Is it actually feasible to populate Mars?
The medical risks of traveling to Mars
Christina Koch will probably not forget March 14, 2019 anytime soon. This Thursday, after years of preparation, the 40-year-old American climbed through a hatch into the orbital module of the Russian spacecraft Soyuz MS-12 on the launch pad of the Baikonur spaceport. In a confined space, Koch took a seat with her colleagues Alexej Ovtschinin and Nick Hague and listened to the countdown of the flight control center - until the three of them left the earth behind them at exactly 8:14 p.m. local time.
Six hours later, the spaceship reached the International Space Station (ISS) on schedule, to the relief of all involved. Only months earlier, with Ovchinin and Hague on board, there had been a false start: the separation of the first from the second rocket stage failed 119 seconds after the start, and the rocket crashed. The passengers were able to make an emergency landing with their space capsule unharmed.
Koch, for whom it is the first mission in space, should make history: She is to remain on the ISS until February 2020 and spend a total of 335 days in space - longer than any woman has ever been before. The record is primarily due to technical reasons. The completion of the new spaceship, with which she is to return to Earth, is delayed. Koch's long stay in space is also of scientific importance: Researchers receive valuable physiological data from a space traveler on a long-term mission. This is extremely important for space medicine - especially with a view to the new challenges that are becoming more and more apparent.
Space travel on the upswing
Several nations have plans to promote manned space travel more strongly after decades of neglect. The most concrete are the plans of the US space agency Nasa, which intends to bring people to the moon again in the coming decade and subsequently also to Mars. Russia, China and the European Space Agency Esa also want to go to the Red Planet, plus private players such as SpaceX and Blue Origin. The usefulness of these projects for astronomical research is questionable, the technical progress and monumental propaganda effect of course not: A successful landing of space travelers on Mars would be the greatest technological masterpiece of mankind - and would make them a multi-planetary species.
Manned trips to our neighboring planet are already technologically conceivable today. Their feasibility has so far failed because of money and the greatest uncertainty factor in manned space travel: humans. The list of known dangers to which space travelers would be exposed on long flights such as to Mars is long - and it is growing all the time. A number of risks that can arise in such ventures have only recently been discovered.
Three years in space
The number of people who have been in space so far is quite manageable at 566. In most cases, medical data was collected and evaluated, and a number of research projects were carried out on the ISS in particular to find out more about the effects of space travel on the body. But while a flight to the space station takes just six hours and the Apollo astronauts traveled to the moon for three days, potential visitors to Mars can expect a much longer flight. If you choose the energetically most favorable route to the red planet, The outward flight alone takes around nine months.
The shortest possible return mission would take almost three years, as one would have to wait for the correct Mars-Earth constellation before a return flight would be possible. Never has a person been in space for so long. The physical consequences of such a trip cannot simply be compared with those of a stay on the ISS. But even these are enormous, as a previously unique twin study by NASA impressively demonstrated in the previous year: the astronaut Scott Kelly spent a total of 340 days in space from March 2015 to March 2016, while his identical twin brother Mark Kelly, also an astronaut, spent a total of 340 days in space Earth stayed. The extensive comparison of their physiological data brought to light a long series of changes that had only occurred in Scott's space and some of which persisted after his return to Earth.
In addition to the long-known effects of weightlessness on bones and muscles, the gene activity in Scott Kelly developed significantly differently, and there was increased damage to the genetic material of the cells. The immune system, the microbial composition in the intestines and the retina of the eyes also changed, while mental performance decreased in some areas. In his 2018 book "Endurance. My Year in Space" (C. Bertelsmann), Scott Kelly wrote that after his return he felt like an old man, with pain in his swollen legs, nausea and burning skin.
Risks and Side Effects
What are the greatest dangers humans would face on a trip to Mars? And what strategies and countermeasures does space medicine have in store to best protect the health of space travelers when traveling to Mars? An overview of the four most important points:
1. Accidents and technical ailments
Even 50 years after the start of manned space travel, rocket accidents and technical malfunctions of all kinds represent a considerable risk in manned space travel. Of the 566 people who have been in space, 18 were killed during their missions; the overall risk is in space to die, therefore at 3.2 percent. Another 13 people had fatal accidents in advance - in accidents during training or during test flights. There is clearly a risk of accidents at all stages of a space flight: rocket explosions during take-off, system failures during the journey, collisions with micrometeors, defective spacesuits, complications when entering the atmosphere or during landing maneuvers - all of this has happened in previous missions, sometimes with mild ones, sometimes with disastrous consequences for the crew.
So far, however, it has never been about a further flight than to the moon. Missions to Mars can neither return prematurely nor count on supplies from Earth in the event of technical incidents. Not even direct communication with Earth is possible in an emergency - the connection is delayed by more than 20 minutes during the flight to the Red Planet.
The spacemen must therefore remain self-sufficient throughout their entire mission. This also applies to care after accidents. Medical training of the crew and an extensive basic set of medicines and equipment for emergency care are clearly an essential prerequisite for manned missions. In particular, on longer flights such as to Mars, the presence of at least one trained doctor on board is urgently advisable.
2. Dangerous radiation
At the top of the list of unsolved problems that space has in store for space travelers is high radiation exposure. While only a fraction of the high-energy particle radiation that comes from the sun and other stars, from supernovae and the vicinity of black holes reaches us on our home planet, thanks to the earth's magnetic field and the dense atmosphere, space travelers are much more exposed to ionizing particles.
For Christina Koch and her colleagues on the ISS, the problem is not as big as it is for potential Mars travelers: The space station orbits our planet in a low earth orbit (the average altitude is 400 kilometers) and receives more cosmic radiation than we do down here on earth. In the Nasa twin study, Scott Kelly found, among other things, increased DNA damage, which is likely to result from the higher radiation. But the ISS is also still protected from the earth's magnetic field.
In the hail of particles
On a flight to Mars, however, this effect disappears, and the high-energy particles cannot easily be shielded by the outer shell of a spaceship. "The problem with cosmic rays is that they just go through conventional protection," says Jens Jordan. "These are heavy ions, and it is even possible that secondary radiation is generated when entering a spaceship, which under certain circumstances can be even more harmful to humans."
Jordan is director of the Institute for Aerospace Medicine at the renowned German Aerospace Center (DLR). It is clear to him: "Radiation is one of the great challenges that we have not yet got under control." If radiation hits the human body, it causes damage to the cells and their DNA. Healthy cells can repair a lot of damage themselves, but only to a certain extent. High doses of ionizing radiation lead to cell death, mutations and, as a result, an increased risk of cancer. Without special precautions, there is a great risk that space travelers will either arrive sick on the Red Planet or not stay healthy there for too long.
"In order to be able to develop solutions for this problem, we have to understand much more precisely what the radiation exposure actually looks like. Only when you know how much radiation is reaching which part of the human body can you assess the risk more precisely and test countermeasures", says Jordan. An important step in this direction is currently being coordinated by DLR: As part of the NASA Artemis 1 mission, the Orion spacecraft developed by NASA and Esa is to fly to the moon in 2021, initially without astronauts. In the passenger seats, however, there should be two "phantoms" - dolls that are equipped with radiation detectors.
Phantoms on board
The 95 centimeter tall dummies "Helga" and "Zohar" have reproduced organs and bones made of plastic with different densities. These have a total of 5600 passive and 16 active detectors, which are supposed to measure with unprecedented accuracy where and how much radiation arrives during the flight to the moon. "The number of female astronauts is getting bigger and bigger, so we decided to use female phantoms for our experiment," says Thomas Berger.
The Austrian heads the Biophysics working group at DLR and is scientifically responsible for the Matroshka Astrorad Radiation Experiment - Mare for short. Except for one difference, the dolls are identical: Zohar will be wearing a new radiation protection vest, Helga will not. A comparison of the data should then show to what extent the vest would protect an astronaut from harmful radiation exposure, at least during moon flights.
It is currently difficult to effectively shield entire spaceships from cosmic rays - their weight would be far too high to be transported into space. The idea of building a protective shield with the help of an artificial magnetic field cannot currently be implemented satisfactorily either.
What other approaches are there? According to the medical doctor Jordan, drug therapies might not help prevent radiation damage, but they can improve the repair of damaged cells. But that is still a long way off at the moment: "At the moment there is unfortunately no substance that I think is the golden ball."
Radiation brain damage
However, an increased risk of cancer is not the only danger posed by the increased radiation doses in the course of a Mars mission. Experiments by US and Russian scientists in recent years have repeatedly provided indications of serious brain damage caused by ionizing radiation. For example, researchers from the University of California, Irvine, reported in the journal "Scientific Reports" in 2016 that even a moderate dose of radiation can cause visible changes in the brain in mice, which are associated with long-lasting memory disorders and behavioral changes. Half a year after the irradiation, the rodents showed signs of confusion and dementia.
In the meantime, at least for this problem, there is a possible solution on the horizon: A team of researchers from the University of California San Francisco recently reported in "Scientific Reports" about a promising active ingredient that could counteract this disastrous effect on the brain. In mice that were first irradiated and then treated with the agent PLX5622 for two weeks, there were no cognitive impairments.
3. Serious microgravity
Probably the most diverse physiological consequences of staying in space are caused by the lack of gravity. If a person is in total or near weightlessness (microgravity), the body immediately begins to adjust to the new circumstances. Within minutes, the body fluids are shifted to the upper half of the body. The neck veins and the face swell and the body tries to compensate for the supposed excess of fluid by excreting more. As a result, the blood volume shrinks.
Aging in fast motion
Unpleasant side effects of this include falling blood pressure, increased body temperature, headache, racing heart, sweating and exhaustion. But after a long time, the body adapts to the new conditions, and astronauts feel better again. "It is very astonishing that humans can survive in such a different environment at all. During the entire course of evolution we were always exposed to gravity," says Jordan.
However, if space travelers are not constantly trying to mitigate the negative effects of the lack of gravity, this has serious consequences. In many ways, the consequences are similar to accelerated aging: muscle mass and bones break down, coordination problems and visual disturbances occur, the cardiovascular system recedes, and the immune system becomes weaker. "It's the opposite of training, so to speak, you are deconditioned," explains Jordan.
The effects on muscles and bones have already been well researched. Our musculoskeletal system reacts quickly to the relief from weightlessness - primarily with degradation processes. Unused muscles atrophy, the bones lose calcium and also shrink. Scott Kelly lost a total of seven percent of his body mass during his one year stay on the ISS. An astonishing detail on the side: At the same time it "grew" by 3.8 centimeters, since the spinal column is stretched due to the lack of gravity. Back on earth, of course, he couldn't look down at his twin brother for long, but quickly shrank back to his normal size.
Deconditioning could lead to considerable difficulties after a long space flight, as injuries and broken bones could result from sudden reloading. On Mars there is only a good third of the earth's gravity, but getting out in full spaceship is still no small matter. The most important measure to counteract the effects on muscles and bones is daily rigorous strength and endurance training, says Jordan. "If you compare that to the past, thanks to the training, astronauts come back from space in astonishingly good shape."
Immune system in a bad way
A worrying complication that, like many astronauts, also occurred with Scott Kelly in space, concerns the eyes: After a long period of time in weightlessness, visual disturbances often occur, in some cases permanent. Accordingly, there is also great research interest in this phenomenon, which could become a serious problem for travelers to Mars, says Jordan: "It has been seen that changes in the fundus of the eye occur in astronauts that look similar to those in patients with increased intracranial pressure. Currently it is assumed that this is due to the volume shift. "
If the intracranial pressure increases permanently on a long mission, not only the eyesight is in danger. In the worst case, there is also a risk of damage to the brain. A possible countermeasure is also being tested at DLR: Artificial gravity through centrifugation could prevent some problems caused by weightlessness, says institute director Jordan. The training plan for Mars visitors is not getting any shorter.
It has long been discussed that microgravity, cosmic radiation and stress during space missions can damage the body's defenses. Just recently, researchers led by Richard Simpson from the University of Arizona investigated how conditions in space affect specific cells of the innate immune system. These so-called NK cells, which belong to the lymphocytes, are able to identify and kill tumor cells or cells infected by viruses - which is particularly important for space travelers who are already at an increased risk of cancer.
Despite the sterile conditions in spacecraft, virus defense is also important for astronauts, says Simpson: "You will hardly catch new cold viruses or flu viruses, but the problem is the pathogens that are already in the body and always become active when one is weakened. "
The sobering result of the study on ISS space travelers who spent at least six months in space: The function of the NK cells is significantly limited, especially in astronauts who are in space for the first time. The twin study with Scott and Mark Kelly also showed that the activity of certain genes related to the immune system changed in space. After all, a flu shot worked just as it did on earth.
4. Stressed psyche
Apart from the dangers outlined above, there is one more factor on which the success of a long space journey depends at least as much: the human psyche. A trip to Mars and back takes about three years - a long time that you have to spend mostly in a confined space with a uniform routine with high levels of tension and always with the same people. Anxiety, stress, depression, loneliness, boredom and conflicts in a team are among the greatest challenges for members of such missions. A premature abandonment of a mission is just as impossible as the direct communication with friends, family or the control center on earth, as they can keep ISS astronauts.
The mental health of the individual participants before the start of the trip is a basic requirement. From simulation studies and polar research missions it can also be deduced how important the composition of the group is. "You not only have to select individuals who can perform certain tasks, you also have to understand how teams work together - over a long period of time and under very demanding conditions," says Jordan. It is known from psychological studies that certain character traits can strengthen the cohesion of a group: above all a sense of responsibility, empathy, sociability and flexibility.
Clown on board
Mixing different personality types is also important: a balance of introverted and extroverted people is just as advisable as the presence of a joker, as anthropologists from the University of Florida were able to show in research groups that wintered at the South Pole. An intelligent clown in the group can significantly counteract tension and act as a link between different camps.
With all the care taken in the selection: Long-term cooperation cannot really be foreseen. That this applies not only to the cooperation within the group, but also to that with the mission leadership on earth, was impressively demonstrated in December 1973. At that time, the three crew members of the US space station Skylab decided without further ado to cut the radio link to earth and Relaxing at the sight of the earth rather than doing the prescribed tasks.
In later investigations into the incident, it became clear that frustration had built up among the astronauts about the high workload. However, they only discussed their anger among themselves, which welded them closer together as a team - and at the same time angered them more strongly against the mission leadership. The "strike in space", which went through all media, was an important lesson for the psychological handling of space travelers - not only for NASA.
Willingness to take risks
One thing is clear: science is by no means under control of all the health risks that threaten a trip to Mars. The risk of astronauts falling ill during the flight, cell and brain damage, impaired vision, deconditioning or falling into psychological crises is considerable - quite apart from the consequences of a stay on the red planet itself.
From today's perspective, would it be completely irresponsible to send people on such a mission? "Whether and when people fly to Mars is not a medical decision," says Jordan. "We can only try to use medical research to assess risks and do everything we can to keep the dangers as low as possible. Whether that is accepted or not is another question - people are ready to take risks . "
Benefit for those who stayed at home
Whenever Homo sapiens makes the leap to become a multiplanetary species, the advances in space medicine are undoubtedly also of earthly importance. Many physical changes that astronauts experience in space also occur in a similar form on Earth - be it due to aging processes, illnesses or accidents. The search for effective countermeasures is by no means only useful to astronauts, and that begins with the development of new examination methods and models for assessing health consequences.
ISS astronaut Christina Koch, however, does not think much about breaking the record for a woman's longest stay in space. "For me it is not the number of days that I am up here that counts, but what I do in that time," she said in a recent interview. But she hopes that her record will also be broken soon: "Because that would mean that we will continue to push the boundaries in space." (David Rennert, November 5, 2019)
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