Wanted: one organist for concert in remote Bolivian jungle accessible only by raft. Must be prepared to face rapids, alligators and 30C (86F) temperatures. Ability to swim a bonus. Church organists are rarely an essential part of expeditions into the Amazonian rainforest, but a team of scientists about to embark on a journey to a far-flung meteorite impact site in Bolivia believe that one will be key to achieving their mission.