Spike-Covered "Hedgehog" Probes Could Explore Mars Moon Phobos

NASA scientists are working on a new kind of "hedgehog" shaped rover to explore Phobos, one of the tiny moons of Mars.

The spiky-legged robots are about a foot and a half in diameter and are uniquely equipped to roam across the low-gravity environment of the Martian satellite. With an average diameter of only about 14 miles, the roughly-shaped Phobos has gravity 1,000 times weaker than Mars, or about 2,600 times weaker than the Earth.

That means traditional rovers would have a hard time getting traction against the powdery regolith. Instead of pushing forward, they might float gently on the surface spinning their tires.

The pointed spines of the hedgehog rovers allow them to skip along the surface, avoiding both thick dust and rocky terrain.

Three inertial discs power each robot -- one for each direction. A slight spin provides enough momentum to move the rover in a particular direction in the absence of an atmosphere, sending the robot tumbling along on its spines.

Quick acceleration of the discs allows the rover to hop, and a fast spin creates a leap.

Several rovers can be remotely operated by a coffeetable-sized mothership called the Surveyor that remains in orbit.

The Surveyor would deploy one rover at a time every few days in separate locations across the surface of Phobos. The mothership communicates remotely with the rovers, then relays instructions and data back to Earth.

As NASA contemplates a manned mission to Mars, advance preparation is imperative. Phobos offers unique opportunities to study Mars without many of the drawbacks of dealing with a planet-sized celestial body.

Scientists are still in disagreement about the origin of Phobos. It may be a captured asteroid, but it may be more similar to Earth's moon, which is likely made up of material from the planet ejected into space after a massive collision.

If Phobos is indeed ejected material, its composition should be similar to that of Mars itself. And with its low gravity, it is much easier to send probes to Phobos to gather data, and possibly even return them, than it is to land on and take off from Mars.

Phobos could also provide a staging ground for excursions to the planet below. A base established on Phobos could offer shorter and less harrowing trips to Mars while still being supplied from Earth.

Development of the rovers is still in progress, and scientists expect it may be a decade or more before a mission to Phobos is possible. Add in the two-year travel time and the current crop of Mars rover scientists could be retired and watching breathlessly with the rest of the world when the little hedgehogs finally touch down.