“Stonehenge is being scanned using modern laser technology to search for hidden clues about how and why it was built. All visible faces of the standing and fallen stones, many of which are obscured by lichen, will be surveyed. Some ancient carvings have previously been found on the stones, including a famous Neolithic “dagger”. The survey is already in progress and is expected to finish by the end of March. “The surfaces of the stones of Stonehenge hold fascinating clues to the past,” said English Heritage archaeologist Dave Batchelor. The team will be looking for ancient “rock art”, but also for more modern graffiti, in a comprehensive survey of the site.”

More here – http://www.bbc.co.uk/news/science-environment-12688085 and here –
Video here – http://www.youtube.com/watch?v=qxAnanfB_rg