Who are Scott and Mark Kelly, and what was NASA's Twins Study on the astronauts?

Scott Kelly and Mark Kelly are American astronauts and identical twin brothers. They participated in NASA's Twins Study, conducted between 2015 and 2018.

Updated on: Mar 19, 2025, 06:02:19 IST

By HT News Desk

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Scott Kelly appeared on Fox News with anchor Bret Baier to discuss the return of NASA astronauts Butch Wilmore and Sunita Williams from the International Space Station (ISS). Kelly, a former NASA astronaut, is the identical twin brother of Mark Kelly, also a NASA astronaut and a Democratic senator from Arizona.

Scott Kelly and Mark Kelly are American astronauts and identical twin brothers. (X/Mark Kelly and Facebook/Scott Kelly)

Who is Scott Kelly?

Scott Kelly is a former military fighter pilot, test pilot, engineer, retired astronaut, and US Navy captain. According to his official website, Scott Kelly has completed four space flights and commanded the International Space Station (ISS) during three expeditions. He was also a member of the yearlong mission aboard the ISS. In October 2015, Scott set a record for the most cumulative days spent in space, completing the longest single space mission by an American astronaut. Kelly now resides in Houston, Texas.

Who is Mark Kelly?

Mark Kelly is a retired astronaut, United States Navy captain, and the senior United States senator from Arizona, a position he has held since 2020.

Last week, Mark Kelly shared in a video message that he is parting ways with his Tesla, citing that when he purchased the vehicle, he did not anticipate it becoming "a political issue."

Kelly expressed his discontent with President Donald Trump and the Department of Government Efficiency (DOGE) led by Elon Musk, stating that he now finds it difficult to continue driving the car.

“So this is going to be my last trip in this car. There's some things I really like about it, there are things I didn't like about it. But that doesn't matter. What matters is you know doing the right thing. I think it's time to get rid of it. Elon Musk kind of turned out to be an a******. And, I don't want to be driving a car built and designed by an a******. So, looking forward to my new ride,” he said.

NASA's Twins Study -

The Kelly brothers participated in NASA's Twins Study, conducted between 2015 and 2018, which examined the effects of long-duration spaceflight on the human body. While Scott spent 340 days in space, Mark remained on Earth as a control subject. Scientists compared the twins before, during, and after Scott's mission to better understand how the space environment impacts the body at molecular, physiological, and psychological levels.

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HT News Desk
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