It was crewed by astronauts Glyn Williams and Dan Schultz. They were the first to detect the rogue planet Mondas as it came closer to Earth, but their craft was pulled into the rogue planet's gravity. When they tried to break free, the Zeus IV exploded, killing them both. By the time this news reached Space Command headquarters, another probe, Zeus V, had already been launched to help Zeus IV get back to Earth. (TV: The Tenth Planet) The launch of the Zeus IV had previously been profiled on the British news. (PROSE: Mondas Passing)