Radiation, the invisible threat to the colonisation of Mars

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Jesús Ordoño FernándezIMDEA MATERIALES

The exploration of the red planet faces numerous challenges, from the effects of microgravity to space fungi and one of the most dangerous: radiation.

The latter mainly comes from two sources: the Sun (and its solar storms) and outer space, distant galaxies, stars, and supernovas. Solar storms are very difficult to predict and release huge amounts of radiation in a very short time, mainly in the form of protons. On the surface of our planet, they produce beautiful auroras in the sky. But in outer space, they can be lethal.

For example, in August 1972, between Apollo missions 16 and 17, a series of these very powerful storms caused problems and failures in satellites and communication systems on Earth. Fortunately, no astronauts were in space at that time, as they possibly would not have survived.

On the other hand, space radiation is a constant threat. It also consists mainly of protons but also contains heavy elements such as helium or iron, which are much more dangerous and energetic. These are capable of disintegrating the atoms of the material they collide with, whether it be the metal walls of a spacecraft, a satellite, or a person. In the process, they generate a cascade of subatomic particles or very harmful secondary radiation. This is what is known as cosmic rays.

Thanks to the protective atmosphere and the magnetic field, on Earth, we are shielded from this assault. However, on a future trip to Mars, astronauts will be exposed to a quantity 700 times greater than what reaches our planet. A single day in space equals the radiation received on the Earth’s surface during an entire year. The effects this would have on humans are uncertain and difficult to assess.

Detector HADES at the GSI Helmholtz Center for Heavy Ion Research in Germany, the only European center capable of simulating cosmic rays. Photo: Jesús Ordoño.

It could cause serious damage to many tissues depending on the dose received. Among other things, it could cause cataracts, dermatitis, sterility, affect memory and the nervous system, cardiovascular problems, even permanent mutations in their DNA and cancer.

Therefore, more research is needed to protect astronauts, such as that carried out at the GSI Helmholtz Centre for Heavy Ion Research in Germany, the only one in Europe capable of simulating cosmic rays.

In Search of Radiation-Resistant Materials

In general, the best protection consists of sheltering behind thick walls or protective screens, such as a concrete wall or the lead aprons worn by radiologists.

The problem is the high weight that would be involved in manufacturing spacecraft from these materials. Instead, aluminum, much lighter, is usually used. However, although shielding behind a panel of this metal may protect against much of the low-energy radiation, such as most protons, the heavier and more energetic elements would penetrate it, damaging the structure and reaching the astronauts inside the spacecraft.

In case of a significant solar event, astronauts aboard the International Space Station must take refuge in more shielded areas of the spacecraft, such as the Russian module Zvezda (pictured). NASA / Wikimedia Commons, CC BY

Thus, in view of a future mission to Mars, it is necessary to develop much more efficient materials. Among them, due to their small size and low atomic number, those with a high hydrogen content are possible options.

Water, for example, could be strategically stored in the walls of the spacecraft to create a kind of shield. Unfortunately, this is an extremely scarce resource in space, and using it as a construction element would be a waste.

Polyethylene, the same plastic found in water bottles or shopping bags, or Kevlar, the synthetic fiber used in bulletproof vests, are other promising candidates. Due to their high hydrogen content, they can reduce the radiation dose by up to 30%.

Imitating Nature’s Solutions

On Earth, there are many organisms that are resistant to radiation, especially certain radiotrophic fungi that have grown in Chernobyl, such as Cladosporium sphaerospermum. Some researchers suggest that we could use them as a living shield for space travelers.

Experiments conducted on the International Space Station revealed that only 1.7 millimeters of this fungus are sufficient to reduce nearly 1% of radiation. Furthermore, it is an organism that uses radiation to grow, in a process called radiosynthesis, so its protective function could increase as the space mission progresses.

Cladosporium sphaerospermum after 14 days of cultivation at 25 degrees. Medmyco/Wikimedia Commons, CC BY

Other organisms rely on melanin, a molecule that in humans gives color to the skin, eyes, and hair, and also offers a shield against the sun’s rays. Being flexible and lightweight, its use as a biomaterial for application on the astronauts’ skin as a sunscreen or even on the structure of the spacecraft is being considered.

Protective Magnetic Bubbles

Similarly, some scientists are exploring the possibility of generating magnetic fields similar to the one that protects the Earth. Projects like CERN’s SR2S or NASA’s CREWHat are working on a design of superconducting magnetic coils capable of generating a magnetic field around the spacecraft to deflect up to 50% of harmful cosmic rays.

Additionally, we have drugs to treat radiation exposure, not only for astronauts but also for potential accidents on Earth, for example, in nuclear power plants, medical or research facilities, or in other radiological or nuclear emergency situations. Some examples are stable iodine, cytokines or chelators, and products to remove radioactive substances.

Thus, on a future trip to Mars, protection against harmful cosmic particles will come from a combination of different solutions, some based on technology we already have and others, perhaps, on innovative ideas we haven’t yet thought of.

Jesús Ordoño Fernández, Postdoctoral Researcher, Tissue Engineering and Biomaterials, IMDEA MATERIALS.
This article was originally published in The Conversation. Read the original.

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