Over the course of 144 days spent on the International Space Station (encompassing 2,336 orbits of the Earth and covering nearly 62 million miles), Hadfield didn't merely do his day job -- conducting more than 130 scientific experiments testing the effects of microgravity on masses of various types. He also helped to change our concept of what it means to be an astronaut in the first place. Hadfield is a space explorer in the Gagarin/Glenn/Armstrong model, but he is something else, too: just a guy. A guy who happens to be in space. Hadfield, availing himself of new technologies that are just beginning to be widely adopted, made space travel seem accessible. He made it seem normal (or, in astronaut-speak, "nominal"). He took it out of the realm of the awe-inspiring and placed it squarely in the realm of the awesome.

The Right Stuff (for Right Now)

Hadfield wasn't strictly the first to do any of that, of course. He comes from a long line of astro-tweeters, starting with Mike Massimino more than four years ago:

From orbit: Launch was awesome!! I am feeling great, working hard, & enjoying the magnificent views, the adventure of a lifetime has begun! -- Mike Massimino (@Astro_Mike) May 12, 2009

Nor was Hadfield the first to bond with his fellow humans by taking gorgeous photos from space: "The Blue Marble," snapped in 1972 by Apollo 17 astronauts, remains the most iconic image of Earth as seen from beyond its confines. And Don Pettit, a veteran of Expeditions 30 and 31, is still the most prodigious ISS photographer to date, to the extent that he is single-handedly responsible for almost half of all the images taken from the Station. Hadfield also wasn't the first to take advantage of advances in video to show the Earth-bound what it's like to live outside the planet's boundaries: Pettit was a notable YouTuber, and Suni Williams ended her tenure as Commander of Expedition 33 by offering earthlings a fairly epic video tour of the Station. Their work in that regard is simply a tech-afforded continuation of the work done by John Glenn and Neil Armstrong and Buzz Aldrin: Astronauts have long served not just as explorers and scientists, but also as ambassadors. As, essentially, PR people for NASA and for space travel itself. That's a big part of the gig.

Spaceflight finale: To some this may look like a sunset. But it's a new dawn. twitter.com/Cmdr_Hadfield/... -- Chris Hadfield (@Cmdr_Hadfield) May 13, 2013

What Hadfield used to his advantage, though, was the copious combination of social media tools that are just now coming into their prime, tools that transform documentation into conversation: Hadfield had Twitter and Tumblr and Facebook and Reddit, not to mention a public excited, especially after the successful landing the Curiosity rover last year, about space again. Not to mention a 20-person social media team eager to remind the world about Canada's role in the space program. Not to mention a doppelgänger son, Evan, who handled Hadfield's accounts when he couldn't. Not to mention a good deal of luck. (William Shatner's casual tweet to Hadfield back in January won him a flood of followers, Quartz notes, after which his popularity "became self-sustaining.")

Hadfield also had ... Chris Hadfield. He was the right guy at the right time -- and in, wow, the right place: He's a natural performer who seemed truly excited to share his sublime stage with the rest of us. But his performances were intimate rather than epic: He subtly rejected the aura of distant heroism we normally associate with space flyers. Instead, he was nerdy. He was excited. He was delightfully, winkily mustachioed. He was your dad, or your uncle, or your mentor, the kind of guy who probably gets a little choked up when he makes toasts at weddings. Which is to say: He is quirky and real, and he made a point of putting those facts to use. He took all the corporate logic of social media -- the ethos of the "personal brand," the edict of "conversation rather than presentation" -- and applied it, seamlessly, to his life in space.