The Bonner Ball Neutron Detector is a science payload aboard the International Space Station that measures neutron radiation. Neutrons are uncharged atomic particles that have the ability to penetrate living tissues. Neutron radiation can affect the blood-forming marrow in the mineral bones of human beings and other animals. By operating the Bonner Ball in space, neutron radiation information can be collected and used for the development of safety measures to protect crewmembers during long-duration space flights. The Bonner Ball arrived on the station during STS-102 and will return to Earth on STS-108.