Michael Kinser from the United States wants to know how astronauts are preparing to deal with long periods in weightlessness, and high radiation, on journeys to places like Mars. We put the question to ESA's Italian astronaut Paolo Nespoli.
"Well that's a good question. All these problems, radiation - we could build a shield, we could build an electromagnetic shield, we could use water to shield. There are some proposals, some better, some less better," says Nespoli.
However, those two technical challenges are not the biggest worry he has.
"I think the important part is isolation and confinement," confides Nespoli. "I was on Station and I was thinking 'I'm here, and if there is problem, I can jump on my Soyuz, my capsule attached here, and in four hours I will be on the ground. What about if I'm on Mars? What are you going to do?"
Nespoli, who recently returned from his third mission to the International Space Station, said such psychological issues need to be dealt with.
"This starts working in your brain even before you have a problem. So all of this, we need to understand all of this and prepare, and this is what we are doing on the Space Station."
However, the 60-year-old spaceman is still game for a trip to the red planet. "I'm pretty sure we will understand all this, and we will go to Mars," he says, adding with a smile "And I will sign up if I can, please, sign me up!"