Mars probe drifts into retirement as fuel runs out

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Space experiment team end three months of bedrest

A pioneering space probe that demonstrated the power of human ingenuity in the face of extreme adversity will drift into retirement today when its revolutionary engines run out of fuel.

Deep Space 1 was designed to test a dozen new technologies for space exploration – including an "ion thruster" engine more suited to Star Trek than Nasa – but fell victim to a potentially devastating technical failure early in its life.

Despite losing its navigation camera, the probe was still able to complete its mission as well as making an unscheduled rendezvous with a comet, with Nasa engineers skillfully guiding the blinded probe through millions of miles of space.

Deep Space 1 was launched in 1998 and is only the second spacecraft to fly past a comet when it took photographs of Comet Borrelly in a last-minute mission that Nasa engineers believe set a new precedent in space exploration.

Marc Ryman, the probe's project manager at Nasa's Jet Propulsion Laboratory in Pasadena, California, said: "I think there are several legacies of Deep Space 1.

"Because of Deep Space 1's technology testing, many future missions that would have been unaffordable or even impossible now are feasible," Dr Ryman said.

Following the failure of the navigation camera, which mapped the position of the stars to steer the probe, engineers on the ground reprogrammed the on-board computers to use a smaller, technically inferior camera for the same job. Nasa says that the technical challenge involved was reminiscent of the film Apollo 13, where one of the characters dumps a sack of items on a table and asks Nasa engineers to remedy a build-up of dangerous gas in the spacecraft.

After reprogramming Deep Space 1's computers, the probe successfully tracked, intercepted and took pictures of Comet Borrelly, a relatively unknown comet discovered nearly a century ago.

"We learned a great deal about comets with the encounter, and the fantastically rich science data from Borrelly will be the basis for much of the scientific work on comets for years to come," Dr Ryman said.

The experimental ion-thruster engines, which are due to run out of fuel today, enabled the spacecraft to achieve speeds approaching 4.5 kilometres a second (10,000mph). The engines worked by imparting electrical charges to atoms of xenon gas and accelerating the charged particles to 30km per second to produce an "exhaust" similar to rocket propulsion.

Pictures taken from the craft revealed that the five-mile-long core of Comet Borrelly is a rich landscape of mountains, valleys and plains. The probe also discovered that the comet absorbs about 98 per cent of the sunlight reaching it, making it one of the darkest known objects in the solar system.