02/04/2025
Imagine having a twin, someone with the same DNA, the same physical traits, and the same childhood experiences. Now, picture one of you staying on Earth while the other embarks on a year-long journey in space, orbiting the planet at 28,000 km/h, exposed to cosmic radiation and weightlessness. When you reunite, will you still be the same?
This isn't science fiction, itâs NASAâs Twins Study, a historic experiment that used identical twin astronauts, Scott and Mark Kelly, to uncover the effects of long-term space travel on the human body. While Scott spent 340 days aboard the International Space Station, Mark remained on Earth, serving as a living control sample. What scientists discovered could change the future of space exploration, including humanityâs dream of reaching Mars.
When Scott Kelly returned to Earth after nearly a year in space, scientists found something astonishing,his body had changed at the genetic level. While his actual DNA sequence remained the same, the way his genes expressed themselves had shifted. This process, called epigenetic change, is like flipping genetic switches on and off, altering how the body functions.
One of the biggest surprises was telomere lengthening. Telomeres, the protective caps at the end of DNA strands, usually shorten with age. However, in space, Scottâs telomeres became longer, possibly due to reduced stress and increased physical activity. But once he returned, they shrank back to normal, raising new questions about how space travel affects aging.
Additionally, around 7% of Scottâs genes remained permanently altered even after he returned. These changes involved genes related to the immune system, DNA repair, bone formation, and oxygen regulation, giving scientists new insight into how the human body adapts or struggles in space.
These mutations and genetic shifts are more than just fascinatingâthey are crucial for the future of space travel. If humans are to embark on deep-space missions, such as traveling to Mars, we need to understand the risks of long-term exposure to radiation, microgravity, and the psychological effects of isolation. The Kelly twins provided scientists with a unique opportunity to study these effects in real time.
Credit: Zakah Nur.
