When the ESA's humble spacecraft Philae touched down on the surface of a comet it became clear that history had been made.
Naturally where there's a life-changing event there's a hashtag, in this case it was #WeCanLandOnACometButWeCant.
Ranging from the outright comic to the ponderous and thoughtful the human race embraced the moment and started listing all the problems (serious and not-so-serious) that the human race is currently facing.
Here are the best so far: