Long Years, Short Days One day on Mercury (the time it takes Mercury to rotate or spin once in relation to the stars) is equivalent to 59 Earth days. Mercury's day-night cycle lasts 175.97 Earth days. Mercury completes one orbit around the Sun (one year in Mercury time) in just 88 Earth days. It takes Mercury longer than Earth to circle the Sun because it orbits closer to the Sun. Mercury has very little air to breathe, so there is no place on its surface where humans could live. But we know that it used to be covered by ice and snow, and some scientists think that part of it may still be frozen under its crust. Any water that does get released from beneath the planet's crust would be extremely hot - hundreds of degrees Celsius (well over 400 degrees Fahrenheit) - making it unsuitable for life as we know it. But even if Mercury wasn't too hot for human life, it would be impossible to survive there for any length of time. The pressure during most of the year is almost enough to crush a human body into a fine powder. Only when Mercury is close to the Sun do we begin to feel its effects; at those times the pressure reduces slightly. The best place to go on Mercury would have to be one of its two magnetic poles. They are regions of intense magnetic activity caused by dynamo-like processes going on within the planet itself.