LONDON — Mike Cahill’s “Another Earth” will open Blighty’s Raindance Film Festival, which unspools Sept. 28.The indie sci-fi drama, which world preemed at Sundance, toplines newcomer Brit Marling and “Lost” thesp William Mapother, and follows the crossing paths of two strangers on the night that a duplicate planet Earth is discovered in the solar system. Fox Searchlight nabbed the pic for all English-speaking territories at Sundance and is planning a U.K. December release. Raindance’s full lineup will be unveiled on Sept. 6, and will include more than 80 U.K. premieres, including 30 international features from 25 different countries. The program will emphasize extreme filmmaking, from psychological thrillers, road movies and black comedies, to erotic films and cutting-edge docs and shorts. The fest runs Sept. 28-Oct. 9 at London’s Apollo Cinema.