As space shuttle astronauts completed construction of the $100-billion International Space Station this week, NASA turned its attention toward a new exploration initiation: getting to an asteroid.
The agency will use the Orion moonship from its canceled Constellation program to carry crews into deep space, beyond the space station's 220-mile-high orbit where the shuttles cannot go.
The unimaginatively named Multi-Purpose Crew Vehicle is intended to carry four-person crews on flights lasting up to 21 days. For longer missions to an asteroid or Mars, the capsule would be attached to a larger second ship.
"This vehicle is primarily for launch and entry with in-space capabilities for certain periods of time," NASA's head of exploration, Doug Cooke, told reporters on a conference call. "Generally, for long-term missions, we would assume we have in-space habitation in a larger module just because the crew needs more space for a longer period of time."
The agency plans to announce in June what heavy-lift rocket it will build or buy to send astronauts beyond Earth's orbit. Top on the list of places to visit is an asteroid and NASA this week made progress on that front as well, selecting an ambitious sample return mission known as OSIRIS-Rex.
Though chosen for its scientific allure, the mission will moonlight as a flight test for future human expeditions.
"Before human exploration of asteroids can take place, there must be precursor missions that characterize the environment and allow astronauts to operate safely there," University of Central Florida astrophysicist Humberto Campins wrote in an email to Discovery News.
OSIRIS-Rex -- an acronym for Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer -- will be the first attempt to return samples from a carbon-containing asteroid. Though bits of asteroids regularly fall to Earth in the form of meteorites, carbon has never been found to survive the process.
The probe's target is a dark, pristine 1,900-foot-wide asteroid called 1999 RQ36. After launch in 2016, NASA plans to loop the spacecraft around the sun until it reaches the asteroid's orbit, then have it formation-fly for about a year while scientists conduct an initial round of studies and figure out where to touch down.
Asteroids have virtually no gravity, so "landing" on one is a bit of a misnomer. "It's more like kiss," said lead scientist Michael Drake, with the University of Arizona.
Eventually, the probe will reach out its robot arm and collect up to about five pounds of rock, dust and organic material. The cache will be sealed in a container and returned to Earth, parachuting down over Utah in 2023.
Drake says the asteroid is "like a time capsule containing probably the building blocks of life."
For NASA, which is ending its 30-year-old shuttle program this summer, the asteroid mission could be the beginning of its next one.