"Mars can't just be a one-shot mission," says Apollo 11 astronaut Edwin "Buzz" Aldrin, the second person to walk on the moon.
He's part of a group who met last week in Washington DC for the first Human to Mars Summit, or H2M. The astronauts, researchers and space flight firms aim to chart a path to the Red Planet by 2030.
And they are thinking beyond mere visits. Though it won't be easy, they say establishing a permanent, sustainable outpost on the Red Planet may be our civilisation's only chance of long-term continuity.
"Single-planet species don't survive," says former astronaut John Grunsfeld, who still works at NASA. "That's a pretty sound theorem – just look at the dinosaurs. But we don't want to prove it."
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