Kenneth Bowersox, Donald Pettit and Nikolai Budarin told reporters of their immediate sense of relief at their landing on the plains of Kazakhstan Sunday at the end of the first manned space flight since the Columbia shuttle disaster.

"I had some very keen sensations," Bowersox said, speaking in Russian. "Firstly, when I saw the brown ground and the green grass: it was amazing.

"Secondly, when I saw my wife after arriving here (in Star City), and thirdly, when I walked around Star City and it rained -- a wonderful, chill rain."

His Russian colleague, flight commander Nikolai Budarin, recalled their impressions after emerging from the landing capsule.

"We lay on the ground, breathing in the fresh air which we had missed very much. We were happy ahove all that we made it back to Earth," he told a press conference at the Star City astronaut training centre outside Moscow.

The three men, who spent more than five months in weightlessness aboard the International Space Station (ISS), were only able to crawl on the ground for their first hour and a half of their time back on Earth, he said.

Bowersox recalled the tears they saw in the eyes of their wives when they met up again. Russian rescue services took more than two hours to locate the astronauts after their off-course landing.

The spouses had been "especially worried after what happend with Columbia," the US shuttle that broke up on re-entry on February, causing the death of its seven crew members, he said.

On the issue of whether it had been human error or a mechanical failure that had sent the capsule some hundreds of kilometres (miles) from its intended landing zone, Bowersox was inclined to seek a mechanical explanation, although he could not be categorical.

"You can never say for sure you didn't make a mistake. However we didn't see any sign on board that we made any errors. The important thing is to analyse the situation, find out the truth, and see why the mistake occurred, if there was one, so that it doesn't happen to other people."

Russian space officials said Monday that a cosmonaut pressing the wrong button could have caused the descent capsule to land 440 kilometresmiles) off course in the Kazakh steppe.

"There is a button and it was covered. I double-checked that because that's always the first thing you worry about," maintained Bowersox.

Budarin also denied crew error, saying the landing had been set on automatic mode and they had not "issued any commands that might have led to ballistic entry."

"It's for the specialists to figure out" the cause of the malfuction, he added.

The Soyuz TMA-1, based on technology dating back more than three decades, was forced to land using an uncontrolled ballistic re-entry rather than the usual manual or automatic procedure.

The three men were originally to have left the ISS in March on a US space shuttle but their return was delayed after the Columbia disaster on February 1 caused NASA to ground all shuttle flights.

Russian spacecraft now provide the only transportation to the space station.

Because of the ballistic entry, the crew had a very rough landing, briefly experiencing more than eight times the force of earth's gravity.

Pettit, who still appeared unsteady on his feet, described a crushing feeling of weight during the descent.

"For a moment it felt like I was Atlas and I had the weight of the whole world on my shoulders," he said.

"It takes a while to get your shore legs back after an expedition like this. I've had a little more trouble walking around than others," he noted.

Budarin, a more experienced cosmonaut, said he had already taken a Russian banya (sauna) and jumped into a swimnming-pool and was enjoying doing a NASA exercise of walking between poles to get his body back into shape.

SPACE.WIRE