How Can the Martian (really) Survive?


Raşit Gürdilek

Technology racing against time

First, he has to change his stylist! Joking aside, we shall treat the matter of suits later on, but with the flashy, body-wrapping  patchwork garment like that of the eager kid who received his first motorcycle on his birthday, you cannot walk around on harsh Martian terrain which bears no resemblance to a film plateau.

For, let alone Mars, just ascending a few tens of kilometers above the Earth, we encounter conditions hostile to life. Freezing cold is the first worry. To be able to to preserve the body temperature, suits fashioned with  hi-tech materials and life support equipment are needed.

 Human body is made for Earth

Another problem is the changes the weightless environment called “microgravity” causes to our bones, muscles and physiology whose evolution were tuned to Earth’s gravity of 9.80665 m/s2 . Topping the list are reduced bone density and serious levels of muscle loss. While the bone density decreases by 1 percent a year due to the depletion of minerals, the rate is expected to be 1 percent a month for the Mars astronauts. Furthermore, since the bone density cannot be restored to former levels on return to Earth, brittle bones and possible fractures are among the problems for which solutions are sought.

Since movement is not difficult in weightless or reduced gravity environments, muscles evolved in accord with Earth’s gravity undergo serious losses. Astronauts on long-term missions aboard the  International Space Station (ISS) partially offset  these effects by exercising regularly, and Mars has gravity, albeit a third of that of the Earth. So, Mars astronauts and colonists will not hop around like the astronauts do on the Moon whose gravity is only a sixth of the Earth’s. Still, the effects of microgravity on human physiognomy and physiology are not fully understood and are subjects of serious research.  Passage from Earth’s gravity, first to weightlessness and then to an environment  of reduced gravity, affects orientation, eye-head and eye-hand coordination, balance and walking. And  since body fluids tend to migrate upwards in micro and reduced gravity environments, pressure increases in the eyes, affecting vision. Loss of water and calcium from the bones trigger formation of kidney stones. These and the impaired attention and slowed down cognitive abilities dubbed “space fog” reported by returning astronauts after extended stays on the ISS, emerge as problems which need to be tackled on long-duration missions like the trip to Mars.

Ever spent 900 days with someone in the same room?

We do not list the psychological problems likely to be caused by living together for extended periods in the stressful  atmosphere of difficult and tiring tasks and constant threats within a cramped spacecraft or small modules passing for “houses” on Mars. The Mars day or “sol” which is 38 minutes shorter than that of the Earth means a disrupted circadian rythm, which, together with other factors such as pervasive noise, heavy workload and monotony, can play on the nerves and cause serious frictions that may jeopardise the mission. Hence the astronauts have to be chosen with utmost care and trained to cope with such contingencies. Provision of adequate medical expertise to the astronauts to enable them to intervene in chronic or emergency situations is in the list of mission planners. Tuning the circadian rythm to the new day-night cycle by LED lighting is also among the contemplated measures. NASA and the European Space Agency ESA are conducting experiments in which candidate astronauts or volunteers spend long periods in isolation to prime the would-be Mars explorers for the abrasive psychological environment to minimize the risks. In one such experiment (Mars-500) carried five years ago, six volunteers were confined to a simulated living quarters without access to the outside world.

 It is known that long time exposure to microgravity weakens the body’s immune system. Another problem the astronauts on long-duration Mars missions and future colonists will have  to face is premature  aging, since the structures called telomeres at  the ends of chromosomes associated with the length of lifespan are thought to get shortened under the bombardment of cosmic rays in the space environment.

Tried out at the ISS

In the list of  solutions NASA has drawn up for these problems are pressure cuffs to be worn on legs to prevent the migration of blood and lympathic fluids to the upper part of the body and cause vision problems, use of potassium citrate or similar drugs against the risk of kidney stones and biophosphonates to prevent the bone loss.

Another platform NASA experts use to test solutions for expected problems on Mars, is the International Space Station. Health and physiology parameters of astronauts who spend more than six months in the microgravity environment of the ISS are regularly monitored and technologies and experiments designed to address the long list of potential problems are tried out. A successful experiment has been growing edible vegetables under LED lights.

Small is powerful (and dangerous)...

But the most important and difficult problem astronauts (and future colonists) will have to cope with during the voyage to Mars and their stay there is the hazardous “ionizing radiation”  in space. Ionizing radiation is made of subatomic particles like electrons and protons which carry electric harge and ions or atoms which have lost some or all of  their electrons and become charged. This radiation has two main sources: the sun and cosmic rays coming from all directions in space. The sun has been spewing charged particles from its surface to space for billions of years. These are positively charged protons which actually are hydrogen nuclei, alpha particles or helium nuclei, and negatively charged electrons stripped by heat from hydrogen and other, heavier atoms synthesized at the core and rising to the surface. This steady flux of particles in every direction called the “solar wind” naturally comes on the Earth, too. But the strong magnetic field of our planet acts as a shield preventing most of these particles from reaching the surface. Since they have relativley low energies, particles in  the solar wind do not pose a threat to astronauts or sensitive electronic equipment  aboard the spacecraft since they cannot penetrate their aluminium skins and plastic lining. The problem arises when they are accelerated!

Protecting the Earth, yet...

There are two basic causes accelerating electrically charged particles:magnetic fields and solar flares. The charged particles carried by the solar wind and whipped to speeds between 200 and 1000 kilometers per second and the extrasolar cosmic rays are accelerated by two concentric, torus-shaped structures called “Van Allen belts” girdling the Earth, to high energies which pose a threat for the astronauts and their crafts.

The inner belt, rising from 1000 to 6000 km above the Earth, is primarily composed of protons with some additional electrons, also called “beta particles” and helium nuclei, or “alpha particles.” The outer belt, from 13.000 to 60.000 kilometers, is almost exclusively made of electrons. Within both belts, particles zip around in chaotic trajectories. Their velocities and energies vary according to the dynamics of the Earth’s magnetic field lines and the magnetic activity on the sun.

American astronauts sent to the moon in 1969 and throughout 1970s had safely passed through these belts, but the varying strength of the radiation and the fact that Mars astronauts will be cut off from medical observation and care from the Earth for long periods cause worry to the planners of the manned exploration of Mars.

Sun’s power displays

Beyond the Van Allen belts, one of the greater hazards astronauts and Mars colonists will be exposed to is the “coronal mass ejections” (CME) from the sun. As a result of particularly strong magnetic storms occuring in the sun’s outer atmosphere called the corona, huge plasma clouds  containing billionsof tons of charged particles are ejected into space. Traveling at relativistic speeds, these particles easily penetrate the aluminum skins of the spacecraft. These highly energetic particles also interact with atoms in the skins of the spacecraft and cause a dangerous particle flux called “secondary radiation” mostly made of neutrons.

Real threat

Finally, the biggest and continuous hazard the Mars explorers and settlers will have to cope with is the high-energy charged particles called “galactic cosmic rays” coming from stars in the Milky Way and even from other galaxies.

Galactic cosmic rays or the galactic cosmic radiation flux falling into the Solar System is chiefly made of energetic protons (86%), helium nuclei (11%), electrons (2%)  the rest being ions of heavy elements and positrons, which are the positively charged antimatter of electrons.

Solar radiation, which extends far beyond the planets, affect this flux. The sun’s magnetic activity follows an 11-year cycle. The strength of the magnetic field, reaching its apex  in the stage called “solar maximum” when the number of sunspots becomes highest, acts as a shield which deflects relatively less energetic  of the galactic cosmic rays. The “solar minimum” with least number of spots is the stage when the Sun’s magnetic field weakens and the cosmic ray flux increases. But while the solar maximum partly reins in the cosmic ray flux, it is also the stage when the CMEs reach highest numbers. Since the cosmic rays pose a greater and more continuous threat than the unpredictable CMEs, these solar cycles have to be taken into account in the planning of manned Mars missions.

These cosmic ray particles, chiefly made of protons and partly of heaviy ions produced in supernova explosionsare whipped up to great sspeeds and energies by the interstellar magnetic fields. And when they hit atoms, they interact in strengths commensurate with th12444444441eir energies, causing a broad spectrum of secondary particle jets. As can be guessed, the greatest hazard from the primary and secondary radiation to the human organism is cancer.

How does it affect?

When cosmic ray particles strike stable nuclei, they split them into usually radioactive isotopes of elements with smaller masses. Easily penetrating the skin to drive deep into body tissues, high energy protons as well as neutrons and other secondary radiation particles produced by the fission not only cause damage to cell walls and fluids, but also interact with the atoms in the DNA molecules on the chromosomes in the cell nuclei, causing gaps, interrupted sequences and mutations on the DNA strands. If these mutations cluster together on the strands, they cannot be corrected by the DNA’s repair mechanism and may cause cancers in the years ahead. Exposure to radiation in vey high doses and intensities may cause often fatal acute radiation sickness. Besides the DNA damage, intense radiation also causes the formation of reactive oxygen isotopes in  the body, thereby increasing the risk of cancer.

Although the level of the risks for human health posed by cosmic radiation depends on many variables such as the volume of the flux, the energy of the particles, stages of he solar cycle etc, according to the data gathered by a spacecraft sent to Mars in 2001 to study the radiation environment there (MARIE), a person unprotected by a shield in the interplanetary medium, will acquire 400-900 milisieverts (mSv) of radiation per  year. In comparison, 1 mSv is the radiation dose a person will acquire through three chest X-rays. And the average annual radiation humans are exposed to is 2.5 mSv.

Even if they are protected by a radiation shield, the radiation dose astronauts will acquire on a Mars mission, including 12 months of space travel going there and comig back and 18 months on the ground, is calculated to be 500-1000 mSv, which is close to the lower end of the 1-4.5 sievert limit set by the National Council for Radiation Protection and Measurements for the whole career of astronauts on low Earth orbit missions.

 Apart from the cancer threat, declining cognitive abilities and motor functions as a result of damage from cosmic rays to the central nervous system, as well as cataract formation in the eyes and cardiovascular problems are risks to be taken into account.

Natural and artificial shields

As Mars has cooled much earlier because of its small mass which is a tenth of the Earth’s, it’s solidified iron core is not surrounded by an outer core of liquid iron like that of the Earth in which the motion of electrically charged ionized atoms creates a dynamo effect. It, terefore, lacks a global magnetic field which screens the radiation flux, at least partly . Instead, it has small, localized magnetic fields. What’s more, density of its atmosphere is less than 1 percent of Earth’s. In other words,it is wide open tothe devastating effects of cosmic radiation.

Focused on a program which aims to send astronauts to Mars in 2030s, NASA is working on technologies which would remove, or at least diminish the risks and enable the astronauts and pioneer settlers to survive and conduct research in the harsh Martian environment.

The most urgent need is providing a reliable protection against dangerous space radiation.  According to NASA scientists and technicians, this can be done in  two ways: Either thickening the shield, or making it from a better material.

As thicker walls in spacecraft carrying the astrınauts and habitats to be established on Mars means heavier loads and hence prohibitive costs and insurmountable engineering problems, they can be ruled out as an option.

As for the better material, the key for that is the principle that the best defense against the threatening particle is countering it with a particle of similar mass. Since greatest danger is posed by protons, the identity of the natural defensive weapon becomes obvious: hydrogen.

In its lightest configuration, the hydrogen atom is composed of a single proton and a single electron and is the most abundant element in the universe. Hence, it provides protection against both the high-energy protons in the cosmic ray flux, and the neutrons (of nearly identical mass) in the secondary radiation they cause.

Hydrogen is also abundant in water and polyethylen,  the material for plastic water bottles. There’s also the liquid hydrogen fuel which the spacecraft use for manouvering.  Therefore, water tanks in spacecraft and in Mars habitats could be positioned as a shield against radiation (especially over the sleeping quarters and galleys)  and depleted water can be recycled and stored again. The water and fuel Mars astronauts and colonists will obtain from local sources may also be positioned as additional shields.

Boron is the right stuff!

Since thicker polyethylen lining inside the aluminum walls of the spacecraft will increase the weight that would require more rocket power, NASA researchers are concentrating their efforts on lighter and stronger materials that can shield radiation. One is hydrogenated boron nitrade nanotubes, or more commonly, hydrogenated BNNTs. These are nanoscale structures made of carbon, boron and nitrogen. Hydrogen is placed in the cavities between the nanotubes. Since boron is a very good absorber of neutrons in the secondary radiation, it makes the BNNTss an ideal material for shielding inside the spacecraft. As NASA technicians have now succeeded in making fabrics out of the BNNTs, they can be used as ideal lining material for the spacecraft’s walls. 

Hafnium ,which is among the materials used in control rods which tune the intensity of fission reactions inside nuclear reactors,  is also an efficient neutron absorber. So, hafnium compounds are also among contemplated materials for radiation shields. 

Portable magnetic fields!

A more radical idea for sparing the astronauts at least from the galactic cosmic radiation particles with relatively lower energies is “active shielding”  which foresees the protection of spacecraft with magnets, high  voltages, or even with their own magnetospheres. But the cost of the necesssary equipment, the power scales required by active shield materials and their weights as well as large volumes involved, take them out of the list of realizable projectsat least for the near future. 

Yet, NASA has not given up totally on the technologies on the borderline between science and science fiction, designing  structures using superconducting magnets with a view to future use of active shields. In this context, NASA Innovative Advanced Concepts – NIAC at the Johnson Space Center, is working together with the Florida-based superconductors manufacturer  Advanced Magnet Lab – AML on an active shield project. The shield, of which AML engineers have developed a scaled-down prototype, is based on inflatable magnets which surround the habitat unit of the spacecraft. The magnetic sheet (resembling magnetic tapes used in old recorders), superconducting at the “high temperature!” of -183°C, will be pasted on an extremely thin but strong material called kevlar, which will be folded around long cylinders. A current, encountering no resistance when applied to the cylinder and making use of the Lorentz force which creates a magnetic field perpendicular to the direction of current,  will cause the folded kevlar case to inflate and become a magnet of eight-meter diameter. While the six inflatable magnets form a shield against cosmic radiation, the seventh wrapping the habitat module will serve as another active shield protecting the magnetic fields within the module itself.  

“Suit” did you say?

Suppose the spacecraft  has touched down on Mars. There the astronauts will need suits in which they can work or explore outside their relatively protected habitats, or rovers they ride on long excursions. 

NASA experts underline the fact that, a spacesuit is far from being a heavy parka you can simply take out of a wardrobeto put on as the word “suit” implies.

For as they work on Mars surface, their suits will have to protect the astronauts  from the cold and radiation while at the same time supplying the air and water they need. They will also provide the outside pressure which should counterbalance the body’s inner pressure tuned to the atmospheric pressure on Earth. They also have to be flexible enough allowing astronauts to kneel and use their hands and fingers with  ease. Therefore from the drawing board to the first prototypes, the development of a space suit takes three to four years.

The latest candidate which has come on the catwalk in hopes of being chosen for the space wardrobe is the suit called “NDX-1” (North Dakota Experimental – 1). It is developed by the North Dakota University Manned Spaceflight Laboratory and is relatively more flexible compared to others.  Pablo de Leon, who leads the team which developed  the suit says suit is not a suitable name for these. “Confining  a human is a very complex task.  Therefore the suit we have developed is in fact a miniaturized spacecraft, which also has to be flexible and comfortable, will not hamper your work. That is something far beyond a machine.”

Video:  https://www.youtube.com/watch?v=CUOxK_sqzmw

NASA planners and technicians are working together with universities and private companies on different prototypes marked for different environments.

One of these, the Prototype Exploration Suit  (PXS), has been developed to be worn by astronauts for extravehicular activities (EVAs) at zero or microgravity environments at low Earth Orbit (up to 500 kilomerers above the Earth) as they work on  the assembly of spacecraft which will ferry astronauts and supplies to Mars in accord with NASA’s current plans.  The suit can be pressurized and the 3-D printing  tecchnique used in its production will allow the astronauts to produce their own suits tailored to their measurements, during the voyage. To provide more freedom of movement compared to the suits worn during EVAs outside the ISS, it carries fewer instruments.

The spacesuit NASA has commissioned for activities at airless and reduced pressure environment outside the habitats and pressurized rovers is called Z-2. The suit, which features a hard composite upper torso in contrast to the earlier “soft”  Z-1 model, can be entered from a window fixed to its back. This releases the astronauts from the necessity of entering a highly pressurised chamber called aairlock to prevent the air from escaping , before entering the suit directly by passing through a hatch on a panel called a suitport. Designed to prevent maximum ability of movement for the asstronauts  can be arranged for different body sizes from the shoulders and the waist. Weighing 65 kilos (on Earth) passes as “light” compared to others. But since the Martian gravity is about a third of the Earth’s , the astronauts wearing it weill feel themselves as carrying the load of an ordinary soldier.

The Portable Life Support Systems (PLSS) to be mounted on spacesuits during surface exploration or EVAs during voyages have also been renewed. The PLSS  developed for Z-2 has an oxygen regulation mechanism sporting 84 different options. The PLSS which can regulate the level of moisture within the suit, the carbon dioxide removal mechanism renews itself instantly when simply held in vacuum instead of the required 14 hours by the older models.

These prototype suits are at present serve as platforms for experiments and are not ready to be worn either in space or on Mars.  After the completion of necessary experiments and improvements, the final models are expected to be produced and tested by 2020.

Would you like tomatoes?..

In “The Martian”, astronaut-botanist survives his solitary forced stay by cultivating potatoes in the soil which he cultivates with his own “solid refuse”. But in view of experts, Mars farming poses hard challenges the astronauts and potential settlers will have to tackle.

Because, like us humans,  the plants we grow or harvest are also evolved inconformity with the conditions on Earth. With the exception of carbon dioxide, the things required for growing plants either do not exist on Mars or are in very limited supply. And those that do exist are different  than their Earthly counterparts. For photosynthesis, plants require, oxygen and water besides carbon dioxide, a suitable soil from which they can draw water with  their roots, a light source to provide energy and specific air temperatures. These are all available on Earth. And the Earth soil is full of nutritious substances like nitrogen. But the nitrogen in the air and soil is not useful for plants. Therefore, plants can use this nitrogen after turning it first into a benefiicial form (reactive nitrogen) before using it.

Whereas the Earth’s atmosphere is largely composed of nitrogen(78%) and oxygen(21%) Mars 

atmosphere is almost exclusively (95.3%) made of carbondioxide, with only a negligible (2.7%) presence of nitrogen. As for its soil, it is mainly  regolith,  a powdered form like the Lunar soil, blown by winds and hardly able to hold water. The nitrogen is in very little supply. As for water, Rovers NASA has landed on Mars have found that Mars soil was rich in water, which, however, is pretty briny. There’s another problem: The density of the Martian atmosphere is less than 1 percent of the Earth’s. So, since there is not enough atmospheric pressure to keep the water in liquid form, normally water can exist only as gas or ice. But because the abundance of mineral salts called perchlorates found in Martian water samples drops the freezing point, liquid water can exist on surface in episodes when the temperatures rise above -23°C (during summers in the equatorial belt).   

(See:  https://kurious.ku.edu.tr/sites/kurious.ku.edu.tr/files//surface_water_flowing_on_mars_-_astronomy_-_pdf.pdf   )

But unfortunately perchlorates negatively affect the growth of plants and may cause health problems in humans.

Yet, the results of an experiment (Published inthe open access PLOS ONE Website) carried out by Dutch scientists with 16 different plants on simulants of Lunar and Martian regoliths and low-quality Earth soil, have shown that several  plants, including tomato, wheat, carrot and cress, can grow on Mars soil even without the use of nutrients. The researchers note that oxygen-fixing legume varieties used in the experiment can seed the soil with reactive nitrogen and that the soil can be further enriched by the use of some sturdy grass species as green manure along the feces of the settlers. But since the experiment had been conducted under atmosphere, climate, light and pressure conditions specific to the Earth, these conditions have to be created in greenhouses or plastic tents to be set up by astronauts or the colonists on Mars.

At the Mars Desert Research Station at Utah, U.S., volunteers directed by researchers conduct experiments with a broad range of species, from local desert plants to hops, on Mars soil samples designed in accord with data gathered from Mars by Viking landers in 1970s. And researchers at Canada’a Guelph University, carry out similar experiments  under “Martian atmospheric and climatic conditions.”

But botanist Paul Sokoloff of the Canadian Museum of  Nature believes it will be much more difficult to grow plants in real Mars environment, at least initially, outside  the protected, greenhouses with controlled air and temperature.  According to the researcher, “terraforming” Mars to make it look like Earth by thickening its atmosphere by seeding the planet with cyanobacteria which absorb carbon dioxide and produce oxygen will not only take hundreds of years, its success will be dubious in view of the far stronger eroding effect of the solar wind.

Fuel is in the air and soil...

At the end of the mission, the astronauts will have to return to their vibrant home planet they would have missed dearly. For that, they will need fuel. Future settlers will also need an abundant and dependable energy source.  So, one of the first things the astronauts will have to do after setting foot on Mars will be producing the liquid methane-liquid  oxygen fuel for the ascent craft which will take them to the spacecraft parked at the orbit for the return trip to Earth. They will do that at the reactor   ̶  which would have been landed on the planet before their arrival   ̶  through the reaction between the carbon dioxide from the Martian atmosphere and the liquid hydrogen they had brought with them. But as they would have to initiate the process immediately after arrival, the facility will initially run on nuclear power.

The  Martian atmosphere is composed of carbon dioxide (95.3%), nitrogen (2.7%), argon (1.6%), oxygen (0.13%), carbon monoxide (0.08%) and trace amounts of water vapor, nitrogen oxide, neon, krypton and xenon. No hydrogen worth mention exists in  the atmosphere. But even if they lose the liquid hydrogen they had brought along, they can extract hydrogen  from the water ice whose abundance under the surface and the polar regions had been established by spacecraft in Mars orbit or mobile laboratories on the surface.

In the fuel production facility, astronauts will synthesize methane fuel by reacting liquid hydrogen with atmpospheric carbon dioxide through a method called the “Sabatier process” and will obtain water as a bonus.  The Sabatier process yields 2 tons of methane and 4.5 tons of water for every ton of hydrogen. While the methane is cooled and strored, the water will be split by electrolysis to hydrogen and oxygen which will be used both as fuel and breathable air in the habitats. Through electrolysis, 4.5 tons of water yields  4 tons of oxygen and 0.5 ton of hydrogen. As the oxygen is cooled and stored, hydrogen is  re-routed into the Sabatier cycle. But since larger volumes of oxygen is needed for the liquid  methane/liquid oxygen fuel (3.5 tons of oxygen is required to burn a ton of methane), atmospheric carbon dioxide will be split into oxygen  and carbon monoxide through superheated zircon cells. Carbon monoxide will be fed back to the atmosphere, oxygen will bestored in cooled tanks.

A ll these attest to the meticulous planning and preparations undertaken to enable the man  to set foot on Mars. But like in all plans, chance is an  unpredictable factor. The operation, resting  on critical balances, may be compromised by something that goes wrong in one of its components, imperiling our brave pioneers who have taken on the task of opening the doors of a new home for the mankind.

Then, all will be left to the creativity and imagination of the “Martians” like Mark Watney alias Matt Damon. 

REFERENCES

  • 1. “Real Martians: How to Protect Astronauts from Space Radiation on Mars”, NASA, 30 Eylül 2015
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  • 5. “Cosmic raditionhttp://www.skybrary.aero/index.php/Cosmic_Radiation
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  • 7. “NASA Unveils New Mars Space Suits”, IFLSCIENCE!, 12 Novembre 2015 https://www.youtube.com/watch?v=CUOxK_sqzmw
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