Mir's commander Viktor Afanasyev and French flight engineer Jean-Pierre Haignere were expected to spend five hours in space. But they only re-entered Mir after six hours 19 minutes, with some work not completed.

A previous Mir space walk, 390km above the Earth

The trouble began when extra time had to be spent fixing a problem with the spacesuit ventilation system of one of the cosmonauts.

Haignere was "a bit hot" at the time. "But I'm not paying any attention to it," he said during a radio link-up with Earth. "I'm too busy."

Next, a test of a hole-repair kit had to be abandoned when a container of glue failed to open in space. Vera Medvedkova, a spokeswoman for Mission Control, said the reason was a faulty valve.

Because they were behind schedule, the cosmonauts had no time to set up a device called Octopus to test radiation levels around Mir.

Other tasks were successfully completed. Afanasyev and Haignere attached cases of living matter to the outside of Mir. This experiment may reveal if alien living material could survive a journey through space and "seed" life on Earth.

The Mir space station has seven modules

The cosmonauts placed more than 30 organic samples outside the station. They are covered with a material similar to a stone meteorite, to simulate the host rock of any material that might have been delivered to Earth.

They also retrieved a French "meteorite trap", installed earlier this year to catch microscopic cosmic debris from a passing meteor storm.

In the final part of the space walk, a small satellite made by Russian and French schoolchildren was put into space. If it works, the satellite will beam a recording of their voices that will be heard on Mir and at Mission Control, near Moscow.

Mir's current three-man crew may be its last. If outside investors cannot be found to foot the 13-year-old station's $250m yearly costs, the cash-strapped government may have to discard the station in August.