The first four astronauts to be trained to pilot the next generation of American spacecraft have been chosen and they include a woman who has already lived in space for 10 months.

"These distinguished, veteran astronauts are blazing a new trail, a trail that will one day land them in the history books and Americans on the surface of Mars," NASA Administrator Charles Bolden said in an announcement Thursday.

The astronauts include:

Robert Behnken, 45 -- U.S. Air Force colonel from Maryland, flew two space shuttle missions

Sunita Williams, 49 -- U.S. Navy helicopter pilot from Massachusetts, spent 322 days in space on two missions

Eric Boe, 50 -- U.S. Air Force test pilot from Georgia, flew on two space shuttle missions

Douglas Hurley, 48 -- Retired U.S. Marine test pilot from New York, piloted two space shuttle missions

The first launch of the commercially-produced spacecraft is expected in 2017, although it would have been this year if Congress had approved NASA's budget requests, Bolden said.

"We are on a Journey to Mars, and in order to meet our goals for sending American astronauts to the Red Planet in the 2030s we need to be able to focus both on deep space and the groundbreaking work being done on the International Space Station (ISS)," Bolden said. "Our commercial crew initiative makes these parallel endeavors possible. By working with American companies to get our astronauts to the ISS, NASA is able to focus on game-changing technologies, the Orion spacecraft and the Space Launch System (SLS) rocket that are geared toward getting astronauts to deep space."

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