Thanks for all the brilliant questions, I've really enjoyed answering them and sorry to those of you who didn't get an answer. There are loads more answers in my new book Ask An Astronaut and proceeds go to the Prince's Trust.

The selection process took a year and covered many different areas. Some of these are these that you simply cannot train for such as your medical condition and psychology. However, some areas such as communication skills and teamwork are things that you can practice and get better at throughout your career. I found the hardest part of selection were all the tests we had to do on the very first day. This covered areas such as maths, science, language, concentration, memory, spatial awareness and it was a very stressful day. At the time I had no idea how well I had done, but when I was told I'd passed I knew that for me that was the most difficult hurdle out of the way.

That's a great question. Actually the pressure inside the Soyuz spacecraft doesn't change rapidly during the entire flight. It slowly decreases as we breathe but then our atmosphere is replenished. So our ears do not pop during launch or during the ride into space. However, when we do a spacewalk we have to decrease the pressure in our spacesuits more rapidly, which can cause your ears to pop, and for this we have a device inside our helmets where we can use our nose to help equalise the pressure in our ears.

The good news is that ESA is not part of the EU. This means that the UK will remain one of the most important members of the ESA. The UK is a world leader in areas such as telecommunications, small satellite technology and robotics and we will continue to contribute to many important ESA space exploration programmes beyond Brexit, including astronaut flights.

What's truly impressive about earth during the daytime is the vast scale of geological features. For example, mountain ranges such as the Andes, the Himalayas and the Alps are stretching over hundreds of miles. And also the sand dunes of the Sahara desert - these present a stunning view from space.

I'll just have to pick one of these but thank you for all of them!

21. Ollie - How tiring was it running the marathon on a treadmill in Space?

Running the marathon was very tiring. However, my legs weren't working as hard as they would have been on earth as the harness I was wearing could only generate about 70% of my body weight, keeping me down on the treadmill. But the harness became painful after about an hour as it dug into my shoulders and rubbed on my waist. I decided to speed up as I had to finish the race as quickly as possible. My ground support team thought I was doing well! It was only afterwards that I told them that the reason I ran the marathon quicker than expected was because the harness was hurting so much. Did I hit the wall? After about 18 miles the marathon became much harder. But I was very grateful that mission control were streaming the live London Marathon coverage onto a laptop that I could watch whilst running the race which gave me the huge motivation to finish.

The space station runs to the same time as the UK in winter. Normally after 10pm the space station lights are dimmed and everyone keeps the noise down. You can sleep anytime between 10pm and 6am. However, most astronauts feel they don't need as much sleep in space as they do on earth (maybe that's because we're not working as physically hard in weightlessness and so our body doesn't need as much rest). I usually slept from midnight until 6am.

Leaving the sanctuary of the space station was the most exhilarating moment of my mission. Looking down on planet earth with only a thin visor between me and the vacuum of space gave an incredible perspective of our place in the universe. It's hard to describe that feeling. But it was very powerful and a beautiful sight. It changes your view of planet earth and just how fragile it is. We would do well to look after that thin tiny atmosphere which protects us from the vast blackness of space.

Yes although this will be a gradual process. We have to overcome some obstacles with radiation and propulsion in order to travel to Mars but these are not insurmountable. In terms of travelling further into the Solar System, I think that that will become a reality in the next 100 years or so. In order to achieve such audacious missions we will have to continue to work together in international partnerships between the national space agencies and also partnerships within the commercial space sector.

Towards the end of the mission, we had an unusually clear pass over South America. This was the first time I'd been able to see the Amazon rain forest as a whole and to witness the vast areas of deforestation that are occurring there.

No. In 2009, the average age of the NASA selection was in the low 40s. The European Space Agency average age was mid 30s. Becoming an astronaut is a mixture of having accumulated enough expertise and qualifications in your life and still having enough time to dedicate to the space programme. 45 is probably at the upper limit for being selected.

Yes. In order to cut the transit time to Mars down to a matter of weeks instead of months we need new propulsion technology. This could be in the form of iron thrusters or nuclear propulsion and even matter anti-matter reaction engines could be possible in the future.

I have two small boys and I love building both. If I had to choose it would probably be sandcastles.

We don't tend to get colds in space because of the two week's quarantine prior to flight. However, it's possible to get an infection or to have an injury working on the space station - for this, we are well trained as crew medical officers (we're even trained on how to extract teeth) and there's a pretty good medical cabinet onboard the space station. Of course we also have our flight surgeons who can give us advice on any medical issues. If you did have a cold in space it would just pass like a normal cold.

We don't see borders from space.

Re-entry into the earth's atmosphere is a pretty wild ride. The capsule gradually experiences more and more deceleration. We feel this inside the capsule as a heavy weight on our chest. It becomes harder to breathe above 4Gs and it takes about eight minutes to travel through earth's atmosphere, until the parachute opens. The parachute opening itself is a crazy 20 seconds which is like a wild rollercoaster ride. I didn't feel claustrophobic as by that stage I had already spent six months living in a very confined space station.

Maybe I won't answer this exactly as you would like. But there has been a Japanese experiment where mice that had flown to space were used for breeding on their return to see if any changes caused by microgravity were passed on to their offspring.

Often in the first day or two in space, astronauts will feel sick. But this is not like seasickness which can be debilitating over a long period of time. Space sickness comes over you very quickly and is gone very quickly. It's the body attempting to work out what is going on by all the confusing signals it receives in weightlessness from the eyes and ears. Emptying the stomach is part of that process. I was lucky - this didn't effect me very badly in space. But I felt pretty rotten coming back to earth.

Air flow is our friend in space. The ventilation fans keep all bad smells moving into the filtration units. This is not just to carry away bad smells but it's also important to prevent pockets of CO2 building up so that we have enough fresh air to breathe.

A future mission to Mars would be an incredible experience. At the moment I have two young boys and a duty as a father and husband, so being away for three years right now would not be an ideal situation (I think my wife would agree with that too). But in the future I would definitely consider a trip to Mars.

How do I juggle family life and space travel? Training as an astronaut involves an awful lot of time away from the family so it's difficult but very important to try and find a balance between work and home life. I do this by making sure when I'm not travelling I'm as involved as I can be as a father and husband.

The ISS actually smells quite clinical and metallic. Space itself has a smell of burnt metal and ozone. But after a while in space, your sense of smell deteriorates. You often get stuffy nosed with the increase of pressure in your head (caused by body fluid shifting up into the chest).

You might joke, but the Russian segment runs on 28v and the US segment runs on 110v, so yes we did need adaptors!

Yes. In space I actually had to work hard to keep the calories on. So I was able to eat really nice puddings every evening, such as chocolate pudding cake, lemon curd cake, key lime pie ... I miss all of that. I don't have time for dessert these days.

Hello, Tim Peake here. Really looking forward to answering your questions on anything to do with space, life, the universe. Bring it on!