Buzz Aldrin, one of the first two men to walk on the moon, used one of the world's oldest monuments to send a message about the future of space exploration. The 85-year-old former NASA astronaut, who touched down on the moon in 1969 with Neil Armstrong, posted a picture on Twitter of himself in front of England's Stonehenge, wearing a T-shirt reading, 'Get your a** to Mars'. 'While at @EH_Stonehenge yesterday I decided to send a message to the cosmos,' he wrote on Tuesday, accompanying the photo. Stonehenge, a prehistoric ring of standing stones, dates back to between 3,000 and 2,000 BC. Aldrin's picture is the last move in his campaign for the U.S. to focus on having human settlement on Mars. The veteran astronaut has written a series of columns stressing that space exploration should continue. More via Daily Mail Online.