Hadfield arrived at the station on Dec. 21, 2012, and is currently serving as Flight Engineer for Expedition 34. He will take command of Expedition 35 when the Expedition 34 crew depart the orbiting outpost in March 2013. Hadfield will be the first Canadian to command the station.
In his tweet, Shatner wanted to know if his fellow Canadian was in space, to which the astronaut replied: "Yes, Standard Orbit, Captain. And we're detecting signs of life on the surface."
I get the feeling this social media relationship will only grow over the coming months, so don't be surprised if Hadfield's mission takes on a decidedly Star Trek-like flavor. Let's just hope he doesn't report any Birds of Prey sightings.