NASA has been increasing its efforts to develop new technologies that would bring humans back to the Moon’s surface by 2024. The mission would mark the beginning of humanity’s deep space exploration, with a target to reach Mars over the next decade. 

The U.S. government wants to send astronauts to the Red Planet in 2033. But are we ready for the mission? Despite the rapid development of technologies to take humans into space, little is known of how a long-term mission outside of Earth could affect the human body. 

That is the issue raised by a new NASA study recently published in the journal Science. It provides new information on what happens to the human body after a year in space.

The study was conducted by astronaut Scott Kelly, who worked on the International Space Station from March 2015 to March 2016 and his twin brother, Mark, also an astronaut, who stayed on Earth, according to Wired.

The two astronauts were separated for a year to see how a long space flight affects the body. Scott and Mark submitted samples, including stool, urine and blood and took cognitive and physical tests before, during and after the mission. 

Results of “The NASA Twins Study: A Multidimensional Analysis of a Year-Long Human Spaceflight” suggested that living outside Earth could affect genetic, immune system and metabolic functions and cause disrupted circadian rhythms or sleep cycle. 

Chris Mason, the principal investigator of the Gene Expression Group and a professor of physiology and biophysics at Weill Cornell Medicine, said the impact of space travel on Scott’s genes “was like fireworks in the sky.” 

Mason’s team found more than 10,000 genes were activated by spaceflight. Other changes that occurred in Scott’s body included his gene regulation, the bacteria in his gut, the dimensions of his carotid artery and the health of his eyes.

Many of his immune-related cellular pathways were also disrupted, including the ones that protect the body from cancers. Scott’s cognitive function decline during his stay on the ISS. Researchers said he got dumber during the mission. 

Luckily, the astronaut returned to normal within six months of coming back to Earth. However, some impacts of his long space flight remained, including the decline in the speed and accuracy of his mental functions.

The changes in Scott’s body increased his risk of having heart disease, cancer and heritable diseases, according to the study. 

The ISS is only 250 miles above Earth and the astronaut only stayed in space for a year. The mission to Mars is expected to take longer due to its distance, which may pose more risks to astronauts. 

Researchers plan to conduct more studies to determine how to address such space flight concerns.