United States Astronaut Scott Kelly has just beaten the record for the most cumulative days in space (for the US). As of today, he has a total of 383 days and counting, surpassing Mike Fincke, a two-time space station resident, who was the previous record holder at 382 days. This is not only a great achievement for himself and for astronauts in general, but it provides a great opportunity to study the effects of space travel on the human body – as Kelly has an identical twin back on Earth.

You see, out of all the important experiments carried out on the International Space Station, one is especially interesting: Kelly is using his own body as an experiment. NASA wants to compare his health to that of twin brother, retired astronaut Mark Kelly, who has remained on Earth. This will enable researchers to determine the effects that prolonged periods in space have on the human body – something especially important as NASA is preparing its mission to Mars, which will take over 150 days for one way.

The so-called “NASA twin experiment” will include 10 experiments in four areas: human physiology, behavioural health, microbiology and molecular. This is a rare chance, that two astronauts are twin brothers, with one of them staying for very long periods in space, and NASA wants to seize this opportunity.

‘This is a chance in a lifetime,’ said Dr Craig Kundrot, the deputy chief scientist of Nasa’s Human Research Program. ‘In this case we’ve got two genetically identical individuals and we can monitor what kind of changes occur in Mark in an ordinary lifestyle and compare those to the changes that we see in Scott.’ By staying on the station for 12 months, the astronauts will also provide key information on how an eventual Mars mission – estimated to last three years there and back – might play out.

As for Kelly, he’s enjoying his ride, but wants to see even more from his colleagues.

‘Records are meant to be broken. Look fwd to one of my colleagues surpassing my end 500+ days on our #JourneyToMars,’ Kelly tweeted today.

When he returns back to Earth, he will have spent a total of 522 days in space, an incredible figure! As he orbited above the Himalayas, he posted this dazzling picture of a sunset, filtered through solar panels on the ISS.

We here see only one sunrise and one sunset every day because the Earth is revolving around the Sun. But because the ISS revolves around the Earth, they get to see more sunsets – approximately one every 92 minutes.

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