Free Astronomy Magazine July-August 2018

10 JULY-AUGUST 2018 ASTRONAUTICS mate by Elvis, 4% of the 17,000 NEAs could be metallic − the same percentage of metal- lic meteorites that fall on the Earth com- pared to the total number of meteorites. This assessment (a possibly questionable es- timate, based only on as- sumptions and probabili- ties) and other more strin- gent parameters led Elvis to say that the potentially profitable asteroids number just a dozen. Unfortunately, of this estimated dozen, we do not yet know where they are or what they may actu- ally contain. So the survey starts from scratch, the primary goal being to find that handful of NEAs in the multitude of those already discovered and the many still to be discovered. To find them, researchers intend to organize a network of ground-based telescopes of a 2-3m class, able to perform spectrophoto- metric observations in the infrared − and T he models of mining facili- ties clinging to the two NEAs de- picted on this page highlight the need to firmly anchor the struc- tures to the sur- face. Indeed, due to the feeble gravity of these asteroids, the pressure exerted by the excavators could otherwise be sufficient to lift the plants off the surface.