Nasa twins reveal humans' space resilience

Washington DC: NASA's landmark twins study has revealed surprising and reassuring data about how one human body adapted to -- and recovered from -- the extreme environment of space, the US space agency said.

The Twins Study, which took place from 2015-2016, provides the first integrated biomolecular view into how the human body responds to the spaceflight environment.

It serves as a genomic stepping stone to better understand how to maintain crew health during human expeditions to the Moon and Mars, NASA said in a statement.

Retired NASA astronauts Scott Kelly and his identical twin brother Mark, participated in the investigation, conducted by NASA's Human Research Program and encompasses work from 10 research teams.

Mark provided a baseline for observation on Earth, and Scott provided a comparable test case during the 340 days he spent in space aboard the International Space Station (ISS).

Scott became the first American astronaut to spend nearly a year in space.

"The Twins Study has been an important step towards understanding epigenetics and gene expression in human spaceflight," said J D Polk, chief Health and Medical Officer at NASA Headquarters.

"Thanks to the twin brothers and a cadre of investigators who worked tirelessly together, the valuable data gathered from the Twins Study has helped inform the need for personalised medicine and its role in keeping astronauts healthy during deep space exploration, as NASA goes forward to the Moon and journeys onward to Mars," Polk said in a statement.

Key results from the NASA Twins Study, published in the journal Science, include findings related to gene expression changes, immune system response, and telomere dynamics. Other changes noted include broken chromosomes rearranging themselves in chromosomal inversions, and a change in cognitive function.

Many of the findings are consistent with data collected in previous studies, and other research in progress, NASA said. The telomeres in Scott's white blood cells, which are biomarkers of ageing at the end of chromosomes, were unexpectedly longer in space then shorter after his return to Earth with average telomere length returning to normal six months later.

In contrast, his brother's telomeres remained stable throughout the entire period, the study found.

A second key finding is that Scott's immune system responded appropriately in space.

For example, the flu vaccine administered in space worked exactly as it does on Earth, the US space agency said.

A fully functioning immune system during long-duration space missions is critical to protecting astronaut health from opportunistic microbes in the spacecraft environment.

A third significant finding, NASA said, is the variability in gene expression, which reflects how a body reacts to its environment and will help inform how gene expression is related to health risks associated with spaceflight.

While in space, researchers observed changes in the expression of Scott's genes, with the majority returning to normal after six months on Earth.

However, a small percentage of genes related to the immune system and DNA repair did not return to baseline after his return to Earth.

The study identified key genes to target for use in monitoring the health of future astronauts and potentially developing personalised countermeasures.