An ambitious plan to fly an aircraft in the Martian atmosphere is one project the American space agency Nasa has requested funding for in its new budget.

Watch the Mars airplane deploy its wings

The flight would take place in 2003, a hundred years after the Wright brothers' first historic flight.

The plan is for the robot aircraft to be sent to Mars on a European Ariane 5 rocket. It would enter the Martian atmosphere inside a heat shield which would then drop away.

Parachutes would slow it down to allow large wings to unfold. It would fly over Mars' desert landscape for a few days.

Future landing sites

The proposed flight path over the Valles Marineris - the middle leg is 600km

The aircraft is part of Nasa's micromission programme. It would carry out an airborne survey of Mars looking for a landing site for a future sample mission. It would also explore geologically interesting and dramatic areas.

NASA already has a design for the aircraft, which will have to weigh no more than 205kg (450lbs). It will have a budget of just $50 million and will be one of Nasa chief Dan Goldin's "faster, better, cheaper missions".

"This is going to be an incredible achievement," Goldin said.

Building an aircraft to fly in the Martian atmosphere will not be easy. The 'air' is thin and this will require a lightweight design and large wings to provide lift.

It would be like flying at over 30,500m (100,000 feet) above the Earth. A long-range aircraft flies at about 9,100m (30,000 feet) altitude.

There is also the problem of the eight-minute time delay for radio messages between Earth and Mars.

Space station boost

Elsewhere in NASA's new budget is an extra $2 billion in the next five years to keep the International Space Station (ISS) going and prevent it falling victim to Russia's economic crisis.

In all, President Clinton wants to give NASA $13.57 billion, including $3 billion for space shuttle flights and $2.5 billion for the ISS.

NASA and Russian space officials will meet on 22 February 1999 to discuss the latest space problems caused by Russia's economic crisis.

A 21-ton Russian built service module for the ISS that was to be launched in July has now been put back to September at the earliest. The module will provide crew living quarters and power to manoeuvre the space station.

NASA has made contingency plans to keep the space station running should Russia fail to deliver the service module. It has already purchased an interim control module from the US Navy that should be ready for launch in early 2000 if it is needed.

NASA's budget also includes $75 million for "Triana." Dreamed up last year by Vice President Al Gore, the Triana satellite would be positioned at the point between the Earth and the sun where it would send back a constant image of the entire planet.