Anexcursion outside the International Space Station was called off Tuesdaybecause of a water leak in one astronaut's helmet.

 

An estimated half liter of water or more built up in the helmet of European Space Agency astronaut Luca Parmitano as he and U.S. astronaut Chris Cassidy started their second spacewalk in seven days.

 

NASA mission commentator Dan Huot said neither of the astronauts is in danger. Both are heading back to the U.S. Quest airlock.

The source of the water leak was not immediately known. The astronauts guessed the leak must have come from Parmitano's drinking-water bag.