A groundbreaking study to examine astronaut’s DNA could prove to be a pilot study in NASA’s ultimate goal of sending humankind to Mars.

Data released in March 2017 shows astronaut Scott Kelly’s genome changed over the course of his near-year—340 days—in space.

Scott and his twin brother Mark are the only twins to ever travel to space, and they were selected to participate in the Twins Study, a close-up look at how human bodies change in microgravity environments.

Project scientists said the study is vital in being able to develop personalized, long-term health care for astronauts eventually traveling in deep space.

Preliminary data from the multi-faceted, international study shows Scott’s DNA actually changed while aboard the International Space Station. The protective coatings on the end of his DNA changed, elongating and puzzling project scientists. Telomere length can impact aging and age-related diseases.

As humans age, telomere loss is inevitable.

When the sequences run out, an individual is more susceptible to developing a disease.

Dr. Graham Scott, Chief Project Scientist at the National Biomedical Research Institute and Deputy Project Scientist for the Twins Study, equated telomeres to our biological clock.

“We want to understand as much as we can about the human body,” Scott said. “If you are losing bone or muscle mass, or something is going on with an astronaut’s eyesight, we have to see what’s happening at the molecular level so we could eventually develop counter measures for those types of problems.”

Astronauts headed for Mars and beyond will need to deal with range of health hazards including vision problems, muscle and bone mass loss, among other conditions. Scott showed more bone loss in the second-half of his roughly 12-month mission than the first half, and NASA will examine bone loss in astronauts more closely in the future.

Astronauts typically lose seven percent body mass while in space.

Currently, astronauts bone or muscle mass loss with strict regimens of exercise and nutrition while in space.

“Conditions for diseases show up at the molecular level,” Scott said. “The idea of doing molecular testing in space is that we could detect early signs of radiation damage. It could be an early detection system, and it could also depend on the biomarkers or specific molecules observed. It might give us a chance to employ a countermeasure before symptoms arise in a case where an astronaut might not even notice.”

Eventually, Scott said, scientists hope to parlay the data into conducting in situ molecular tests on astronauts.

The invasive study that drew a manner of samples from the twins will also help researchers better understand the ethical and legal implications of using genomic sequencing techniques on humans.

“When you do a genetic study about an astronaut, you’re not just revealing information about the astronaut. You’re revealing information about their entire family tree,” Scott said. “It’s a little different than doing a garden-variety study. That’s why the ethics of these studies has to be thought through.”

All U.S.-based research conducted aboard the ISS falls under the control of the Center for the Advancement of Science in Space in Florida. The center is tasked by NASA to administer all science operations sent to and from the space station.

The Twins Study consists of 10 individual investigations from 12 universities, CASS in Florida and the NSBRI. The project is a supplemental study built “on the framework” of Scott’s one year mission and subsequent investigations.

“On the non-scientific side, I think the team aspect of pulling these team investigators together is intriguing as well,” Scott said.  “That didn’t occur without considerable effort on the part of everyone involved. I think science is so integrated now, with people from diverse skill sets working together. You have engineers working with medical doctors who are in turn working with chemists or statisticians. I think it’s very common now.”

New data released showed an increase in methylation, the process of turning genes on and off, and additional knowledge in how that process works, according to an October 2017 NASA news release.

“Some of the most exciting things that we’ve seen from looking at gene expression in space is that we really see an explosion, like fireworks taking off, as soon as the human body gets into space,” Twins Study Principal Investigator Chris Mason, Ph.D., of Weill Cornell Medicine, said. “With this study, we’ve seen thousands and thousands of genes change how they are turned on and turned off. This happens as soon as an astronaut gets into space, and some of the activity persists temporarily upon return to Earth.”