Pluto-Bound Probe Passes Mars’ Orbit
To be dispatched early 2006, the outward bound New Horizons spacecraft will throw new light on distant Pluto and its moon, Charon, as well as Kuiper Belt objects. Image
Credit: Dan Durda

NASA's New Horizons probe has left the inner planets of the Solar System behind as it streaks toward a rendezvous with Pluto and its moons.

The spacecraft, billed as NASA's fastest-flying probe, hurtled past the orbit of Mars - though not the planet itself - Friday on its way towards a Jupiter flyby and its more distant target Pluto.

"It's pretty amazing," New Horizons principal investigator Alan Stern told "It's a straight line across the Solar System. There are hardly any curves because this is so fast."

New Horizons sped past Mars' orbit some 151 million miles (243 million kilometers) from the Sun at a rate of about 13 miles (21 kilometers) per second. The red planet, however, trailed behind the spacecraft at a distance of about 186 million miles (299 million kilometers), mission managers said, adding that New Horizons was closer to Earth than Mars.

NASA launched New Horizons, a piano-sized spacecraft weighing about 1,054 pounds (478 kilogram), atop a Lockheed Martin-built Atlas 5 rocket - its most powerful booster - to fling the Pluto-probe spaceward on Jan. 19, 2006.

Six of the probe's seven science instruments have already been checked for their health as the spacecraft heads towards Jupiter, where it will use the giant planet's gravity to boost its way on to Pluto and the icy object-filled Kuiper Belt.

But first, the spacecraft must pass through the Asteroid Belt, which despite its reputation is primarily made up of empty space rather than a teeming rock field, mission managers said.

"We won't be hit," said Stern, the executive director of the space science and engineering division at the Southwest Research Institute in Boulder, Colorado. "We won't even come close enough to make any useful science observations of asteroids. They're really very far apart."

New Horizons is expected to fly past Pluto and its moons July 2015. The spacecraft is due to make its closest approach to Jupiter on Feb. 28, 2007.