More recently , radar-based techniques have also been deployed to distinguish different types of an asteroid . Such estimates of asteroid composition are often calibrated against samples of meteorites found on Earth .
The relatively high abundance of rare metals in asteroids allows them to be ranked according to their approximate value and relative difficulty to harvest . A few companies have even been founded to explore the possibility of extracting heavy metals from near-earth asteroids ( NEAs ).
A challenging mission
A 2012 feasibility study at the California Institute of Technology ( CalTech ) in Pasadena , US , argues that the most attainable first mining project would consist of bringing an NEA into high-lunar orbit , and making it accessible for surveying and material extraction . They estimated that it would be feasible to redirect an asteroid approximately 7m across to orbit the moon by 2025 . However , the same study estimates the cost of the mission to be at least $ 2.6 billion .
Bringing an asteroid close enough to Earth to extract valuable materials depends on more than just the distance and size of the asteroid . One of the most important factors is the change in the asteroid ’ s velocity , or ‘ delta V ’, which would be required to alter the asteroid ’ s trajectory to one that would put it in orbit around Earth or the moon . The amount of fuel required to push the asteroid would depend on both
▲ This mosaic image of asteroid Bennu is composed of 12 PolyCam images collected on Dec . 2 by the OSIRIS-REx spacecraft from a range of 15 miles ( 24 kilometers ). The image was obtained at a 50 ° phase angle between the spacecraft , asteroid and the Sun , and in it , Bennu spans approximately 1,500 pixels in the camera ’ s field of view . Source : NASA / Goddard / University of Arizona
10