More than 60 artworks and artifacts at some of Berlin's best-known museums were smeared with an oily liquid by an unknown perpetrator or perpetrators earlier this month, authorities said Wednesday. They were hopeful that the apparently random damage can be repaired, but said the motive was a mystery. The works at the Museum Island complex, a UNESCO world heritage site in the heart of the German capital that is one of the city's main tourist attractions, were targeted at some point between 10 a.m. and 6 p.m. on Oct. 3.