The space shuttle Columbia carried explorers, dreamers. She carried the hopes not of a nation but of a world constantly bent on discovery.

She carried seven astronauts &045; men, women, white, black. She carried the first Israeli astronaut and an experienced Indian astronaut, both heroes to their home countries.

In the sky over Texas on Saturday, they were lost in a cloud of smoke and debris, but their work will live on.

Saturday morning’s tragedy was not, unfortunately, unthinkable. We have been in this place before, wondering what could have happened to one of the flying machines built by American ingenuity, by the diligence of the human spirit.

We grieve for the families of the astronauts killed, and for the NASA family that has worked so hard over 113 missions of space shuttle flight.

And we mourn the seven astronauts, who showed us how to explore, how to imagine, how to live.

Better than all of us, they knew the risk of the flight they took. They loved the thrill, they loved the rush.

They took that chance not for their gain but to advance the lives of all of us, regardless of nation or creed or color.

Their willingness to work together is an attitude we all should adopt.

Their dream of discovery is one we all must continue.

And we owe it to them to continue to reach, literally, for the stars.