In a step toward returning to the moon, NASA announced today that it had selected nine companies that will vie for contracts to take small payloads for the space agency to the surface of the moon.

“We are building a domestic American capability to get back and forth to the surface of the moon,” said Jim Bridenstine, the NASA administrator. NASA astronauts last landed there in 1972, and no U.S. spacecraft has touched down on the lunar surface in one piece since then.

Cumulatively, the contracts could be worth up to $2.6 billion over 10 years. Flights could begin as soon as next year, and NASA officials are aiming for two a year, or about 20 in all.

These spacecraft would be far too small for people, but they could carry scientific experiments to the moon, and help NASA scout and study potential locations for lunar bases, particularly in the eternally shadowed craters near the poles that are filled with frozen water.

The companies, a mix of established NASA contractors and space startups, are:

>> Astrobotic Technology of Pittsburgh

>> Deep Space Systems of Littleton, Colorado

>> Draper of Cambridge, Massachusetts

>> Firefly Aerospace of Cedar Park, Texas

>> Intuitive Machines of Houston

>> Lockheed Martin of Littleton, Colorado

>> Masten Space Systems of Mojave, California

>> Moon Express of Cape Canaveral, Florida

>> Orbit Beyond of Edison, New Jersey

NASA officials said they did not expect all of the companies to succeed. Rather, they likened the effort to high-risk, high-reward bets by venture capital investors.

The Trump administration has put an emphasis on sending NASA astronauts to the moon for the first time since Apollo 17 in 1972. NASA has not yet laid out detailed plans or how much that might cost.

The new program reflects a more commercial approach by NASA, similar to its hiring of commercial companies to take cargo, and soon astronauts, to the International Space Station.

Instead of NASA engineers designing the spacecraft themselves, the space agency is publishing the capabilities it needs and requesting proposals for how to provide those services from companies.

That approach will be less expensive, and NASA will just be one customer of many customers, Bridenstine said.