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Trapped in space

Some people want to go to the moon and to Mars. The problem is in what condition they would arrive there

Astronauts are like pilots and journalists. What all three professions have in common is that they have a nimbus and a radiance that evaporates upon sober observation. When you think of pilots, you immediately think of smart uniforms, pretty stewardesses and hotels in Cancún, and not of the shift-working airbus driver between Munich and Berlin. The term journalist evokes the Watergate and Pulitzer Prize more than line money and Spiegel Online, more Hersh and Greenwald than Joffe and Reichelt. And astronauts?

Starwars. Star Trek. 2001 - A Space Odyssey. Lem's masterpieces. Strange worlds. Great battles. Infinite spaces of the possible. "Gigantic ships that were on fire, outside Orion's shoulder. [...] C-Beams [...], glittering in the dark, near the Tannhauser Gate." Countless tales of exploration and adventure, of beauty, wonder and heroism. How does reality hold up against it?

The universe: no place to go for a walk

As I write these lines, I am at a conference of the German Aerospace Center (DLR), because a strange fate has landed me in space research. The universe is the most extreme of all environments. According to the Hitchhiker's Guide, humans can survive in it for thirty seconds (holding their breath), and that should be an exaggeration. We cannot stay in space unprotected; we need the cases and capsules. But even these are more characterized by what they lack than what they offer.

Gravity. Protection from space radiation. Move. Day-and-night rhythm. Green. Social homeostasis. Man needs all of this for wellbeing. As it were ex negativo Space aircraft illustrate how much humans with all their body parts - and especially with their brains - are dependent on their environment.

Nonetheless, all space nations, as well as Elon Musk and Jeff Bezos' companies, plan to return to the moon within the next two decades, and to bring humans to Mars within this century. One dreams of building a permanently inhabited base on the moon, and from there to advance to our neighboring planet. Humans would then be in space longer than ever before, and they would leave Earth's magnetic shield for the first time since the Apollo program. What does this mean for future astronauts?

Streaked with ions

The International Space Station (ISS) conveys an idea of ​​this, but hardly any more. Since it is in the lower earth orbit, it still enjoys the protection of the earth's magnetic field from cosmic rays, the effect of which we are investigating at the Helmholtz Center for Heavy Ion Research.

Astronauts on the ISS receive the permitted annual radiation dose for employees (20 milliSievert) within one month; But that is nothing compared to the estimated 1 Sievert that Mars travelers would have to take. The radiation continuously shoots through the body like tiny pellets and disintegrates all the large molecules it encounters - including and especially DNA. This not only increases the risk of cancer - which would almost be a guarantee for travelers on Mars. It also causes countless small infections that are used to repair radiation damage. In the brain, the inflammation reduces the efficiency of the neurons.

A few years ago, the so-called NASA twin study showed that this is not just a theoretical problem. It took advantage of the fact that astronaut Scott Kelly, who had spent almost a year on the ISS since March 2015, has an identical twin brother, Mark, who stayed on Earth. The change in numerous biological parameters before, during and after the flight time was examined in parallel for both. Those that were permanently changed include the mental accuracy and speed, which in Scott's case surprisingly only decreased after landing and remained lowered for the observation period of six months.

Well, identical genes or not, a sample of 1 is not very conclusive. But animal experiments support the concerns. When mice are experimentally exposed to relatively high doses of radiation, their learning ability and memory suffer, there is chronic inflammation in the brain, and the shape of the neurons changes. But the doses used in this study were significantly higher than what an astronaut would have to expect.

Only recently, the research group led by Charles Limoli (University of California), who is leading in this field, investigated what happens when mice are treated like Martians, i.e. with mixed radiation of low intensity over a period of six months. The findings confirm the concern: In the hippocampus, the nerve cells become less active and less capable of learning, and this is propagated into the animals' ability to learn. They have difficulty memorizing things and places and avoid contact with their own kind. If you can transfer this from mice to humans and extrapolate it to a two-year mission to Mars, the astronauts would arrive there as drooling idiots. And there is no solution to the problem in sight, because shields are always heavy.

Completely detached from the earth. . .

As I said, this problem does not arise on the ISS. Others, on the other hand, can be observed there, albeit in a small sample and with almost no opportunity to try out countermeasures. For example weightlessness. A dream for many people, it becomes a problem in the long run. The muscles break down, the bone density decreases. The cardiovascular system is also changing, because the large amount of blood that normally sinks into the vein reserves of the legs flows freely through the upper body in space; to compensate for this, the body reduces the amount of blood. The immune system changes, loses performance. ISS astronauts often suffer from minor infections, and herpes breaks out reliably.

Which of these is due to the weightlessness, which is due to the tightness, which is due to the lack of sleep? It is instructive which model paradigms scientists use to investigate the causes and possible control of these effects in larger numbers of test persons on earth.

Weightlessness, for example, can be imitated in parabolic flights, even if only for around 20 to 30 seconds. In this short period of time, according to a surprising finding by Stefan Schneider from Cologne, the ability to think improves a little. This can possibly be explained by the fact that the excitability of the nerve cells increases slightly, because a lower amplitude was also observed in the EEG.

Disoriented through space

In the long term, however, it could look different. So far, there is little data from astronauts and therefore from real weightlessness. While older studies focused primarily on the movement and equilibrium system, there has so far been a more recent study of ten cosmonauts who were pushed into the magnetic resonance tomograph immediately after an average of six months in the ISS and several months afterwards. It turned out that staying in the flying aluminum can not only affects motor skills: in large areas of the brain, especially those with spatial orientation (hippocampus, temporal lobe), and surprisingly also in all main nodes of the resting state network (occupied with the self-image) , the thickness of the cerebral cortex decreased, and also did not recover in the temporal lobe within the observation period.

Since real astronauts are rare, researchers are content with all kinds of substitute personnel. For example, the winterers at the Antarctic stations are popular at DLR. You will experience gravity, but little more than the ISS crew: being locked in, being confined, lacking a day-night rhythm and social stress are their everyday lives. The result here too: The gray matter in the hippocampus becomes thinner.

Another model are test persons who agree to spend weeks and sometimes months in "head down bed rest": Lying in bed with the head end tilted 6 ° to 12 ° down to imitate how the blood flows into the under weightlessness Head rises. They too are subject to gravity, but never move against it. It is not surprising that mental fitness also dwindles with their physical fitness, which can also be seen in the brain, and that they deteriorate over time in various thinking tests.

Most of the impairments disappear after a while when the experiment is stopped. They are simply adaptations, witnesses to the great plasticity of the brain: it adapts its abilities to the environment in which it is currently located. In bed, on the ISS or in an Antarctic station (there even literally), this environment is what researchers use the chic acronym ICE for: isolated confined extreme. Without the social and cognitive stimulation, the extensive movement, the natural stimuli that the brain needs to function properly, it breaks down like a muscle in a cast.

Then rather at night in Stammheim

The scientists who study the conditions of space flight are therefore under no illusions: The interior of a spaceship is not a first-class flight, it is not even economy. Terrestrial space flight analogues are therefore as unpleasant situations as lying still for weeks, like wintering in Antarctica.

In conversation I suggested another model that is surprisingly little researched: prison inmates. Lack of exercise, cramped, low-stimulus space, social isolation, and - keyword: bed rest - the inclination of prisoners to lie in bed an average of six hours during waking hours (!). Conditions in prisons are similar to those on the ISS, and in fact what appears to be the only long-term study of inmates shows that cognition is declining. Wouldn't one have here a literally obvious, at the same time inexpensive model of space travel, with countless test subjects?

But my interlocutor contradicted: His father works in the JVA Stammheim (yes, of all things). My counterpart really raved about training programs, outdoor activities, times with open cell doors for mutual visits, rehabilitation measures. At least in German prisons, we finally agreed, the prisoners are far better off than astronauts in space.

But the nimbus remains. (Konrad Lehmann)

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