Mars is considered the main candidate for colonization, but its conditions are very different from Earth's. According to Vladislav Nikitin, Candidate of Physical and Mathematical Sciences and Associate Professor at PNRPU, weak gravity and high radiation will gradually change the appearance of humans — after just a few dozen generations.
The main change is height. Due to the fact that gravity on Mars is almost three times lower than on Earth, the spine and joints will experience less pressure, the scientist explained. The intervertebral discs will expand, the bones will lengthen, and as a result, height can reach 210–230 centimeters — like basketball players on Earth.
But with growth will come other changes. Due to the lack of the usual load, bone density will decrease by two to three times. The skeleton will become more fragile and hollow, according to Nikitin.
The heart will also change. It will not have to work with the same load, so it will decrease in volume and beat less often.
Even if conditions on Mars improve — for example, an artificial atmosphere is created — it will not be possible to completely get rid of the problems. There is always a lot of dust on the surface of the planet, and global storms can last for weeks.
Because of this, the scientist suggests, people may develop additional eye protection — a kind of third eyelid in the form of a transparent membrane. The nasal passages will narrow and become covered with thick hairs that will filter dust.
Even the way the respiratory tract is cleared will change: the main reflex will not be coughing, but sneezing — a sharp exhalation through the nose, which is better at dealing with dust.