Why do the world's two richest men want to get off the planet so badly?
Elon Musk of Tesla and Jeff Bezos of Amazon have more than $350 billion in combined wealth and preside over two of the most valuable companies ever created. But when they're not innovating on Earth, they have been focusing their considerable brain power on bringing a multiplanetary human habitat to reality.
For Musk, it's through his other company, SpaceX, which has become an ever bigger player in the private space-technology arena. On top of satellite launches and other rocket innovations, the company announced it will send its first "all civilian" crew into orbit at the end of the year, in a mission called Inspiration4. SpaceX has already carried NASA astronauts to the International Space Station and is planning to transport more, as well as private astronauts, for a high price.
Most ambitiously, Musk has said that SpaceX will land humans on Mars by 2026. To do that, the private company will use a chunk of the close to $3 billion — including $850 million announced this week in a regulatory filing — that it has raised over the last year to finance this herculean effort.
While Musk might not be the first human to go to the red planet, he once told me that he wanted to die there, joking, "Just not on landing."
Bezos, who is stepping down as chief executive of Amazon this year, is expected to accelerate his space-travel efforts through his company Blue Origin, whose tag line reads, in part, "Earth, in all its beauty, is just our starting place."
Like SpaceX, Blue Origin is working on payload launches and reusable orbital launch vehicles, as well as on moon landing technology, to achieve what Bezos once called "low-cost access to space." Blue Origin executives said recently that the company is close to blasting off into space with humans.

Bezos' most extravagant notion, unveiled in 2019, is a vision of space colonies — spinning cylinders floating out there with all kinds of environments.