Astronaut Michael Foale has answered your questions on space.
The British-born space traveller has gone into space and back six times and holds the US record for time spent in space.
He's notched up over 374 days in orbit and walked in space for a total of 22 hours.
We put your questions to him - here are the best ones we received.
Jennifer, 14, Essex: What was it like seeing Earth from space?
Michael Foale: It's an emotional thing when you see the Earth for the first time from space.
You're aware of all the people that you love and of all the things that you value. Just the colours, the brightness, and the impression of the Earth - it's extraordinary.
I saw a huge big black spot over Iraq during my most recent mission on the space station - it was from a broken pipeline near Basra and the plume was going all the way to Baghdad.
I called down and I asked if there was any stories about it and there was only a small footnote in one newspaper that this had happened.
From space, it was a dramatic, huge event that was marking the planet. So these things have different scales and it depends on where you see them from.
Sarah, 13, Manchester: Would you like to go to Mars?
Michael Foale: I would love to go to Mars. I'd like to do it properly prepared. I'd like to know that we had thought about what we're going to do there, how long we'd stay there.
There are a number of very good ways of going to Mars but they need to be discussed at length to see what's the most efficient one.
Today I would say we should go to Mars, land for a year and live on Mars, use rovers, explore, have a base, rather like in Antarctica.
I think the focus on Mars has actually been shaped by the fact that it appears to be the closest environment in which we could live to that of the Earth.
Venus has a nice name. Venus is a planet of about the same size as the Earth, but it is too hot. We know things that say we don't want to go there until we are much, much more sophisticated.
Sasha, 13, London: There have been a lot of questions about man going back to the Moon. Do you think it will happen?
Michael Foale: Yes, I think we should go back to the Moon. I do believe it will happen in about 20 years or less.
I think it depends a little bit on the next US election and the ones after that. It depends on the will of people - the political will. However, it will take place.
The first base on the Moon will be specifically to do research there, learn about being slightly - not completely - but slightly self-sufficient, so that we will be prepared to be able to go to Mars and do the same thing there.
The base wouldn't be a place where you send people to live and not come back from. It would be an outpost where research is done and preparation is made to increase your population.
Jonathan, 13, Tewkesbury: What's the thing you worry most about going into space?
Michael Foale: Well it's making a mistake or disappointing people. It is performance anxiety - it is the same as an actor on a stage.
You don't really think about not coming back - that's not something you should think about, it would just put you in depression, make you nervous, panic and you'll be very ineffective in your job.
I don't want to have any falling out with my crew members.
Jay, 13, Sydney, Australia: How do you go to the toilet in space?
Michael Foale:: Well unfortunately there's a certain amount of detail I can't go into. But the principle is the toilet actually looks pretty much like one you would find on the street in one of those little square boxes - portaloos
But because of the weightlessness, droplets, fluids don't go anywhere - they just float and will disperse as if from a shower. So we need airflows to pull through a big hose with a funnel on it and that collects the urine. We also use airflow to collect everything else into a can.
Sian, 13, Northern Ireland: Has it always been your dream to become an astronaut?
Michael Foale: At the time of the Moon Landings in 1969, I was actually in Torquay on a school break on a weekend, I think it was, with my grandparents down in Devon and I remember it extraordinarily well - it had a profound effect on me.
I was already interested in space flight. I'd had become aware of John Glenn's flights and the X-15 flights in America. But this really fired up my attention. It was just one of those really important moments in my life. I remember looking at those images and thinking, is that really on the Moon?
Kenna, 14, Phillippines What sort of food do you eat in space? Can kids like me travel in space?
Michael Foale:: Well, my favourite food in space is chocolate and I took a lot of extra chocolate because I like it so much. Actually the other most favourite food is a form of nuts and cheese that the Russians make, beyond that it is meat and potatoes - pretty regular stuff with vegetables mashed in and I enjoy those too.
I think you will have a chance to fly in space if you want to do it. I think actually it will be with a commercial company - SpaceShipOne, SpaceShipTwo. And by the time you've earned money for the ticket, SpaceShipTen, you will be able to buy tickets probably to orbit.
Sarah, 13, Cardiff: Do you believe in extra terrestrial life?
Michael Foale: Yes, yes, absolutely.
With all the planetary systems that are being discovered by the Hubble Space Telescope and other telescopes now around the world, the chance of there not being life on other planets seems very small.