In July 1969, the world watched as two men set foot on the Moon. For the first time, humanity had ventured out of the planet and touched the possibility of worlds beyond. But our space travel ambitions seem to have stalled since the 1970s and 1980s. In over 30 years, we've ventured virtually no further than the original pioneers. And as more astronauts have spent more time aboard the various space stations, they have reported worrying health problems. As recent tragic events have shown, the most dangerous part of any space journey is taking off. Trying to reach the speeds needed to escape Earth's gravity is fraught with peril. But even once they reach space, astronauts are not out of danger. Instead, they are exposed to a new set of risks which we are only just beginning to understand. Astronaut Chris Hadfield spent months living in space aboard the International Space Station. According to Hadfield, zero gravity changed his body and how he lived with the constant threat of high-speed micrometeorites. We were made to live on Earth, not in the extreme conditions we find in space. So when astronauts like Chris Hadfield leave our planet, they have to take their environment with them. That’s why they wear specially-designed spacesuits. But spacesuits do much more than just keep Earth's atmosphere around astronauts. Over the years, spacesuit design has evolved to protect humans from the harshness of space. In Earth's orbit, astronauts might experience temperatures as low as -129°C (-200°F) and as high as 121°C (250°F). Spacesuits have been cleverly designed to protect us from these extreme conditions. They also provide air pressure to prevent our bodily fluids from boiling in the hard vacuum of space. But astronauts can only travel so far in the spacesuits that exist today. Even our best suits are limited to a ‘low-Earth orbit’. To push farther into the Solar System, we will need a new suit – one that will shield us from the lethal hazards of deep space. But even then, are we sturdy enough to survive a long mission? A spacesuit may protect us externally, but space can have devastating effects on the internal workings of the human body. On Earth, we have evolved to work in harness with gravity. Our muscles and bones have developed to expect this force and it is needed to keep them strong and healthy. In space, astronauts float weightlessly. This looks like a lot of fun, but prolonged exposure to a microgravity environment can have insidious effects on the human body. Space travel plays havoc with our blood circulation. Human cardiovascular systems are designed to pump blood steadily around the body against the force of gravity, which normally pulls blood towards our feet. But in the microgravity of space, blood moves up to the chest and head, giving astronauts puffy faces and raised blood pressure. Muscles are also threatened by space travel. Without the need to work against gravity, muscles can start to waste, which increases the risk of tendonitis and fat accumulation. The lack of gravity even makes astronauts stand up to two inches taller, as back vertebrae separate without the compression of gravity, leading to painful back-aches. Over the long term, astronauts suffer the devastating consequences of bone loss. Microgravity causes the body to lose calcium and phosphorus, leading to a gradual weakening of bone and an increased risk of osteoporosis. Bone loss can be as high as 1.5% of its mass per month, which is roughly 10% over a six-month stay in space, with the recovery after returning to Earth taking at least three to four years. In an attempt to combat this, astronauts living on the International Space Station must carry out 2.5 hours of exercise a day, six times a week.