Sex, the final frontier: Nasa acts to ensure that astronauts don't follow their urges

In the First World War, frontline troops who were away from their loved ones for long periods famously had bromide put into their tea to reduce the distraction of their sexual drive. But yesterday it was suggested that such measures might be taken a lot further - to Mars, in fact.

Dr Rachel Armstrong, speaking yesterday at a British Interplanetary Society symposium on the Human Future and Space, said the US space agency Nasa was considering how to deal with the natural urges of astronauts travelling on long journeys such as a three-year trip to Mars, where the six-strong crew would be likely to include two women.

"Nasa is talking about the chemical sterilisation of astronauts on longer journeys," Dr Armstrong said, in a talk discussing the problems humanity may face in trying to reach the planets and, eventually, the stars.

Nasa was nonplussed by the suggestion yesterday. "I haven't heard anything about that," said a spokesman at Nasa's Johnson Space Centre, where the long-range trips announced by President George Bush in January are being planned.

But that denial may hide a reluctance, in a nation where the showing of a nipple on national television provokes a religious outcry, to discuss the rather delicate subject of sex in space. Certainly, some scientists believe it is a topic that should be dealt with head on. Douglas Powell, a psychology professor at Harvard University who was recruited in 1999 by Nasa to investigate the behavioural needs of long-term space trips, said: "Like anywhere, these are normal healthy people in their prime and they are sexually active so they are going to get involved with each other. So what's going to happen in space? It's a serious question and it needs to be confronted."

Unusually for a space issue, it is one where physical problems would not arise, as the presence or absence of gravity doesn't affect body mechanics.

But scientists such as Professor Powell are concerned that the emotional fallout from having a crew where some are happier than others, or where relationships are made and then fall apart, could be disastrous. He noted the comments of one Russian cosmonaut about time spent cooped up in the Mir space station that "when you have two people locked up in a very small environment for months at a time, all the conditions for murder are met." Mix in sex, and you almost have the script of Othello in space.

Other scientists have suggested that the best way to ensure there is no interplanetary interplay is to crew the mission with astronauts over the age of 50. "The idea is that they won't be worried about having families and concerned about getting exposed to radiation, because they're getting towards the end of their useful working lives," explained Peter Bond, a British expert on space matters.

"Alongside that is the idea that the ideal Mars mission would have - in Star Trek terms - two Mr Scotts and two Mr Spocks, and definitely no Captain Kirks, or Mr Sulus, or Dr McCoys. You need the Scotts to do the engineering stuff, and the Spocks to do the science. You don't need a Kirk because all he does is issue orders - and kiss any woman in sight."

Extraterrestrial entanglement is a topic that has been surrounded by rumour for years. In 2000, a French author, Pierre Kohler, claimed that a "confidential Nasa report" in 1996 showed that two astronauts had joined the 200-mile-high club at the agency's behest as part of tests to see how long humans could survive in space.

Nasa angrily denied the claim, pointing out that the text claiming to be the report was an internet posting containing grammatical and factual errors. Similarly, there were allegations that Russia claimed a space first in 1982 when Svetlana Savitskaya shared the Salyut 7 space station with two Russian male colleagues. Online postings say there were "experiments" to try to conceive the first space child. But there is no independent confirmation of this; instead Savitskaya, who was the second woman in space, and the first to carry out a space walk, says in her memoirs that the two male cosmonauts "welcomed me at the hatch with an apron". She threw it aside and "established a working relationship".

But the push towards Mars raises more difficult questions that Nasa will have to deal with - even though it has always preferred to push sex as far down the agenda as humanly possible.

Interestingly, there is no Nasa ban on sex between crew members. "We depend and rely on the professionalism and good judgement of our astronauts," said a Nasa spokesman in 2000. "There is nothing specifically or formally written down."

And that may be part of the problem. A crew heading to Mars would potentially be away for three years: six months travelling out, two years on the Red Planet waiting for the Earth to come back into alignment for the six-month trip back.

The psychological strains of such a trip would be huge, noted Dr Joanna Wood of Nasa's National Space Biomedical Research Institute, who compares it with the isolation experienced by scientists in Antarctica. But they have the comparative luxury that they can be rescued if necessary. With a Mars trip, there comes a point of no return determined by fuel and the planets' positions.

"Interpersonal relations is a big issue, but we leave sexual stuff to the discretion of the individuals," said Dr Wood.