From the discovery of a major leak in the International Space Station's coolant systems just 48 hours ago, two Astronauts - Chris Cassidy and Tom Marshburn are currently outside the Station doing a 6.5 hour Spacewalk, the 168th in Space Station history, to try find and repair the leak in the system.<br /><br />The coolant system uses ammonia which is fed through cold plates and transfers heat away from many electronic components used to power the Station's systems.
