Two crewmembers onboard the International Space Station have been in space for six months, reaching the halfway milestone of a planned one-year stay in space.
American astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko are set to spend a full year in orbit to help scientists better understand what humans might face on the long journey to Mars, and how the human body might react and adapt to extended spaceflight.
A trip to Mars, using any existing propulsion technology or near-future possibilities, would take more than a year each way.
"I think the legacy of this mission will be based on the science of having us in space for a year," Kelly said in a recent interview conducted from aboard the ISS. "The great data we collected, what we learned about being in space for this long and how that will help our journey to Mars someday."
Research involving American and Russian crewmembers on the ISS is shared between the two countries, NASA explains, to reduce costs and to improve the efficiency of research aboard the space stations.
An additional opportunity to study the effects of long-term spaceflight is provided by the fact that Scott Kelly has a twin, retired NASA astronaut Mark Kelly, who is providing researchers with data for a comparative genetic study to gauge differences that might develop between the Earth-bound twin and his orbiting sibling.
Scott Kelly says he's decided to take life aboard the ISS at a slower pace compared with that of his last orbit there, when he spent 159 days in the orbiting laboratory.
"I intentionally thought about ways for me to get to the end of this with as much energy as I had in the beginning," Kelly said in an interview carried on NASA TV. "I intentionally don't work at the same pace I did last time I was up here, when I felt like I could go at 100 percent speed for the full six months."
Most missions to the ISS see astronauts and cosmonauts spend a maximum six months in orbit.
Even with the long stay, astronauts on the ISS have it somewhat easier than people on a Mars mission would.
They can see the Earth and communicate easily with people below, and, unlike Mars missions where the same group of people would be confined in a small space for a very long time, crewmates on the ISS change from time to time, allowing for some variety and change in personalities.
Still, Kelly says, a long mission on the ISS is not walk in the park — and in fact, the chance to take a walk is something he misses.
"This is a very closed environment. We can never leave. The lighting's always pretty much the same — the smells, the sounds, everything's the same," Kelly said. "I think even most prisoners can get outside occasionally in a week. But we can't. And that's what I miss, after people."
