The Impact of Low Gravity on Human Physiology

Extended stays in space significantly affect human bone density. A study conducted in 2013 revealed that astronauts lost an average of over 10% of their bone density after missions lasting between 120 to 180 days. David Armstrong, an astrophysics professor at the University of Warwick, noted, "Mars has more gravity than the ISS [International Space Station], but it’s still about one-sixth of Earth’s. This raises serious concerns about the feasibility of long-term human life there, especially if you consider raising children."

Armstrong posed a critical question: "If even trained astronauts experience significant bone density loss equivalent to what one would typically lose by age 50 or 60, how could someone live there permanently?"

Microgravity also results in a decrease in muscle mass, and according to Kevin Moffat, an expert in human physiology in extreme environments, there is currently no definitive method to counteract this effect. He remarked on the uncertainty surrounding muscle conditioning exercises performed by astronauts, such as those used by Tim Peake, who ran the London Marathon on the ISS.

Furthermore, Moffat observed that the lack of gravity causes astronauts' hearts to change shape, potentially increasing the risk of kidney stones. He cautioned that this alteration may also impact other bodily functions in ways that remain unknown.

Alterations to Immune Function and Microbiome

Moffat highlighted two other frequently overlooked areas of human physiology affected by space travel: the immune system and the microbiome. He explained that "natural killer cells," which play a role in cancer defense, see a significant drop in astronauts on the ISS. While a six-month stay may not lead to severe consequences, prolonged exposure raises concerns about immune system functionality over years or even a lifetime.

The reasons behind the decline in immune function are still under investigation, but Moffat suspects a connection to changes in bone density. Additionally, astronauts' microbiomes also experience shifts, which could impact their dietary needs.

The Danger of Radiation Exposure

Earth's magnetic field and ozone layer shield us from solar radiation. However, astronauts on the moon or ISS are exposed to higher radiation levels than on Earth, and deeper space missions carry even greater risks. This represents a significant challenge for Bezos' O'Neill cylinders, as the amount of shielding required could reach tens of millions of tons, making it economically unfeasible to transport such materials into space.

Musk's plans for Mars expeditions would require contingencies for sudden radiation bursts from solar activity. Armstrong explained, "In case of heightened solar activity, astronauts might need access to specially shielded areas on their spacecraft."

The Complexities of Terraforming and the Lessons from Biosphere 2

While Musk has expressed interest in terraforming Mars, Armstrong acknowledged the challenges involved. Given Mars' thin atmosphere and weak gravity, many molecules escape into space, making it unlikely that humans could live on the surface without protective domes.

Moreover, the concept of living in domes raises its own set of complications, as demonstrated by the Biosphere 2 project in the 1990s, which faced numerous unforeseen difficulties, including air pollution from deteriorating concrete.

The Toxicity of Martian Soil

The notion of cultivating crops on Mars, popularized by the film "The Martian," faces significant hurdles. Armstrong noted that while experiments suggest some success in growing plants in simulated Martian soil, the actual Martian soil contains harmful substances like perchlorates that could be detrimental to human health.

The Question of Governance in Space Colonies

Aside from the technical and biological hurdles, there are broader social implications of colonizing space. Political philosopher Felix Pinkert suggested that an off-world colony would lack the democratic structures familiar on Earth, as initial missions would likely consist of a small group of experts, potentially creating a hierarchy.

He warned that if private companies control space colonization, it could lead to authoritarian governance. "Companies operate like governments, but they are private entities, governed by shareholders rather than the people they affect."

The Urgency of Space Colonization

Despite the myriad challenges, the experts expressed a belief that space colonization is inevitable. Armstrong remarked, "In small-scale efforts, it might be closer than anticipated. Even if it means sending a few individuals to Mars under harsh conditions, Musk's resources make it a real possibility."

However, he highlighted ethical concerns regarding who would get to leave Earth. "While the colonization may succeed, most of humanity will remain on Earth, which raises difficult ethical questions about the selection process led by a few billionaires."

Moffat took a more fatalistic perspective, asserting, "As a species, we have to pursue this. Our planet is at risk, so we might as well strive for Mars."

The experts unanimously agreed that despite the overwhelming challenges, the pursuit of space colonization should continue. "If the alternative is Elon Musk investing in luxury yachts, this endeavor is undoubtedly preferable," concluded Pinkert.