Billionaires Elon Musk and Jeff Bezos are casting the fortunes they've spent on building new rockets to help humankind escape our home planet as a far greater legacy than funding more terrestrial good deeds.

The big picture: They're reframing for-profit businesses — SpaceX and Blue Origin — in philanthropic terms.

Musk spent $100 million to get SpaceX off the ground in 2006.

On the other hand, his private charity, the Musk Foundation, started in 2001, gave away $54 million over 15 years to environmental, educational, medical and other causes, according to an analysis by The Guardian. (He has also signed the Giving Pledge.)

“We’re faced with a choice: Which future do you want?" Musk said at the unveiling of SpaceX's Starship in September.

"Do you want the future where we become a space-faring civilization and are on many worlds and are out there among the stars, or one where we are forever confined to Earth?”

Bezos has reportedly funneled $1 billion a year into Blue Origin — compared with recent grants of $98.5 million focused on homelessness and education from his year-old philanthropy, the Bezos Day One Fund, that was seeded with $2 billion.

As for space travel, “I think it is important for this planet," Bezos told CBS in July.

"I think it’s important for the dynamism of future generations. It is something I care deeply about. And it is something I have been thinking about all my life.”

Both billionaires believe the only way for humanity to survive as a species is to go to space — to provide an insurance policy against damage to Earth, or allow harmful activities to be moved off-world.

But critics say there are risks of having mankind's course in space shaped by a few —including ethical questions about who owns (and profits from) space, and concerns over repeating the negative consequences of earthly colonization.

Keep in mind: SpaceX brings in billions from government and commercial contracts, and Blue Origin is chasing after those contracts to get its launch business up and running.

The bottom line: The Bezos-and-Musk brand of philanthropy says, in effect: “My big contribution to human knowledge and understanding is my space company.”

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