Astronaut Scott Kelly, re-adapting to gravity, people and wide open spaces after a record 340 days cooped up aboard the International Space Station, said Friday his muscles and joints are a bit sore -- "just about all of 'em" -- his skin is surprisingly sensitive and "I never felt completely normal up there."
Even so, Kelly told reporters at the Johnson Space Center that overall, he feels good and that if he had just landed on Mars after a long trip from Earth, he would have been able to do useful work.
Kelly and cosmonaut Mikhail Kornienko were launched to the space station last March 27. They returned to Earth, along with Soyuz TMA-18M commander Sergey Volkov, late Tuesday U.S. time, landing on the steppe of Kazakhstan to close out their record mission.
Kelly and Kornienko both appeared remarkably fit after they were pulled from the cramped Soyuz descent module, smiling and chatting with support crews in obvious good spirits. Arriving back in Houston Wednesday night, Kelly said he was glad to be home after "a very long trip."
"When I left here, I was 50. And now I'm 52," he joked. "But it feels great, it's great to be back in Texas on U.S. soil. It's just an unbelievable feeling to be back here on planet Earth, back in our great country and back with all my family and my friends."
After going home that night, he enjoyed dinner with family and friends and later, walked outside and fell into his swimming pool, fully clothed, posting the video on Twitter. Coming up to the surface, he exclaimed "oh man, that feels good!"
"The reason I was eager to jump in the pool was because even though I took a shower in Canada (on the way home from Kazakhstan) I hadn't had running water in 340 days," he said. "It's something you really miss. ... We make do with not having a shower on board, and it's not like you feel dirty, but you definitely feel like you would like to jump in a pool. So I did."
Kelly flew aboard the station for 159 days in 2010-11 and said he initially felt better after landing this time around than he did the last.
"You know, there's always a certain amount of soreness and fatigue and that kind of stuff," he said. "Initially, this time, coming out of the capsule, I felt better than I did last time. But at some point, those two lines have crossed and my level of muscle soreness and fatigue is a lot higher than it was last time.
"I also have an issue with my skin," he added. "Because it hadn't touched anything for so long, had any significant contact, it's very, very sensitive. It's almost like a burning feeling where I sit or lie or walk."
Problems re-adapting to gravity show up in virtually all aspects of day-to-day life, he said, and in his experience, it is easier to adapt to space than the other way around.
"The first thing I tried to throw on a table, I missed," he said. "I tried to shoot some basketballs yesterday, and I didn't get any of them in the net. Not that I'm a good basketball player in general anyway. I don't seem to have a tendency, though, to want to drop things like some people.
"But definitely, throwing things, you tend to underestimate the effects of gravity. What's really harder, though, is throwing something in space straight. You always wind up lofting everything."
Asked if he had experienced any sort of "culture shock" returning to Earth after nearly a year in space, Kelly said his previous spaceflight experience had prepared him for the sudden presence, or "shock," of "all the people there when you've seen so few people for so long."
"I've been very busy since I got back, so I don't think it's really hit me yet," he said. "I think there'll be a point here pretty soon where I'll start maybe feeling that kind of culture shock, or whatever else you would want to call that, from having ... so few choices about what you're going to do every day, what's available to you, to basically having just about anything."
Kelly and Kornienko, along with Scott's twin brother Mark, a former shuttle commander, are the subjects of wide-ranging research to learn more about the long-term effects of weightlessness and space radiation. The goal is to help engineers and scientists develop the countermeasures necessary to eventually send astronauts on long-duration trips to Mars and beyond.
Data collection began before launch, continued throughout the flight aboard the space station and will go on for months to come as researchers measure how Kelly and Kornienko re-adapt to gravity. Mark Kelly is participating in research that will look at genetic changes that might have occurred because of Scott's long flight in the space environment.
"We're really trying to understand what the advantages are of doing this kind of work and what better way to do it than to compare two individuals who, at least at birth, were fairly identical genetically," said John Charles, associate manager of NASA's Human Research Program.
"So by looking at Mark's results collected over the course of the year, we can see what the normal variations might be and then by looking at Scott's, we can see where his variations are greater than Mark's. And those will tell us what areas to investigate in the future."
But Charles aid it will take many months to analyze all the data from the nearly yearlong mission, including samples still aboard the space station that will not get back to Earth until later this year. For the Kelly twins, that translates into many more months serving as test subjects.
"We have plans for data collection on both Scott and Mark up to nine months after this landing, and that's just data collection, not even including the analysis time," Charles said. "Just because the flight's over doesn't mean the mission's over. We've got lots of other investigations, lots of other little surprises to spring on Scott and Mark as we continue on in this process."
On top of that, NASA typically gives researchers a full year to complete their analysis and publish the results.
"So this time next year, I'm hopeful we'll start seeing initial results come out from the investigations that were fairly quickly completed and fairly quickly analyzed, and then I look for a constant stream of insights and results from this mission for at least another year after that."
While a record-setting mission for NASA, Kelly's flight still falls far short of records set by Russian cosmonauts in the days of the Mir space station. Vladimir Titov and Musa Manarov each logged 366 days aloft while Sergei Avdeyev spent 380 days in orbit and Valery Polyakov logged 438 days.
But state-of-the-art medical technology and procedures are expected to generate an enormous amount of top-quality data on Kelly and Kornienko, data scientists say is critical for developing the countermeasures needed for an eventual flight to Mars.