Once a wacky idea, commercial asteroid exploration has become a race, with the launch of a second company focused on mining near-Earth space rocks. The newly launched firm plans to survey asteroids, tap them for resources and shape the raw materials into products using 3D printers in space.

Deep Space Industries (DSI) of McLean, Virginia, held a press event at the Santa Monica Museum of Flight in California on Tuesday. "Our business plan is to get into this field as it begins, and it is beginning today," said founder and chairman Rick Tumlinson.

To illustrate the company's ambition, he evoked 19th century pioneers, Meriwether Lewis and William Clark, who led the first transcontinental US expedition to the Pacific Ocean. "We want to build on the Lewis and Clark legacy of our government space programme and open it up for the settlers and shopkeepers."

The announcement follows the first commercial plan to mine asteroids for precious metals and other resources, announced last April by Planetary Resources of Bellevue, Washington.

Asteroids are full of potentially valuable materials, including nickel, as well as water and gases that could be used to make fuel for future space missions. But much of their value comes from the fact that they're already in space.

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