For many, the most surprising moment from the first teaser trailer for Thor: Ragnarok isn't the seeming destruction of Asgard, a rampaging Hulk or even Chris Hemsworth's Thor with short hair - it's watching Mjolnir, Thor's enchanted hammer, literally fall apart. How can Thor manage without his beloved weapon? Turns out, he's had quite a bit of practice in comic book lore.
Unlike the cinematic Thor, the comic book Thor's relationship to Mjolnir has been significantly more complicated at points throughout his career. For the first two decades of the comic series, Thor couldn't be physically separated from his hammer for more than 60 seconds without transforming back into his human guise, Dr. Donald Blake. That enchantment was undone in 1984's The Mighty Thor No. 340 - in the process, essentially "killing" the Donald Blake persona - but a version briefly reemerged five years later, when Thor No. 408 split the hero's life-force between himself and regular guy Eric Masterson, an arrangement that would last until 1993's Thor No. 459.
(A third human identity/disguise, Jake Olson, lasted from 1988's Thor Vol. 2 No. 1 through 2000's Thor Annual 2000, and again, separation from the hammer would force Thor to become human during this period.)
In 2014's Original Sin No. 8, Thor surrendered the hammer after becoming unworthy to hold it (the enchanted hammer, for those who don't remember, can be lifted only by those worthy enough to handle the power of Thor, as per Odin's bidding). That had the unexpected result of creating two Thors in current Marvel comic book continuity: the original, whose name is Thor and who attempts to redeem himself, and a replacement - Jane Foster, his former girlfriend - who is able to wield the hammer, and so has taken on the power and title of Thor in the original's absence.
Beyond that, Thor has dealt with the seeming destruction of Mjolnir more than once - and each time, it's always come back together when most necessary. (Bad news for Cate Blanchett's Hela, although the larger Marvel Cinematic Universe might be heartened knowing this, nonetheless.)
While 1965's Journey Into Mystery No. 119 showed that the hammer could be damaged - it loses a fragment during a battle, although it's quickly repaired between issues - it wasn't until 1982's Avengers No. 215 that it was actually destroyed for the first time … and even then, at the hands of a villain who had control over the molecular structure of all reality. Upon his surrender, said villain then restored the hammer entirely, because that's just good manners. It was a similarly oversized, cosmic threat that destroyed the hammer the second time around, when 1988's Thor No. 388 saw the hammer destroyed after the hero used it to attack a near-omnipotent alien attempting to destroy an entire planet. Once again, the alien restored the hammer in surrender.
1999's Thor Vol. 2 No. 10 saw Mjolnir cut in half by the Dark God Perrikus, in a particularly dramatic scene -
- but this would prove to be a short-lived change to the status quo. The following month's Thor No. 11 repaired the hammer in a novel, if ridiculous manner: Simply by touching it, Thor managed to fix it because … the plot demanded it. (A similarly brief breakage would occur in 2009's Thor No. 600, where the hammer is destroyed by a deposed former ruler of Asgard; it would be fixed the next issue by Doctor Strange.)
The most long-lived loss of Mjolnir comes, curiously enough, from a comic book story that shares its name with the new movie. The first chapter of "Ragnarok," in 2004's Thor No. 80 - saw the hammer destroyed during a confrontation in which it's attacked by other enchanted weapons, and it wouldn't reappear until 2006's Fantastic Four No. 536. In the meantime, Thor himself had apparently died, and Asgard was seemingly destroyed. Such was not the case, of course, but for all intents and purposes, the Thor mythology was over; the reappearance of the hammer presaged the reappearance of Thor himself the following year.
The lesson, then, might be that it's relatively easy to fix a broken magic hammer - especially if Thor can do so just by holding it - but that any fixes should be done quickly, or else Thor and his entire race will apparently die. Perhaps a lesson to bear in mind going into Thor: Ragnarok this November … and maybe a sign that Marvel's Thunder God might want to start carrying around the mystical equivalent of superglue wherever he goes, just in case.