Astronaut Scott Kelly at one point in his life, held the record for the most consecutive days spent aboard the International Space Station, an achievement that unfortunately has come with a high cost. Upon returning home to Earth, Kelly now suffers numerous health problems caused by living in space, but he expected as much when he signed up for his 340-day mission. Scientists studying the effects of outer space on the human body hope that Kelly's readjustment to Earth will help them better understand how living sans gravity affects a person's health. Kelly, who has an identical twin brother who also happens to be an astronaut, makes for a perfect subject when examining space-related health issues. Both he and his brother, who spent six months in space, could shed light on the short and long-term health problems caused by outer space.

After spending a year back on Earth, Kelly now shares his health struggles in a new book entitled Endurance. While his experiences may sound like something out of a TV show about space, Kelly's medical issues are tragically real. Scott Kelly's health problems sound absolutely grueling, and he will face issues with his health for the rest of his life. Space already sounds scary enough, and the effects of space on Scott Kelly's body show living in zero gravity comes with zero health perks. Check out these excerpts from Endurance that won't exactly have you signing up for that first trip to Mars: