The CHAPEA experiment simulates the confinement, resource limitations, and interpersonal dynamics of a Mars mission. It cannot replicate crucial physical factors like one-third gravity or high radiation, making it a study of human psychology and group dynamics under stress rather than a physiological test.

The small, non-representative group of initial colonists will create a genetic bottleneck. Their specific genetic makeup will have an outsized influence on all subsequent generations born on Mars, leading to rapid evolutionary change and reduced overall genetic diversity compared to Earth's population.

Isolated on islands with limited resources, species undergo rapid size changes. While Homo floresiensis ('hobbits') and pygmy elephants shrank, other species like Komodo dragons and tortoises became giants. This evolutionary pressure applies to any isolated population, including future human colonists on Mars.

Being confined to environments composed entirely of synthetic materials and sealed windows, with no access to nature, can create a form of psychological distress termed "societal claustrophobia." This highlights a deep-seated human need for connection to the natural world, which, when denied, feels like a form of imprisonment.

The insatiable human thirst for dominance—whether colonizing planets, controlling aging, or possessing a partner—is not just about ego or curiosity. It's rooted in a profound inner void and insecurity. We try to control the external world because we are not whole within.

The first practical step toward making space habitable is developing microbe-based bioreactors. These systems will use local materials on the Moon and Mars to produce essentials like food, medicine, and plastics, creating the self-sustaining ecosystems required for any long-term human presence off-Earth before large-scale terraforming is possible.

Living in a sterile Martian habitat, colonists would only be exposed to a tiny fraction of Earth's microbes. Their immune systems would be unprepared for Earth's vast microbial diversity, making a return journey potentially fatal. This creates a permanent biological quarantine that would accelerate human speciation.

A human born and raised in Mars's one-third gravity would likely not develop the bone density and muscular strength required to withstand Earth's gravity. The physical stress would be painful and potentially debilitating, effectively trapping them on their home planet for life.

Since Mars cooled and had water before Earth, Avi Loeb argues life likely started there first. This primordial life could have been transported to Earth inside rocks ejected by asteroid impacts. This makes humans descendants of Martian microbes and Elon Musk's mission a 'return to our childhood home'.