Space travel can do funky things to the human body. Its possible for astronauts to return to Earth slightly taller, with smaller muscles, more fragile bones, and the worst hangover ever.

When the American astronaut Scott Kelly returned to Earth, Nasa scientists had a unique opportunity: the ability to look at how space travel influences a persons DNA.

Scott Kelly is a twin. Between 2015 and 2016 he spent 340 days in space, making the International Space Station his home. Before, during, and after his trip, Scott gave blood samples for researchers to examine. Back on Earth, Scotts twin brother and retired astronaut, Mark Kelly, was also giving blood samples to researchers.

Since Scott and Mark are twins, they share the same DNA. They are part of the aptly named Nasa Twin Study, in which 10 research labs from 12 US universities compare the changes to space traveller Scotts DNA versus those of Mark to see if there are differences in Scotts DNA which they could attribute to space travel.

One year later, the researchers are beginning to publish their early results.

Almost everyone is reporting that we see differences, states Christopher Mason, a geneticist from Weill Cornell Medicine and a researcher involved in the study.

Differences were expected. But many of the differences the researchers are finding are simply surprising.

One of the biggest surprises was the lengthening of Scotts telomeres while he was in space.

Telomeres are biological markers located at the end of DNA. Associated with health, age, and longevity, telomeres naturally shorten as a person ages.

According to Susan Bailey, another researcher involved in the study, [this] is exactly the opposite of what we thought. The common belief was that space travel would shorten the telomeres because of cosmic radiation and other dangers associated with space travel. But, curiously, once Scott returned to Earth his telomeres shortened to their normal length.

Some scientists speculate that the lengthening of Scotts telomeres is associated with exercise and a specialised space diet. However, this theory has not garnered consensus, and Nasa is now undergoing a one-year study looking at changes to the telomeres of astronauts.

Another surprise was the presence of 20,000 unique variations of mRNA in Scotts during space blood sample.

mRNA is a type of molecule produced directly from DNA. Different genes in the DNA can produce different mRNA, and mutations to DNA produce variations of the same mRNA molecules. However, the large number of mRNA variations seen in Scotts blood samples indicate the possibility of a space gene, which only produces these mRNA variants when the person is in space.

Other noted differences included different composition of gut bacteria and a decrease in DNA methylation, a biological marker which indicates the activity of a gene.

However, the researchers are careful to qualify which differences are due to space travel and which are due to the natural variation of DNA that occurs because of different overall life experience.

The information from the Nasa Twin Study marks the beginning of looking at space travel effects from a nature versus nurture standpoint.

Nasa plans to use this information to produce personalised medicine and diet during long term missions and further examine the stresses of long term space travel.

Image: Alanah Knibb

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Twins in space: intergalactic travel could change DNA - The Student