Many pupils now dreaming of becoming astronauts will eventually orbit the earth, Professor Sir Martin Rees, the Astromomer Royal, told the Festival.
"Some may walk on Mars, and many will go into earth orbit," Sir Martin said. But they will need to be tough, he added, because it will be like the Wild West.
Private consortia that are willing to accept great risks will dominate space exploration. "It will happen in a boisterous and disorganised way," Sir Martin said.
Governments are likely to be more restrained explorers, as seen in their exploration of Antarctica. "If the first people to go to Mars are privately-funded adventurers, then the Wild West model will be more likely to prevail," he said.
Sir Martin also depicted a future of super-evolved "post-humans" undertaking interstellar travel. "With modern genetic techniques the human species may look quite different within a few centuries."