In last month's post, I began the year with an optimistic outlook for human spaceflight. This month, I plan to bring a dose of realism with an issue that few space agencies or advocates for Martian settlements are eager to discuss. I'm talking about gravity. Or more precisely, its absence.
We have known for many years now that a lack of gravity profoundly impacts our long-term survival in space. At the core of the issue is human physiology. Hundreds of millions of years of evolution have intricately adapted our land-based bodies to Earth's gravitational pull. In low-gravity environments such as those found on the International Space Station, our bones and muscles weaken due to the lack of resistance. Astronauts who spend extended periods in space face significant muscle atrophy and bone density loss, even with rigorous exercise regimens. These changes not only compromise physical strength but also increase the risk of fractures and long-term skeletal issues.
Beyond the musculoskeletal system, low gravity impacts various bodily functions. Fluid distribution is profoundly affected, leading to increased intracranial pressure and vision problems. A paper published last year addresses this concern: the optical properties of the eyes of 13 astronauts who spent 157 to 186 days on the International Space Station were examined, both before and after their missions. The paper's conclusion is clear: micro-gravity induces changes in eye mechanics such as the decrease in scleral stiffness and ocular pressure, contributing to a pathophysiology known as Spaceflight-Associated Neuro-ocular Syndrome (SANS). In other words, if you get the incredible opportunity to live on a space station, you'll find that your ability to enjoy the views will decrease as the years go by. But, more problems abound. The heart, accustomed to working against gravity to pump blood, becomes less efficient, and the overall cardiovascular system is strained. Furthermore, the absence of gravity can disrupt sleep patterns and exacerbate radiation exposure, both of which are critical to long-term health.
Low gravity also impacts our most fundamental necessity if we are to consider permanent space settlement: the ability to reproduce. Past studies using rodents sent to space have highlighted complications in mammalian reproduction and embryo development. And I'm not going to delve into how gravity affects basic human pleasure during a couple's most intimate moments (couples on Mars will manage fine, those on space stations will have to be creative). The harsh reality is that our bodies need the constant pull of Earth-like gravity to maintain health and function.
Space habitats, no matter how advanced, must address these physiological challenges. Solutions such as simulating gravity through rotating habitats have been proposed, yet they come with their own set of technical and logistical hurdles. The creation and maintenance of such environments require vast amounts of energy and resources, raising questions about their feasibility and sustainability. A settlement on Mars, which is about 38% of Earth's gravity, should be less punishing for the human body, although, such effects are truly unknown.
With such uncertainties about the ability of our bodies to adapt to low gravity, it is tempting to think that we might never escape Earth. There might be another way though. With the continued advances in biotechnology and human medicine, we might be able to modify our bodies through gene therapy and robotic technology. For instance, gene therapy could be used to strengthen bone density and muscle mass, counteracting the detrimental effects of prolonged weightlessness. Additionally, nanorobots could be deployed to counteract SANS in real-time, ensuring an optimal vision. While these ideas might seem to belong to science fiction, note that gene therapy is already treating diseases ranging from neuromuscular disorders to cancer to blindness.
As the dream of space colonization continues to motivate us, we will discover new methods to adapt to space. This could imply having an altered body supported by a robotic framework. If we are to live in space, mutants and cyborgs might be the way to go. This is why I placed the 'We' in the title of this article within apostrophes, as I believe that future colonists will not resemble the likes of you and me, but will be 'adapted.' We're building the infrastructure to make space travel more accessible to all, now we need to focus our attention on building a human body adapted for space. Who wants to be the first Homo sapiens astralis?
Upwards and onwards.
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