The immune system fails because of a cascade effect. Our adaptive immune system (antibodies) depends on activation signals from the innate system. Because the innate system's receptors can't bind to mirror molecules, the initial alarm is never sounded, preventing the entire defensive chain of command from launching.

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.

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.

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.

Mirror life's molecules are mirror images of normal biology. Our immune receptors, like right-handed gloves, cannot properly bind to these 'left-handed' pathogens. This fundamental shape mismatch, not just novelty, prevents an effective immune response, making it a uniquely dangerous threat.

To shield against radiation and meteorites, Martian habitats will likely be built underground, not in glass domes. A society that lives its entire existence underground, reliant on artificial light and disconnected from an open sky, would develop a psychology profoundly different from Earth's.

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'.

Women raised in one-third gravity may have bones too brittle for natural childbirth, risking fatal pelvic fractures. If C-sections become the norm, the evolutionary pressure that limits a baby's head size to fit the birth canal is removed. This could lead to the rapid evolution of larger-headed humans.