Re: What would be the effect of Martian gravity on permanent human settlers?

How would Martian gravity effect human settlers?

You ask a many nuanced question here, and I am not sure that I am fully up
to an appropriate response. Gravity on Mars is about 40% that of Earth.
This means that a person who weights 150 lbs on Earth, would weigh only 60
lbs on Mars. So, the average human on Mars might appear as a super athlete
– able to run faster, jump higher, lift and carry larger objects, etc. But,
of course, it’s always more complicated than that.

Part of the problem is that, with current technology, it would take about 2
years to get to Mars. Living for that long in a weightless environment
would have definite effects on the human body. The greatest effect is on
bone density and muscle mass. Bone provides two important functions in the
human body: one is structural support and the other is storage of metabolic
salts. When bones are not tasked to provide structure (as occurs in a the
weightless environment of space) metabolic storage becomes the primary
function. In zero gravity the bones don’t need to contain as much minerals,
and so they are shed and eventually excreted from the body. As a result,
the bones become less dense and more brittle. Similarly, lack of effort
causes the muscles to atrophy. Astronauts on the International Space
Station participate in a great deal of exercise to limit these effects, but
they still cannot avoid them. After a long stay in space they come back to
Earth weakened in both muscle and bone. Because they are generally healthy
people, they tend to recover but it takes a long time. A trip to Mars (two
years in weightlessness) would create these same problems. Living on Mars
would have a similar effect (not as bad, but similar) because of the lower
gravity. When those astronauts return to Earth after living four, or more,
years in low or zero gravity they might face serious health problems in
Earth’s gravity.

You ask about pregnancy and fetal growth in a Martian environment. There is
really no way to answer that question. I am not aware of any experiments
with animal fetal development in space. The problems with fetal development
could go two ways. One way, it could be a serious problem and, since you
can’t get a fetus to exercise, it may be insurmountable. Human fetal
development on Mars could fail. On the other hand, the fetus develops in a
buoyant environment in the womb and therefore its physiology may not be as
effected by lower gravity. It is therefore also possible that the fetus
would develop just fine. Certainly there would be problems with development
after birth. This is the time when a child’s muscles and bones are really
developing their strength to support the body. Without the stresses of
Earth-like gravity I do not think that the child would develop properly. I
cannot predict what the outcome would be, but I suspect that a child who
grew up on Mars, or the Moon for that matter, would have serious health
problems and may not survive to adulthood.