Asteroids have made people nervous for several decades now, ever since scientists declared that a large object from space smashed into 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.

Untold thousands of asteroids the size of warehouses orbit the sun near Earth, and some of them are enticingly rich in water and precious metals. The water could be processed to create fuel depots for spaceships, not to mention beverages for astronauts. The metals, including platinum, could be mined and brought back to Earth.

It’s a big idea whose time has come, at least on the West Coast. The entrepreneurs unveiled their plan at a Tuesday news conference at the Museum of Flight in Seattle.

“This is directly in line with every major exploration that ­humanity has done,” space visionary Peter Diamandis said in an interview earlier in the day. “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 colleague Eric Anderson have formed Planetary Resources Inc., the world’s first asteroid-mining business.

“We’re now going to bring the solar system to within our economic sphere of influence,” Anderson said, standing at a podium in front of a banner that read “Redefining Natural Resources.”

The idea of extracting resources from asteroids is not new, and even predates the Space Age. It has been championed in recent decades by planetary scientist John S. Lewis, author of the book “Mining the Sky” and one of the company’s advisers.

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 a formidable array of 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 exploring the deepest trench in the ocean. Another adviser is former NASA astronaut and Northern Virginia resident Tom Jones.

“This is an American story,” Perot said by phone at the news conference. “One more time you see the private sector in America generate these great ideas.”

Diamandis and Anderson dreamed up the asteroid-mining venture about three years ago after having success with other commercial space efforts, including suborbital flights for space tourists. They’ve hired as their top engineer a former NASA manager, Chris Lewicki, who worked on Mars missions at NASA’s Jet Propulsion Laboratory.

The company will design a fleet of small, relatively cheap asteroid-prospecting spacecraft. The robotic devices will go into space in a “ride sharing” status on commercial rockets. The company officials said the first launch will be within two years, and it might take a decade to identify the first asteroid to be mined.

“This company is not about thinking and dreaming about asteroid mining,” Anderson said. “It’s about building real hardware. It’s about doing real things in space.”

Diamandis and Anderson stressed that they are not trying to circumvent NASA, which has been going through a difficult transition period since the retirement of the space shuttle.

“We’re building a gas station . . . to carry out their mission in deep space,” Anderson said in an interview.

NASA has a long-term plan to build a new, heavy-lift rocket, dubbed the Space Launch System, that could go beyond low Earth orbit. One likely destination would be a near-Earth asteroid. Critics have assailed NASA’s strategy as aimless, and have criticized the Obama administration for canceling an earlier plan to return to the moon.

“This project aligns well with our national space policies and goals,” NASA spokesman David S. Weaver said in an e-mailed statement Tuesday, adding that as the space agency moves toward sending humans to an asteroid for the first time, “we will certainly look to take advantage of private-sector resources and data.”

Scott Pace, director of the Space Policy Institute at George Washington University, called the Planetary Resources team impressive and applauded the effort, but he added, “If there were a credible human lunar exploration effort underway, the economic case for exploiting lunar or in-space water sources would be clearer.”

Water is essential to spaceflight. It can be processed for fuel, or to create oxygen, or used for drinking or growing plants, Anderson said. Even a modest-size rock, just 50 yards or so across, contains a massive amount of water worth billions of dollars, Anderson said.

Jones said at the press conference that it currently costs $20,000 per liter — nearly $76,000 a gallon — to launchwater from the surface of Earth into orbit. Anderson said his company might be able to offer NASA water for a 10th of that price, or less.