Follow Scott Kelly’s giant step for mankind

Even an old astronaut like me can still marvel at the power of President Kennedy’s declaration more than a half-century ago that space was the “new ocean” — and one we must “sail on.”

For more than 50 years, we have explored those dangerous and unknown waters to become a leader in space: Mercury, Gemini, Apollo, Skylab, the space shuttle, the Hubble Space Telescope, the Mars rovers and the International Space Station — an orbiting base occupied for the past 15 years by an international crew.

Now we have another American achievement and milestone: One of our countrymen has spent nearly a year off of our planet. Astronaut Scott Kelly has orbited Earth more than 5,000 times, traveling well over 100 million miles aboard the International Space Station. Scott has made an incredible sacrifice for our country as he has lived cut off from his family and friends and risked his life in the name of space medical science. He is building a foundation for the next chapter of American space flight.

There is a simple truth about space flight: The more time you spend in space, the more likely you are to die in it. Though we have lost American astronauts only at launch or re-entry, it’s also risky living in space as Scott has done for a year of his life.

The risks are many: the huge dosage of cancer-causing radiation you take on without the protection of the atmosphere; the constant threat of ammonia leaks; a catastrophic fire or loss of air due to impact with space debris. Given these risks, why fly in space for a year?

Scott has flown so long so we can make huge advancements in our understanding of how longduration space flight impacts human physiology, something that is essential if we are ever going to travel to more distant destinations, such as Mars. Because Scott happens to have an identical twin brother — a fellow retired astronaut and my friend, Capt. Mark Kelly — NASA researchers are using Mark as a control subject on Earth while Scott serves as the test subject 250 miles above us.

One day, an American will walk on Mars. But we will get there only because we chose to do it and because our leaders in Washington decided it was important.

Scott’s voyage is not over. He still faces a return to our planet on Tuesday, when he and his Russian crew mates will climb into a Russian Soyuz capsule, undock from the space station, re-enter our atmosphere and, God willing, land safely in the semi-arid steppes of Kazakhstan.

And on Wednesday, when Scott arrives at Houston’s Ellington Field, his loved ones will undoubtedly be there to embrace him. But I hope our nation embraces Scott, too, and honors the bravery, service and sacrifice embodied in his year in space.

It is a remarkable achievement, one worthy of our gratitude, and one that paves the way for the next generation of American space missions and American voyagers who dare to sail the vast, dangerous and beautiful ocean of space.