Long-term survival in space remains a final frontier

It is widely assumed that future space exploration will include lengthy periods of space travel by astronauts and living for months/years in bases on the moon and planets.

But this assumption seriously underestimates the dangers to the human body posed by extraterrestrial environments, not to mention the huge financial cost of funding ventures in space. These various obstacles are considered by Sarah Scoles in Scientific American (October 2023).

Outer space is hostile to human life that evolved on Earth and is attuned to Earthly physical and social conditions. Our muscles waste and bone growth is inhibited in low-gravity conditions. Living in space negatively affects the human microbiome, circadian rhythm and eyesight, weakens the heart and immune system and radiation in space damages cells throughout the body, increasing the risk of cancer and fatal at higher radiation levels.

Radiation refers to various forms of energy emitted as rays and/or particles. Here on Earth we are exposed to various radiations including visible light, ultraviolet light, infrared radiation, X-rays and gamma rays.

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Visible and ultraviolet light reach us from the sun and, taking sensible precautions, are not dangerous. Infrared radiation is perceived as heat, and is easily protected against. We are exposed to X-rays mainly through medicine, for example, chest X-rays. Gamma rays, penetrating like X-rays, reach us from radioactive substances present in rocks, for example, uranium. Under normal circumstances neither medical X-rays nor gamma rays pose significant health hazards.

However, beyond Earth, space is replete with radiations that are all damaging to human health. These radiations are mainly composed of atoms stripped of their electrons and moving at speeds approaching the speed of light. These particles come in three varieties: solar wind particles trapped in Earth’s magnetic field (Van Allen belts); particles shot into space from periodic solar flares, and galactic cosmic rays (GCR) from beyond our solar system.

Earth’s surface is shielded from space radiations by our magnetic field and atmosphere. No such protections apply in space. Water barriers can shield against solar flares but no shielding is fully effective against GCR.

Exposure to high levels of radiation in space is deadly, causing radiation sickness, with nausea and vomiting and death within days or weeks. Chronic exposure to lower levels of radiation increases the risk of cancer. It is easy to appreciate how radiation is such a big problem for astronauts when you consider that, with current technology, it would take six years to travel to Jupiter and 12 years to travel to Neptune.

The potential for radiation to seriously injure astronauts living in space for extended periods is so great that such ventures may not be feasible until research develops methods to allow the body to heal itself from radiation damage.

Even throughout the 1960s Americans didn’t believe Apollo was worth the cost and today only 18 per cent of people believe that sending astronauts to Mars should be a ‘top priority’

One goal for future space colonisation is the creation of self-contained, self-sustaining spaces where humans would live for long periods. This concept can be tested here on Earth, as Scoles explains. For example, in 1991 eight people entered Biosphere 2, a self-contained, self-sustaining space in Arizona, and lived there for two years. Biosphere 2 is a 3.14-acre oasis enclosed in a capsule with different terrestrial environments – ocean, wetlands, tropical rainforest, savannah grassland and desert. However, the experimental results weren’t reassuring. The capsule environment didn’t create enough oxygen, food or water for the inhabitants – this might also happen in a future moon/Martian biosphere.

And then we have psychological ill effects of space travel. Future astronauts will have to handle living in “tin cans” for extended periods, travelling through a deadly external environment, working a monotonous schedule in an artificial day/night cycle, all under the constant eye of mission control. These conditions erode emotional resilience, increase anxiety and depression, disturb sleep and more. The first two attempts to live in Biosphere 2 were disrupted by interpersonal conflicts and psychological problems among the inhabitants.

Finally, space travel is very expensive and the general public is not enthusiastic about government footing the bill. Even throughout the 1960s Americans didn’t believe Apollo was worth the cost and today (according to a Pew poll) only 18 per cent of people believe that sending astronauts to Mars should be a “top priority”. It will be very difficult to construct viable private-sector business models and space tourism ventures could be wiped out by a single accident.

In summary, significant exploration of space by astronauts will be much further away than popularly assumed.

William Reville is an emeritus professor of biochemistry at UCC