After the return of a crewed planetary space mission, the removal of harmful substances from an astronaut, spacecraft, and any samples collected. When the Apollo 11 crew returned from the first landing on the Moon, many scientists believed lunar micro-organisms might infect the Earth. In preparation, the US government formed an Interagency Committee on Back Contamination, and NASA built its Lunar Receiving Laboratory to quarantine the crew and lunar rocks until the 21st day after the Moon landing.