Commander Scott Kelly of NASA. (Joel Kowsky/NASA)

Scott Kelly may be back on Earth (and back to his normal height) but his work as a guinea pig is just getting started. Kelly's record-breaking, year-long mission to the International Space Station is giving scientists across the country a treasure trove of valuable data to study, and NASA representatives say it could take two years for most of the related research to make it to the public.

In fact, Scott Kelly and his twin brother, Mark — who is being used as a sort of "control" for 10 experiments carried out over the course of the 342-day mission — will continue to report for NASA checkups and blood draws for another nine months. There are even samples taken aboard the ISS that won't return until May, when a SpaceX resupply vehicle equipped with a freezer comes back to Earth.

"Just because the flight's over doesn’t mean the mission’s over," NASA scientist John Charles said Friday during a news briefing. "The data analysis is only now beginning in earnest."

Much of the data will be batch analyzed — examined by the same technician, at the same time and place, with the same equipment — in an effort to avoid variables that may be mistaken for changes that occurred in space.

NASA likes to give researchers "a solid year" to work with the data they're given, Charles explained, and then those findings will be submitted to scientific journals for peer review — a process in which uninvolved experts check the studies to see whether they seem sound.

Initial results that provide insights may be published a year from now, Charles said, but it's likely that most findings will come out a year after that.

So for now, we only have anecdotal feedback on Kelly's record-breaking jaunt into space: During the Friday news briefing, Scott and Mark Kelly both mentioned Scott's eye trouble — a common problem for astronauts. When asked how the year-long mission had compared with his previous six-month mission, Scott Kelly said that soreness was an issue.

"Initially, this time, coming out of the capsule I felt better than I did last time," Kelly said. "But at some point those two lines have crossed, and my level of muscle soreness and fatigue is a lot higher than last time."

Kelly explained that some astronauts find the transition into life in space more tiring, and feel sick for awhile. He doesn't have that problem, but he does find the transition back to normal gravity to be difficult. But he added that he thought he could have gotten himself out of the Soyuz without help, had it landed upright — which is important, because astronauts landing on Mars after six months of space travel will need to stand on their own two feet. But the gravity there isn't quite as strong.

Kelly also mentioned a burning sensation in his skin that he hadn't experienced before.

"Because it hadn’t touched anything in so long it’s very very sensitive, it’s actually a burning feeling," he said. It's been nearly a year since his feet regularly touched the ground or he sat down in a chair with the full weight of gravity pushing him into it, so he's slowly adjusting to having regular contact with surfaces again.

In addition to cellular, genetic and physiological studies, some of the researchers will focus on Kelly's psychological well-being. Kelly said repeatedly that he had felt good during the mission. But he still missed Earth.

"I think the only big surprise was how long a year is," Kelly said. "It seemed like I had lived there forever."

Kelly is hopeful that we'll make it to Mars — but he seemed confident during Friday's briefing that his time flying with NASA is over.

He said he would miss the sense of accomplishment and fulfillment he got from working in such a risky environment — one with such high stakes.

"If I never fly in space again, I’ll find that in other areas of my life. . . but never in this way," he said.

And he expressed an interest in piloting a private spacecraft. "They might need a guy like me someday," he said, adding that he might even consider buying a ticket if recreational space travel opens up to the public.

Throughout the briefing, Kelly remained humble about his records — for the longest single spaceflight ever undertaken by an American and for the most total days in space ever held by the same.

"These records are made to be broken," he said, pointing out that some astronauts already have flights scheduled that will shatter his total day record.

And when asked how he felt about his sudden fame, he seemed surprised, saying he wasn't aware he had had such an impact on the public.

"Where've you been?" a reporter joked.

"I've been watching the presidential primaries," Kelly deadpanned.

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