Early this morning, European Space Agency (ESA) astronaut Luca Parmitano and NASA astronaut Chris Cassidy exited the International Space Station to conduct assembly and maintenance on the spacecraft. The spacewalk was scheduled to last around 6.5 hours and was being streamed live by the space agencies. The mission was cut short, however, by a malfunction in one astronaut's spacesuit.
Shortly into the spacewalk Parmitano reported that there was water floating in his spacesuit helmet, and that the back of his head was wet. NASA's flight director quickly called an end to the spacewalk, and Parmitano and Cassidy made their way back into the space station.
The cancellation made today's spacewalk the second shortest in the history of the International Space Station. Engineers are now searching for the cause of the suspected leak in Parmitano's helmet. NASA has stated that Parmitano was never in any danger and that none of the tasks he and Cassidy were scheduled to complete were urgent or would put the crew of the station in danger. In addition to routine maintenance, the astronauts were rigging cables to prepare for the arrival of a new Russian laboratory module.
The relevant NASA footage of the spacewalk can be seen below. Parmitano can be heard at around the 1:50 mark confirming that the liquid in his helmet is not sweat.