How NASA Used Twins To Pave The Way For Long Term Space Travel

Twins are pretty rare, only about three percent of children are twins, identical twins are even less common accounting for just 0.45%, roughly one in every 250 births. Suffice to say getting identical twins who both end up as astronauts is a bit of a rarity! So, of course, NASA was going to take advantage.

The astronauts

The twins are Scott and Mark Kelly. Although twins often follow similar paths these guys were pretty much inseparable. They joined the Navy together, both have the same amount of children and even went through cancer at the same time! However, that is all typical twin coincidences.

The experiment

Nasa wanted to get a true reflection of the effects on the human body of lengthy periods in space. What better way to test that on two people who are genetically identical (or at least 99.9%!) The idea was to look at the effects of being in space at a molecular level. Something that had never really been done before it was the idea of Scott himself.

Various samples were taken as Scott was in space and his brother Mark remained on earth. These included blood, urine, etc. Of course, the stakes were incredibly high given the unique situation. As we pointed out it isn’t every day you happen across identical twin astronauts! So it was of great importance that the lab workers were on their game, which fortunately they were.

We can survive

Obviously, we have had people spend prolonged periods of time in space now. And there have been a wealth of studies on the physical effects on people who do this. However one of the biggest finds from this experiment is the fact that our bodies cope just fine on a cellular level. This is great news for any future endeavours.


One of the big discoveries made was the effect on telomeres. Now brace yourself because things are about to get just a tad technical. Telomeres, put very crudely, are the caps that are on the end of chromosomes. They effectively stop the chromosomes from getting damaged. The tests showed that two days after his flight his telomeres had stretched and after returning to earth they returned to their normal size.

Gene expression

Another thing that the team noticed where the changes in gene expression. What is gene expression? Well, there are various genes in your body that can be “switched on or off” these control countless bodily functions and genetic expression happens to everyone, every day. However, due to the stresses of space flight, there was an increase in activity in Scott’s genetic expression as the science team would have predicted, however after six months of returning almost 90% of this had reversed itself.

Space travel is tough

If you hadn’t guess it can be tough being an astronaut. The effects of zero gravity can take their toll on your body. Because on earth our bodily fluids are affected by gravity and in space, they are not astronauts regularly have more fluid in their head then they should, consequently almost half of them end up with vision problems as a result.

How this is useful

Obviously, an isolated experiment provides some data but doesn’t give us anything concrete to work with. Looking to the future with talks of further trips to the moon and the mooted colonisation of Mars the health of astronauts is going to be a big consideration. Over the next few years, experiments like this can be done on astronauts spending time at the international space station. And this experiment helps us know what sort of things we are looking for. It gives us goals to try and repeat so we have a far greater understanding of the effects of space travel on humankind.

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