HARI SREENIVASAN: It's a dream many have had, traveling into space, and then even living
there for some period of time.
Just a small group of people on the planet have done it.
That includes American astronaut Scott Kelly.
Naturally, our Miles O'Brien had lots of questions about what happens to the human body, and
to the person, once back on Earth.
It's part of our weekly series about the Leading Edge of science.
MILES O'BRIEN: A year in space is not for the faint of heart.
Scott Kelly found that out aboard the International Space Station from March 2015 until March
2016.
Now that he is firmly anchored on terra firma, he's out with a memoir, "Endurance," and a
sequel to the PBS film "A Year in Space," aptly titled "Beyond a Year in Space."
Both book and film detail his slow, dizzy, painful return to the pull of gravity.
Did you get the sense that you were hurting yourself?
SCOTT KELLY, NASA Astronaut: So, at times, yes, especially when I got back, and I didn't
feel great, and your body is reacting to gravity, something I think all astronauts are aware
of.
There's risk involved from being in space for long periods of time.
MILES O'BRIEN: Astronauts returning from long-duration spaceflights routinely complain of being achy,
confused and delirious, flu-like symptoms.
Their feet are tender from lack of use, and, for the same reason, their bones are weaker
too.
Two astronauts who spent long stints on the station broke their hips not long after landing.
And for reasons not fully understood, their vision is impacted too, for some permanently.
Right now, what's your vision like?
Is it the way it was?
Has it gotten worse?
SCOTT KELLY: It's back to where it was before I flew.
You know, in space, my vision is affected because I think of the fluid shift.
Your eyeball changes a little bit of shape when your head is more full of fluid.
I think the fluid shifts experiment, however, was to look at kind of long-term effects and
damage that occurs to the structures in our eyes.
MILES O'BRIEN: Did you really volunteer to have an implant put in your head to measure
this?
SCOTT KELLY: I actually did.
I pushed for it, but I also know how conservative NASA could be.
So...
MILES O'BRIEN: So, you knew they'd say no?
It was easy to volunteer on this one.
(LAUGHTER)
SCOTT KELLY: I would have done it.
I was a willing participant, but I knew the odds of them actually taking a drill to my
skull was pretty unlikely.
MILES O'BRIEN: NASA did take him up on another offer in the guinea pig category.
He and his twin brother, Mark, a former astronaut himself, agreed to be constantly tested before,
during and after the mission.
Their nearly identical genomes offered scientists a way to control studies on how space travel
affects the human body.
"Beyond a Year in Space" takes us inside his reunion with his brother and his fiancee,
Amiko Kauderer.
AMIKO KAUDERER, Fiancee of Scott Kelly: Welcome home, back to Earth.
SCOTT KELLY: Oh, that feels good.
You know, I have served the government for 30 years.
And I feel very strongly about space.
I think it's important.
I would never rule out flying in space again, but I think it's probably unlikely.
MILES O'BRIEN: And it gives us a glimpse into the non-glamorous side of these twin astronauts
as lab rats.
SCOTT KELLY: You know, we figured out I have spent 40 hours in that machine.
I have got to go do some science in the bathroom.
I will be right back.
They have more genetic information on my brother and I than they do of any other people, ever.
MAN: Yes, you're going to lose a couple pounds here.
MILES O'BRIEN: Our atmosphere and magnetic field protect us from the high levels of radiation
found in space.
So, exposure to radiation is one of the main concerns for astronauts headed to Mars.
In his book, Kelly writes about closing his eyes at night and seeing flashes from radioactive
ions.
You do take a healthy dose up of radiation when you are up there, don't you?
SCOTT KELLY: So, you know, it's something you think about, especially when you see those
flashes, and you realize, hey, that cosmic ray didn't just go through my eye.
It went through my brain.
MILES O'BRIEN: I forgot what you say.
It was several chest X-rays a day or something like that.
SCOTT KELLY: Yes, and, sometimes, you hear 20.
It varies.
I think it varies based on the solar max, solar min, the size of the atmosphere, the
magnetic field.
MILES O'BRIEN: A bombardment of radiation increases the chances human cells and DNA
will form abnormalities that can lead to cancer.
And Scott Kelly is already a cancer survivor.
As a cancer survivor, you know, you have got to think about them really long and hard.
Tell me how that played in.
SCOTT KELLY: I don't think it did.
You know, I kind of look at myself as a guy whose prostate had cancer, and then the prostate
was removed.
MILES O'BRIEN: And you have been cancer-free for how long now?
SCOTT KELLY: Almost 10 years now.
MILES O'BRIEN: Congratulations.
SCOTT KELLY: Thank you.
MILES O'BRIEN: The air aboard the station contains relatively high levels of carbon
dioxide.
The devices on the station that remove CO2 generated by human respiration are quirky,
hard to repair, and, as a result, NASA doesn't run them at full blast.
Is it uncomfortable to be up there for a long period of time because of this?
SCOTT KELLY: I could actually tell what the CO2 was just based on my symptoms.
I would actually get irritated.
Amiko, my fiancee, would even say to me, so, is the CO2 high today?
And I would say, yes, yes.
How'd you know?
And she said, well, I could tell by the way you sound.
MILES O'BRIEN: Designing a way for humans to not just survive, but thrive, on a mission
to Mars is what Kelly's mission was all about.
And it turns out the psychological rigors are among the most important to consider.
Do you walk away from this reasonably optimistic that human beings are well-adapted to do that
part of it, the psychological rigors?
SCOTT KELLY: I think some of them are, but I have flown in space with people that I don't
think should be someone that spends a really long time in space.
I think it's for a certain type of person.
There's hundreds of thousands of people in our country that have the endurance to do
a mission to Mars someday, absolutely.
MILES O'BRIEN: But you do miss home a lot, don't you?
SCOTT KELLY: You know, most everything is on Earth.
It's got a lot to offer.
MILES O'BRIEN: Would you go to Mars if you had a chance?
SCOTT KELLY: As long as I had the return ticket.
I wouldn't be one of these Mars One guys.
One-way is not for me.
MILES O'BRIEN: I'm with you on that.
(LAUGHTER)
MILES O'BRIEN: A new generation of astronauts are in the early stages of training for a
round-trip mission that would last at least 500 days.
They have already learned some key lessons of endurance from a spacefarer who's written
the book on it.
For the "PBS NewsHour," I'm Miles O'Brien in Boston.
HARI SREENIVASAN: And that special about Scott Kelly, "Beyond a Year in Space," airs tonight
on many PBS stations.