A return mission to the moon offers the best hope of understanding life on Earth and discovering whether alien life lurks in distant corners of the universe, according to a British scientist. Ian Crawford, a planetary scientist at University College London, will today call for the first crewed missions to our nearest celestial neighbour in more than three decades. Speaking at a meeting of the UK's Astrobiology Society at the University of Kent, Dr Crawford will outline how clues to the existence of life in the solar system and beyond may be locked in rocks and debris that crashed on to the moon and were preserved on the sterile surface.