Muscles deteriorate in space, including the heart muscle. Because bones and muscles must be exercised even more in space than on Earth to keep them in tip-top shape, NASA is beginning a comprehensive study called Integrated Cardiovascular that hopes to find out more about how to counteract impaired heart function, both in space and here on Earth.
A Caltech paper has stated that we can live on Earth for another 2.3 billion years, over double the current estimate. Because of this new hypothesis (if proven true) it should also mean that we have over twice the chance of finding intelligent life out there in the universe.
According to computer simulations by astronomers at the Paris Observatory, in the worst-case scenario, one of the inner planets, either Mercury, Venus, or Mars, could collide with Earth in just over three billion years.