Artists illustration showing SpaceX's Dragon spacecraft landing on Mars.

SAN FRANCISCO Humanity shouldn't dally in its quest to colonize Mars, SpaceX's billionaire founder and CEO Elon Musk says.

"Now is the first time in the history of Earth that the window is open, where it's possible for us to extend life to another planet," Musk told a huge crowd here Tuesday (Dec. 15) at the annual winter meeting of the American Geophysical Union (AGU).

"That window may be open for a long time and hopefully it is but it also may be open for a short time," he added. "I think the wise move is to make life multiplanetary while we can." [SpaceX's Plan for Mars & Reusable Rockets (Video)]

SpaceX founder and CEO Elon Musk talks to Margaret Leinen, the director of the Scripps Institution of Oceanography, on Dec. 15, 2015, at the annual fall meeting of the American Geophysical Union in San Francisco.

Colonizing Mars has long been a passion of Musk's. Indeed, the entrepreneur has repeatedly said that he founded SpaceX in 2002 primarily to help make humanity a multiplanet species. Having a self-sustaining outpost on the Red Planet would serve as an insurance policy, making humanity's extinction unlikely even if something goes terribly awry here on Earth, Musk said Tuesday.

Colonizing Mars would have other benefits as well, he added; the effort would greatly advance science discoveries and technological capabilities, and it would help inspire and excite people from all walks of life and from all around the globe.

Mars settlement "would be a great adventure," Musk said. "There need to be things that people look forward to when we wake up in the morning."

Colonizing Mars won't be easy, but humanity can do it with a few key technological advances, Elon Musk said. Chief among them are fully and rapidly reusable rockets, and the ability to produce rocket propellant from local materials on the Red Planet.

Currently, rockets are used just once and then ditched into the ocean. That means a lot of money is sinking to the ocean floor after every launch.

For example, SpaceX's Falcon 9 rocket costs about $16 million to build, but the fuel for each of the booster's liftoffs costs just $200,000, Musk said Tuesday. So finding a way to fly rockets again and again has the potential to slash the cost of spaceflight by a factor of 100, he added.

SpaceX is working hard to do just that. The company has tried twice this year to land a Falcon 9 first stage on an "autonomous drone ship" in the Atlantic Ocean during orbital launches. Both attempts, which occurred in January and April, were near misses; the rocket stage hit the target but ended up toppling and exploding on the ship's deck.

SpaceX will try again soon to bring a Falcon 9 first stage back down for a soft landing this time, perhaps on land at Cape Canaveral Air Force Station in Florida, Musk said recently.

Mars colonization could be complicated by the discovery of indigenous life forms on the surface, Musk said Tuesday; in such a case, scientists and decision makers would have to make sure Red Planet pioneers tread as carefully as possible.

But Musk doesn't think such planetary-protection concerns will end up being a major issue.

"It really doesn't seem like there's any life on Mars, on the surface at least," Musk said here Tuesday. "We're not seeing any sign of that."

The Martian underground is more hospitable, since any life forms there would be protected from the harsh radiation environment and cold temperatures encountered on the surface, he added. But Musk doesnt think subsurface life would or should derail Red Planet colonization.

"I think anything we do on the surface is really not going to have a big impact on the subterranean life," he said.

Musk hopes to be a key player in the spread of humanity to another planet, but he doesn't expect to be around to see the full fruits of his labor.

"It will be superhard to do this, and it will take a long time," he said of Mars colonization. "I suspect I won't live to see it become self-sustaining."

Follow Mike Wall on Twitter@michaeldwallandGoogle+.Follow us @Spacedotcom, Facebookor Google+. Originally published onSpace.com.

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Now Is the Time to Colonize Mars, Elon Musk Says