In this handout image provided by the European Space Agency (ESA) and NASA, the International Space Station and the docked space shuttle Endeavour orbit Earth during Endeavour's final sortie on May 23, 2011 in Space. Italian astronaut Paolo Nespoli captured the first-ever images of an orbiter docked to the International Space Station from the viewpoint of a departing vessel as he returned to Earth in a Soyuz capsule. (Photo by Paolo Nespoli - ESA/NASA via Getty Images)
One of the cooling systems on the International Space Station has been shut shut down because of temperature fluctuations, cutting the artificial satellite's cooling ability in half.
Shutting down the modules -- Kibo, Columbus and Harmony -- means that the six astronauts will have to stay in the other modules for now, NASA said.
Officials don't know yet whether the problem resulted from a software glitch or involves hardware, so it's unclear whether a space walk will be needed to resolve the issue.