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