How do astronomers age in space

Space travel : Twin study shows the consequences of a year in space

A prolonged stay in space does not seem to have a lasting effect on the health and physical condition of astronauts. This was shown by a comparison between the astronaut Scott Kelly, who had lived on the International Space Station for almost a year, with his twin brother, Mark, who remained on Earth. According to the US space agency Nasa, most of the differences that had emerged during the time in space disappeared again after the mission was completed, such as changes in gene activity. The results of the twin study were published in the journal "Science".

Only eight missions lasted longer than 300 days

Between March 2015 and February 2016, Scott Kelly spent almost a year on the International Space Station. He then retired, but continues to do research on his annual mission. In comparison with the twin brother Mark, who was a few minutes older and also a retired astronaut, who remained on the ground during this time, the scientists want to research how long stays in space affect humans. These findings are important for future planned manned missions to Mars.

The results of the current study were drawn up by ten teams consisting of more than 80 scientists and spread across 12 universities. The twin study is unique: a total of more than 550 people have already flown into space, but only eight missions lasted more than 300 days. Scott Kelly stayed 340 days. He and Mark Kelly are also the only identical twin astronauts to date. Before, during and after the annual mission, the two were examined again and again.

Pain, nausea, burning skin

In space, people are exposed to weightlessness and radiation, among other things. How exactly this affects the body and how long any changes persist is largely unclear. In his book "Endurance. My year in space", published in German last year, Scott Kelly described how after his return he felt like an old man, with excruciating pain in his swollen legs, nausea and burning skin.

Scott Kelly's gene activity developed differently in space than his twin brother on Earth, according to the study. Genes related to the immune system were particularly affected. The changes are comparable to those that occur under stress, for example when climbing or diving. The structure of the genes themselves remained unchanged. However, more than 90 percent of the gene activity returned to the level before the mission within six months.

To the surprise of the researchers, Scott Kelly's telomeres - protective caps at the ends of chromosomes - grew in space. Changes in telomere length are associated with aging processes and diseases. In this case, too, most of the changes on earth disappeared again, but some of Scott Kelly's telomeres are now shorter than before.

Radiation exposure higher during Mars flight

Scott Kelly's eyeball also changed, including a nerve in the retina that became thicker. Mental performance also decreased in some areas. The authors of the study led by Francine Garrett-Bakelman from Cornell University in New York made clear that these changes could not only be due to the stay in space.

As the scientists further report, a flu vaccination works in space just as it does on earth. And the intestinal flora did not change more than is observed on earth under stress conditions.

The study was far from over, the scientists said. In a comment, the biologist Markus Löbrich from the Technical University of Darmstadt points out that the radiation exposure during a Mars mission is significantly higher than during stays on the ISS. The health consequences are therefore likely to be partly different. This must be clarified in further studies, also in order to develop strategies against it. Nevertheless, comments Löbrich, the study means "more than just a small step for mankind in this project". (fsch / dpa)

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