https://www.theregister.co.uk/2018/05/24/comet_67ps_cute_rubber_duck_shape_causes_bright_jets_to_shoot_out_every_morning/

Scientists have found that the jets of ice and dust wafting from comet 67P are down to the way sunlight beams hits its unique rubber ducky shaped surface.

In a paper published in Nature, a group of astronomers studied why the sublimation process was concentrated into jets instead of a homogenous cloud of material.