NASA Twin Study new results: Mark and Scott Kelly

NASA astronauts Scott and Mark KellyNASA

When NASA astronaut Scott Kelly stood up last March after
spending a year in space, he was two inches taller.

Kelly is part of a study NASA is conducting to assess how the
human body changes as a result of space travel, using Scott Kelly
and his twin brother Mark Kelly as subjects. While Scott
spent 340 days aboard the International Space Station, Mark
stayed on Earth, giving NASA the rare opportunity to
compare two identical sets of DNA
— one that has been exposed
to the stressors of space, and one that has not.

Temporary additions in height
are just one of many
alterations the researchers have documented so far. Scott
and Mark have the same genes, but Scott’s year in space appears
to have strongly affected the way those genes are expressed.

“We can observe the entire human biological system
responding to space flight,” Christopher
, a principal investigator on the NASA Twins study and
an associate professor at Weill Cornell Medical College, told
Business Insider.

Researchers already knew that taking our bodies for a jaunt
outside Earth’s protective atmosphere has plenty of effects
on the human body, like
stretching your spine, shrinking your muscles, and messing up
your sleep cycle
— but the
effects of long-term exposure to space
have been less

NASA astronaut Scott Kelly
Kelly aboard the ISS.


The results of the twin study, though preliminary, are already
giving scientists a ton to think about.

Mason said they’ve seen “thousands and thousands of genes
change how they are turned on and turned off,” almost
immediately once an astronaut reaches space. Some
of these changes stick around for days or even weeks
after astronauts return to Earth.

The new findings about gene expression build on some preliminary
results that NASA released in February. Researchers hope to use
the full set of data, which could take some time to comb through
completely, to better prepare for future deep-space missions.

Here are some of the most interesting results so far:

  • Scott’s telomeres got longer, then shrunk back to
    Scott’s telomeres, or the caps at the end of
    chromosomes, became longer than his brother’s while he was in
    space, but quickly returned to their normal length once he
    returned home.”That is exactly the opposite of what we
    thought,” Susan Bailey, a radiation biologist at Colorado State
    University in Fort Collins,
    told Nature in Februrary
    . That’s because shorter telomeres
    are generally associated with getting older. Scientists are
    still studying what this means, but it could be linked to more
    exercise and eating fewer calories while in space, according to
  • Scott’s genetic expression changed in a bunch
    of ways.
    Scott’s genes showed both increased
    and decreased levels of methylation, a process that results in
    genes getting turned on and off. “Some of the most exciting
    things that we’ve seen from looking at gene expression in space
    is that we really see an explosion, like fireworks taking off,
    as soon as the human body gets into space,” Mason said
    in a recent statement.

    According to NASA
    , this could “indicate genes that are more
    sensitive to a changing environment whether on Earth or in
  • The twins hosted different gut
     Researchers noted differences between
    Scott’s and Mark’s gut bacteria (essentially the microbes
    that aid in digestion) throughout the year-long study. This was
    probably a result of their different diets and environments,
    NASA said.
  • Scientists are looking for what they’re calling a
    “space gene.”
    By sequencing the RNA in the twins’
    white blood cells, researchers found more than 200,000 RNA
    molecules that were expressed differently between the brothers.
    It is normal for twins to have unique mutations in their
    genome, but scientists are “looking closer to see if a ‘space
    gene’ could have been activated while Scott was in space,” NASA

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