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Unplanned Spacewalk a 'Precedent-Setting' Move for Space Station Crew

NASA astronauts Chris Cassidy and Tom Marshburn don their NASA-issue Extravehicular Mobility Units for an emergency spacewalk to find an ammonia link outside the International Space Station. Canadian astronaut Chris Hadfield (center) and Russia

Spacewalk to repair ISS

Repairs to the International Space Station began on Saturday morning as

members of the crew suit up and head outside to track down the source of

the ammonia leak discovered on May 9.