IN 1972, Apollo 17 returned to the US with 50 moon rocks, one for each state. Late last month, Arkansas finally found its rock, which had been missing since 1980. It turned up in a box of Bill Clinton’s papers dating back to his days as governor of Arkansas. An archivist (档案保管员) found the rock in one of 2,000 or so boxes at the Butler Center for Arkansas Studies when he was going through them.