Nasa will use a robotic arm to grab a boulder and send it into orbit around the moon, giving it its own moon, allowing astronauts to study the rock as it flies around the Earth.

The Asteroid Redirect Mission (ARM) will also allow Nasa to demonstrate many of the technologies that will carry humans to Mars. "The option to retrieve a boulder from an asteroid will have a direct impact on planning for future human missions to deep space and begin a new era of spaceflight," said Nasa associate administrator Robert Lightfoot.

The technology used could also help Nasa defend the planet from future asteroid impacts. During the mission, the agency will try out the techniques that it could use to throw an asteroid off course if it were coming towards Earth.

An astronaut, anchored to a foot restraint, prepares to investigate the asteroid boulder. (Nasa)

Nasa refers to the robotic arm plan as “option B”, and was selected over another plan that would see an entire asteroid redirected. In the successful plan, a robotic arm will land on an asteroid big enough to have suitable boulders on it, and then throw one of those into orbit around the moon.

Nasa said that it will pick an asteroid no earlier than 2019, and will launch the spacecraft carrying the throwing robot about a year later. Nasa has identified three candidates already — and expects to find one or two more per year — all of which will be examined for their shape, size, orbit and other characteristics before they are chosen.

Once the boulder is secured, the Capture and Restraint System legs will provide a mechanical push off that will separate the boulder from the surface and provide an initial ascent without the use of thrusters to limit the amount of debris created (Nasa)

When the asteroid is chosen, and the craft landed on it, robot arms will be deployed to grab a boulder. The unmanned ship will then send the boulder into orbit over a number of years.

The same technology could be used in future to save us from asteroids that are headed towards the earth. The robot could eventually defend the planet by using a technique called a “gravity tractor” — if it heads towards the asteroid, the robot’s gravity can throw off the course of an asteroid without touching it. That will work even better if the robot can successfully grab a boulder, giving it more mass and more gravitational pull.

The Asteroid Redirect Vehicle conducts one of the 1 km fly-bys that are used to characterize and image the asteroid with a resolution of up to 1 cm. (Nasa)

The mission will also be testing out technologies for future missions into deep space.

The plan will make use of Solar Electric Propulsion, for instance, which allows spacecraft to convert sunlight into electric power and use that to move through space. Using that technique is less efficient than burning fuel, but means that space missions will need much less fuel and fewer launches, bringing down costs.

Microspine grippers on the end of the robotics arms are used to grasp and secure the boulder. The microspines use thousands of small spines to dig into the boulder and create a strong grip. An integrated drill will be used to provide final anchoring of the boulder to the capture mechanism (Nasa)

That technology could eventually be used to send out cargo or vehicles to be picked up by astronauts on their way to Mars. Objects could be sent out into space to work as a waypoint, or be ready for humans when they arrive on the red planet. It will also give a chance to use new systems, as astronauts head out to the asteroid to study it. They will be able to jump out of the Orion space capsule, wearing new space suits designed for deep space missions, and collect samples that could then be returned to Earth for study.

"Asteroids are a hot topic," said Jim Green, director of NASA Planetary Science. "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."

Where to explore in the solar system Show all 10 1 /10 Where to explore in the solar system Where to explore in the solar system Mars - Olympus Mons Olympus Mons is the largest volcano in the Solar System. At 22km high Olympus Mons is nearly three times as high as Mt Everest Where to explore in the solar system Mars - Mount Sharp Mount Sharp is the current focus point of the Mars Science Laboratory’s Curiosity rover. Sitting at the forefront of Martian research this location will hopefully unlock the secrets of Mars’s past. Where to explore in the solar system Ida and Dactyl Nestled deep within the asteroid belt is the asteroid 243 Ida. During a fly by of the Galileo space probe it was discovered that Ida had a companion. Orbiting around Ida was a tiny moon that was named Dactyl. Where to explore in the solar system Jupiter - The Red Spot Getting tired of leisurely cruises through the Caribbean? Why not float a dirigible through one of the oldest known storms in the Solar System. Jupiter’s Great Red Spot is large enough to contain three Earths and has been present for over 300 years. Where to explore in the solar system Moon - Sea of Tranquility As the landing site of the first ever humans to set foot on the Moon who wouldn’t want to walk in the footsteps on Neil Armstrong on the Sea of Tranquility? Where to explore in the solar system Europa - Underwater seas Europa’s underwater seas are one of the strongest candidates for potential life outside Earth. Scientists are waiting the day we can probe their icy depths. Where to explore in the solar system Titan - Methane Lakes Saturn’s Moon Titan is home to a nice thick atmosphere. Similar to the Earth it supports a full weather cycle. Unlike the Earth, rather than using water, Titan’s cycle is based on methane, often found in gas cookers here on Earth. Where to explore in the solar system Mimas, the Death Moon What better location for a holiday snap. The large Herschel crater on Mimas gives this moon an appearance of a certain dark lords ultimate weapon. When viewed from the right angle it appears that the Death Star is in orbit around Saturn. Where to explore in the solar system Venus The thick clouds of Venus make it an extremely mysterious place. It also has some of the most extreme weather we can find. Runaway greenhouse gases have shrouded the planet in a thick layer of cloud, heating it to nearly 600°C. It is also home to sulphuric acid rain and crushing atmospheric pressure. Make sure you pack a sturdy umbrella! Where to explore in the solar system Oceans of Earth One of the most unexplored places in the Solar System is our own oceans. 70% of the Earth is covered in ocean and as of yet we have only explored around 10% of them. With so much water to explore who knows what we may find lurking in the depths. NASA

Nasa has been receiving more and more money from the US Congress to fund its asteroid observations work, known as the Near-Earth Object Observations Program. It has been finding an increasing number of near-Earth objects, helping find rocks that could pose a threat to life on Earth.