WASHINGTON — Asteroids have made people nervous for several decades now, ever since scientists declared that a large object from space smashed into the Earth 65 million years ago and put the kibosh on the Age of Dinosaurs. But now some entrepreneurs and tech tycoons are declaring that there’s money in those space rocks.

Don’t fear them, they say. Mine them.

Asteroids are full of water and precious metals. The water could be processed to create fuel depots for spaceships; the metals could be mined and brought back to Earth.

“This is directly in line with every major exploration that humanity has done,” space visionary Peter Diamandis said in an interview Tuesday morning. “It is in line with Magellan, and Columbus, all the great explorers in the 1400s and 1500s, crossing the Atlantic and looking for resources.”

Diamandis and space entrepreneur Eric Anderson held a much-hyped news conference Tuesday in Seattle to announce the formation of Planetary Resources Inc., their asteroid-mining venture.

The idea of extracting resources from asteroids is actually an old one, bandied about for decades. Any such venture has the obvious challenge of convincing people that it is not a pie-in-the-sky concept.

But this one can brag that it has some well-known tech tycoons as backers. The company says the investors include Google co-founder Larry Page, Google Chairman Eric Schmidt, Google investor K. Ram Shriram, former Microsoft chief software engineer Charles Simonyi and H. Ross Perot Jr., son of the famed businessman and former presidential candidate.

Also in the mix, serving as an adviser, is the ubiquitous James Cameron, who recently emerged from the deepest trench in the ocean.

Diamandis and Anderson dreamed up the asteroid-mining idea about three years ago after having success with other commercial space ventures, including suborbital flights for space tourists. They’ve hired a former NASA manager, Chris Lewicki, who worked on Mars missions at NASA’s Jet Propulsion Laboratory. The company will design the hardware for mining the asteroids and will purchase flights into space from commercial launch companies.

Diamandis and Anderson stressed in The Post interview that they are not trying to circumvent NASA, which has been going through a difficult transition period since the retirement of the space shuttle. On the contrary, they would like to be NASA’s fuel suppliers.

“What we’re doing is very much aligned with national space goals and NASA,” Anderson said. “We’re building a gas station for these kinds of rockets to carry out their mission.”

He continued: “We have gone out into the world to find money that would otherwise not be available for projects in space. We are prepared to take the early risks so that the U.S. government would be the beneficiary down the road.”

The asteroids in question are in near-Earth orbits, and even a modest-sized rock, just 50 yards or so across, contains a massive amount of water, Anderson said.

Water is essential to space flight. It can be processed for fuel, or to create oxygen, or used for drinking or growing plants, Anderson said. But he said it currently costs $20,000 per kilogram – more than $9,000 a pound – to launch from the surface of the Earth into orbit. He said his company might be able to offer NASA water for a 10th of that price, or even a 20th.

Conceivably, an asteroid could be propelled closer to Earth, to put it in a more convenient location for mining, but Anderson said that it might also be kept right where it currently orbits.

And it’s all doable with current technology, he said. There’s no “law-of-physics type show-stopper,” he said.