scientists think such a probe could use its own natural bounce to cushion a landing on Mars or other bodies in the solar system with favorable atmosphere and gravity conditions, possibly Neptune's moon Triton or Jupiter's moon Io.

• NASA Jet Propulsion Laboratory
• JPL: Inflatable Rover Program

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