The Asteroid Redirect Mission (ARM) isn't due to launch until mid-2020s, but NASA has announced details about the agency's plan to test new capabilities that will come in handy for deep-space expeditions in the future.

For ARM, a spacecraft will be capturing a boulder from a near-Earth asteroid's surface, moving it into stable orbit around the moon to be explored by astronauts.

According to Robert Lightfoot, associate administrator for NASA, ARM offers the opportunity to initially demonstrate what several technologies can do and how these can be of benefit to astronauts. Retrieving a boulder might not sound exciting, but it will directly impact future planning for deep-space human missions.

NASA won't be announcing the specific asteroid targeted for ARM until 2019, about a year before the mission's spacecraft is launched. To be considered a candidate, an asteroid must be examined by scientists, assessed for its precise orbit, shape, rotation and size. So far, three valid candidates have been identified: 2008 EV5, Bennu and Itokawa. NASA looks to add one or two to the list of candidate asteroids every year until the mission is ready to launch.

The robotic spacecraft will be evaluating technologies, such as the Solar Electric Propulsion. SEP is an important technology because it converts sunlight into electricity, which is then used to propel charged atoms to give the spacecraft a boost. This propulsion method allows for big cargo to be moved more efficiently and requires fewer launches and less propellant, helping reduce mission costs.

It's also possible for SEP spacecraft to place vehicles or cargo at certain spots in space for easier retrieval by crews in Mars or staged as waypoints for those headed to the Red Planet.

ARM will also be used for testing planetary defense techniques that will help NASA in devising strategies for mitigating potential threats presented by asteroid impacts. As the mission will be essentially moving an asteroid, it will give the agency insight into how best to put space rocks off course when the need arises.

"Asteroids are a hot topic, not just because they could pose a threat to Earth, but also for their scientific value and NASA's planned mission to one as a stepping stone to Mars," added Jim Green, director for NASA Planetary Science.

It is estimated that it will take about six years to move a boulder from an asteroid into the moon's orbit.