Columbus, Ohio --

NASA surprised John Glenn with the kind of anniversary gift only a space agency can give, enabling him to speak live with the International Space Station on Monday as he marked 50 years since his historic spaceflight.

The former astronaut and senator from Ohio, now 90, became the first American to orbit the Earth on Feb. 20, 1962, circling it three times in five hours and helping to lead the nation into space. He celebrated the anniversary at Ohio State University by kicking off a forum about NASA's future.

Sitting on stage with NASA Administrator Charles Bolden, he chatted with three space station crew members about space research and NASA's future. Commander Dan Burbank appeared by video link, flanked by two flight engineers floating in the zero-gravity environment, and said the crew was delighted to help commemorate Glenn's momentous trip.

Glenn was among the top military test pilots presented in 1959 as the Mercury Seven. The only other surviving Mercury astronaut is Scott Carpenter, who called out the memorable line "Godspeed John Glenn" moments before the rocket ignited for Glenn's spaceflight.

"Fifty years ago today, Friendship 7 was orbiting planet Earth, and that helped in a very big way, paved the way for America to become a space power, and to go to the moon, and to do the things that we're doing right now on the International Space Station," Burbank said. "And we hope this also can help set the stage for us down the road to do even greater things."

Glenn had a light-hearted but educational exchange with the space station crew, asking them about the types and number of experiments on board - more than a hundred, they said - and explaining to his gravity-bound audience of more than 200 people that, for example, a candle burns differently in space than on Earth.

When Bolden asked the astronauts which experiment they'd like to hand off to Glenn if he could join them, Burbank suggested research on the "regenerative environmental control systems" on spacecraft.

"That's a fancy word for our toilet," flight engineer Don Pettit added. "So he wants to put Sen. Glenn busy fixing the plumbing up here."

Glenn took the humor in stride, replying: "That's exactly what I thought I was going to get assigned to."

Glenn also inquired about how far the space station had traveled during the course of the roughly 15 minutes they'd been talking. They hadn't kept an eye on the exact distance but said they guessed it was about one-fourth of the way around the Earth.

Bolden joked that Glenn sometimes bugs him about making a trip to the space station. Glenn became the oldest person to fly in space in 1998, at age 77.

Astronaut Neil Armstrong, the first man to set foot on the moon, was the surprise speaker Monday evening at a gala honoring Glenn.