Nasa plans Neptune landing Planet's moon Triton may hold secrets of

AUDACIOUS plans for a 30-year space mission to land a probe on Neptune and its largest moon, Triton, are being developed by a team of US researchers backed by Nasa.

The team, comprising a university professor and a robotic systems expert, have come up with a concept for a 36-tonne "mothership" powered by a nuclear fission reactor and ion propulsion system and equipped with probes that would investigate the ice giant orbiting some 4.5 billion kilometres from the Sun.

The real scientific lure of a mission to Neptune, the eighth planet from the Sun, lies with Triton. Only one spacecraft, Voyager 2, has visited Neptune and, during a flyby in 1989, it found that Triton has a surface of fascinating contrasts and geysers of nitrogen. It is thought to be a captured object which came in from the furthest reaches of the solar system, rather than a natural satellite.

"The moon is geologically active - we've seen that from Voyager 2's pictures of geysers, " explained David Atkinson, a University of Idaho professor.

"It's just so different to all the other moons of Neptune, and the moons of Uranus and Jupiter, and it would make an excellent comparison with Kuiper Belt objects such as Pluto and its moon, Charon.

"It would provide us with a wealth of information about the origin and evolution of the outer solar system."

Atkinson and his colleague Bernie Bienstock, a robotic systems project manager with aerospace company Boeing, put their concept together under a Nasa Vision contract, which aims to help researchers investigate possible missions.

The team presented their concept last week during the American Geophysical Union Fall Meeting in an attempt to rally support for the plan.

They hope it could become one of the US space agency's flagship missions, of the type Nasa can fly only once adecade because of the scale and cost involved.

According to their concept, which could cost dollars-3bn-dollars- 4bn and probably need international partners, the mothership would send two probes on a collision course with Neptune to take readings in the atmosphere before being crushed by its pressure. The mothership would then attempt to put a lander on the surface of 2700km-wide Triton.

Voyager showed Neptune to be a blue giant with an extremely dynamic atmosphere. Its winds race around the planet at speeds of 300 meters per second. Voyager also pictured its "great dark spot", a storm system akin to Jupiter's.

Touching down safely would be a colossal engineering challenge, Bienstock concedes.

"There is a very thin atmosphere on Triton, but there's not enough for parachutes to slow you down. You've got a lot of engineering overhead just to deliver the science package."

alan. crawford@sundayherald. com

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