I basically agree with the conclusions of this article... Humans Will Never Colonize Mars ...and the biggest reason is this... And that’s assuming humans could even reproduce on Mars, which is an open question. Casting aside the deleterious effects of radiation on the developing fetus, there’s the issue of conception to consider in the context of living in a minimal gravity environment. We don’t know how sperm and egg will act on Mars, or how the first critical stages of conception will occur. And most of all, we don’t know how low gravity will affect the mother and fetus. Seidler, an expert in human physiology and kinesiology, said the issue of human gestation on Mars is a troublesome unknown. The developing fetus, she said, is likely to sit higher up in the womb owing to the lower gravity, which will press upon the mother’s diaphragm, making it hard for the mother to breathe. The low gravity may also “confuse” the gestational process, delaying or interfering with critical phases of the fetus’ development, such as the fetus dropping by week 39. On Earth, bones, muscles, the circulatory system, and other aspects of human physiology develop by working against gravity. It’s possible that the human body might adapt to the low-gravity situation on Mars, but we simply don’t know. If we can't colonize Antarctica, we sure can't do it off world.