 Officials said the mysterious ooze was actually water with a green dye that came from the building's air conditioning system and was not hazardous. In a statement, they said that green dye is used to easily discover a leak and trace it back to its source. Stacey Lynn, CBS News. Four NASA volunteers are ending more than a year in self-imposed captivity as part of a project they hope will help get astronauts to Mars. They've simulated a Mars mission complete with technical trouble, communications delays.