Why send jellyfish to space? Well, because it’s awesome which is true of anything involving space. But mostly because of little crystals that they keep in their bodies, and what these crystals can tell us about long-term human space travel.
When a jellyfish grows, it forms calcium sulfate crystals at the margin of its body (termed a bell). These crystals are surrounded by a little cell pocket, coated in specialised hairs, which are equally spaced around the bell. When jellyfish turn, the crystals roll down with gravity to the bottom of the pocket, moving the cell hairs, which in turn send signals to nerve cells. In this way, jellyfish are able to sense their way up and down. All they need for this to happen is gravity.
Humans have gravity sensing structures too, and therein lies the crux: in space with no gravity, will these structures grow normally? If humans ever want to colonise places in deep space, then we may need to have kids in zero gravity ( via sbs.com.au ).