More: Seven things that don’t make sense about gravity
Plants certainly do. Charles Darwin was the first western scientist to show that rooted plants have gravity sensors: plumb lines, effectively, that give them a sense of up or down. Turn a plant pot on its side and you’ll find that the roots continue to grow towards the centre of the Earth.
Grown in space, plants show disoriented roots that don’t get the best access to nutrients and water. Poor starch production is one of a number of adverse effects of this. Some seeds grown in microgravity even produce plants in which the genes are expressed differently from normal.
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Animals suffer a raft of problems if they are deprived of gravity – though we don’t yet know the whole story. “We’ve had animal life in space for half a century, but we’ve yet to have a single mammal go through its life cycle,” says biologist , Nova Scotia, Canada.
We do know that there can be problems from the start. Experiments on the Russian space station Mir found that fewer quail eggs than normal hatched, and chicks from those that did hatch were unusually likely to suffer abnormalities.
Then there was an experiment on the US space shuttle Discovery, paid for by the KFC fast food corporation, that investigated the development of quail embryos. None of its 16 embryos hatched. In normal gravity, the yolk lies next to the shell, but in microgravity it floats in the middle of the albumen. This led to problems in the transfer of gas between the embryo and the shell, which proved fatal for the embryos. Wasser reckons these difficulties could be solved with suitable engineering, or by taking the embryos into space at a later stage.
Even bigger problems emerge if embryos survive to see the light of day. Chicks hatched in microgravity can’t balance and orient themselves well enough to feed. Amphibians have problems with breathing: their instinct is to go “up” for air, but there is no up.
Humans have problems with breathing for a different reason. In space, astronauts’ lung capacity is reduced because there is no gravity to pull the diaphragm downwards. To make matters worse, the liver sits higher in microgravity, further reducing lung size. For a short trip this isn’t too much of a problem, but what would happen to babies born in space?
“We don’t know what happens if you grow from a crawling baby to an adult with smaller lungs,” Wassersug says. “There’s every reason to believe serious problems will start to set in during youthful growth.” It’s the simple things that get you: you can’t cough your lungs clear, for example. This and other seemingly minor complications “could be seriously dangerous by the time you get to sexual maturity”, Wassersug says.
Then there’s the issue of bone loss. To grow properly, our bones need to be stressed by out body’s weight. Space station crews returning to Earth show that we also suffer severe muscle loss in microgravity – possibly enough to make it impossible for women to give birth naturally in space.
Who knows what else could affect us after long years in space? “It’s hard to appreciate how little we’ve learned about development and growth in weightlessness,” Wassersug says.