WASHINGTON (Reuters) - New high-resolution pictures taken by an orbiting NASA camera show clear evidence of man's lunar explorations nearly 40 years after the last U.S. spaceflight touched down on the moon, the agency said on Tuesday. The National Aeronautics and Space Administration released three pictures on Tuesday snapped over the past month by its two-year-old Lunar Reconnaissance Vehicle. The pictures provide the sharpest images yet of the Apollo 12, 14 and 17 landing sites and include a photo of the boot tracks left behind in 1972 by the last U.S.