There are a lot of massive physical challenges that NASA has getting humans to Mars. We need to be able to store enough fuel to get there, arrive fast enough to minimize radiation risk, and we need to be able to land a large vehicle softly on the surface – a vehicle that could be as large as a two-story house.

Then there are the social problems. Whoever was chosen for the Mars mission would need to get along, as it would take around and a year and a half for them to get to the red planet and return, and they'd be in extremely close proximity in their spacecraft. They'd need to get there and back without annoying each other, or turning the whole journey into a horror 

NASA has of course looked into these social problems and sent six scientists to live in a small dome to see how well they cope. 

Now a rumored study by NASA has gone viral for the wrong reasons. The research, which is thought to have been conducted by NASA "some years ago," supposedly concluded that a mission to Mars should be all-female to avoid the astronauts having "impure thoughts" on their way to the planet. I.e. they'll keep their minds on the mission, and won't be distracted by thoughts of sex, or having sex with their fellow astronauts.

At at the New Scientist Live festival in London last Thursday, British astronaut Helen Sharman spoke about the plans. 

"I did hear some years ago that there was a report," she said according to The Independent. "Nasa has never released it, but it was done to see exactly the kind of crew makeup was necessary for the reason we have already alluded to."

"It found that the crew should be the same gender – all men or all women."

The report warned that mixed-sex crews could end up having sex with each other. The plans have gone viral after they were written about by The Independent, with many, many people pointing out some of the obvious flaws in the plan.

The "secret" report, which allegedly came out years ago, also concluded that crews should be all-women due to better co-operation skills.

Other benefits of having an all-female crew include the fact that women generally need fewer calories per day. On a mission where every gram of weight has to be thought about, this is a real advantage.