Nasa aims to land on asteroids

Nasa's mission to land on an asteroid could help save the Earth, the space agency has revealed.
The mission is expected to test an 'enhanced gravity tractor' that could be used to push away an asteroid on a collision course with Earth. The technique would use a robotic probe to fly alongside a space rock for months or years, gradually nudging it off course with slight gravitational changes caused by taking boulders from the surface.
"We'd go into this enhanced gravity tractor position after we retrieve the boulder and demonstrate that we have even more gravity attraction capability by doing that," Lindley Johnson, program executive for Nasa's Near-Earth Object observations programme, told reporters in March.
The mission is being touted as a major step on the way to Mars. Nasa hopes to find an asteroid which is between seven and 10m wide for its mission.
They would then tow or push it towards Earth so that it ends up in a stable orbit near the moon.
In 2021 astronauts would then use an Orion capsule - a manned spacecraft - to land on the asteroid and bring back soil and rock samples for analysis.
This asteroid would also, probably in the 2030s, be used as a stop-off point for astronauts on their way to Mars.
Exact details on how Nasa plans to pluck an asteroid out of its trajectory are not yet known, but the most recent rendering shows it is captured and held inside what looks like a giant plastic bag.
Nasa has revealed two of its astronaut's have started training for an ambitious real life mission to land on an asteroid as a stepping stone to Mars.
On Friday, it revealed preparations for the mission were underwater in a giant water tank used to simulate weightlessness. The space agency plans to land astronauts on an asteroid in the 2030s.