HOPPING may be the best way for robotic probes to explore the
surface of comets and asteroids. Japanese engineers have built a
cylindrical prototype that they say could take 9-metre hops in a
low-gravity environment. They propose adding a more advanced
version of the probe to MUSES-C, a Japanese mission to return an
asteroid sample to Earth in June 2006. Wheeled robots work well
on moons and planets, but the very low gravity of asteroids and
comets poses problems. The traction needed for horizontal motion
comes from the vehicle's weight pressing down on the surface,
but on an asteroid only 2 kilometres across the force of gravity
is about 100 000 times weaker than on Earth. That leaves so
little traction that the robot's wheels will slip unless they
move very slowly. Researchers at the Jet Propulsion Laboratory
in Pasadena, California, have already developed a wheeled rover
for MUSES-C, to ... To continue reading this article, subscribe
to receive access to all of newscientist.com, including 20 years
of archi