When Scott Kelly returned to Earth, he felt like an old man, he writes in his book. His legs were swollen and aching cruelly, his skin was burning, he was always sick. He had spent almost a whole year on the International Space Station ISS, in February 2016 he landed again on his home planet.
Kelly's return was a stroke of luck not only for his research in space, but also for his twin brother Mark Kelly. The two are so far the only identical astronaut twins. Your genome is almost identical. A comparison between the two therefore reveals what damage the stay in space at Scott has done. First interim results had already been published in March 2018, now there is an official study, which was published in the journal "Science". More than 80 scientists from twelve universities had worked on the project.
All does not harm the health
The result: A longer stay in space does not seem to affect the health and physical condition of astronauts. According to the NASA, most of the deterioration in physical condition that occurred during space-time was reduced after the mission was completed.
This realization is important for future, manned missions such as those to Mars. In space, people are exposed to weightlessness and radiation. How exactly this affects the body and how long any changes remain is so far largely unclear.
All astronauts therefore carry dosimeters that measure the total amount of radiation they were exposed to. If a set maximum is exceeded, her career ends in space - they become ground personnel or divorce. Scott is also retired, but continues to work on projects for Nasa.
For example, genes that control the immune system responded during the All-Outing and for some time afterwards as if the body had been exposed to massive stress, comparable to longer dives or mountaineering. This shows the physical stress of space travel. The structure of the genes themselves, however, remained unchanged. More than 90 percent of the changes also returned to pre-mission levels within six months.
To the surprise of the researchers, the telomere protective caps on the ends of chromosomes grew in space with Scott Kelly. Normally they get shorter with age. But even in this case, most of the changes on Earth disappeared again, some of Scott Kelly's telomeres are now shorter than before the mission.
Grown five centimeters
The health check on his return also showed that Scott Kelly had grown in space by five centimeters. The gravity of the earth, however, reduced it to its normal size after a short time. By contrast, changes in the eyeball were permanent. Among other things, a nerve in the retina became thicker. The mental capacity also decreased in some areas. Staying in space does not necessarily have to be the cause, according to researchers around Francine Garrett-Bakelman from Weill Cornell Medicine in New York. Scott, after all, just got older.
As the scientists continue to report, influenza vaccine works in space as well as on Earth. And the intestinal flora did not change more than it is also observed on Earth under stress conditions.
The study is far from complete, the scientists said. It's still a long way to Mars. On the ISS, the radiation load is only ten times higher than on Earth - in the interplanetary space between Earth and Mars, astronauts would be exposed to a 30-fold dose of radiation.
The health consequences should therefore be more serious on a trip to Mars, emphasizes the biologist Markus Löbrich of the Technical University of Darmstadt, who was not involved in the study. This must be clarified in further investigations, also to develop strategies against it. Nevertheless, the current study brings humanity a little closer to Mars.