06 Febrero 2017 18:28
Last March, astronauts Scott and Mark Kelly, 52-year-old twins, completed their mission. Scott landed after 340 days in space, while Mark, who this time had remained on Earth, embraced his identical twin.
The mission, named 'The Twins Study', had one very clear objective: to discover what happens to the human body after a year in space, floating in microgravity. Since Scott and Mark are twins, they were the ideal choice. Scientists studied data from before, during and after astronaut Scott Kelly's mission in space and compared it with data from his identical twin brother – retired astronaut Mark – on Earth. The study gives an insight into the potential risks of a long-term mission to Mars.
Although they are not yet definitive, NASA has just revealed the first few results of the tests that Scott has undergone so far. Data analysed includes immune response, bone formation, gut microbiome, and how DNA might be affected by living beyond the Earth's atmosphere.
— Scott Kelly (@StationCDRKelly) January 28, 2017
One of the most surprising findings for researchers was that Scott's telomeres – the repetitive sequences at the end of a chromosome – increased in length while he was in space. They shortened again when he returned to Earth. Telomeres decrease in length as someone gets older, and it was thought that in space this process would accelerate, but the opposite occurred.
Researchers believe the change could be linked to an increase in exercise and a decrease in calorie intake while on the station, but they are intending to study it in more detail. John Charles, NASA Human Research Program chief scientist, said: 'It's important to appreciate that telomere lengthening is not always a good thing, as telomere lengthening is also associated with some disease processes and pathologies. That is not the case in this instance, however.'
Unexpectedly, Scott's telomeres, which are usually shortened by aging, lengthened
Another mystery is whether or not there is a so-called 'space gene'. By sequencing the RNA in the twins' white blood cells, researchers found over 200,000 RNA molecules that were expressed differently between the twins. It's normal for twins to have unique mutations in their genome, but researchers are 'looking closely to see if a "space gene" could have been activated while Scott was in space,' according to NASA.
Upon landing, Scott found that he had considerably more severe muscle and joint pains than he had suffered after his previous mission, which had lasted just six months. However, after putting Scott through motor tests, such as climbing stairs, navigating obstacles and using tools, scientists did not detect any anomalous differences with astronauts who had spent less time in space.
Although the tests revealed a decrease in bone formation, there was an increase in the levels of a hormone responsible for repairing muscle and bone. The reason for this increase seems to be the constant physical exercise required to prevent flaccidity. Having no weight due to lack of gravity, astronauts stop using their muscles and these end up shrinking. Bones can lose up to 12% of their density.
Having no weight, muscles are not used and end up shrinking
One thing that Scott lost was accuracy and reaction time when using a computer screen, as revealed by tests monitoring whether he could drag items, key in text or adjust shapes on the device. This information could be important for a potential future mission to Mars because astronauts depend on technology to survive in a hostile environment.
Living in microgravity also generates transient effects such as a swollen face (without gravity, blood and body fluids travel more easily through our body, and this can be seen in the physiognomy of the body and face) or changes in height. Scott is now 5 centimetres shorter than when he first landed. He grew in space because microgravity stretched his spine.
Another, more worrying, observation is that Scott's level of methylation decreased. DNA methylation is essential for normal development and is associated with a number of key processes, including aging and carcinogenesis. In Scott, this level decreased during flight, while increasing in Mark halfway through the study. 'These results could indicate genes that are more sensitive to a changing environment, whether on Earth or in space,' said NASA.
The twins also had different gut bacteria – the 'bugs' that aid digestion. NASA suggests that this was most likely a result of their different diets and environments during the year-long study.
The effects on Scott of his time in space will continue to be studied. Researchers hope that future results will shed more light on the question of whether humans are biologically prepared to colonise Mars.