One way to transport the metals back would be to mine them on Eros and send the refined ore to Earth. It takes about 2,000 calories to boil a gram of iron, so the equivalent of 20,000-200,000 megatonnes of TNT would be needed to start liberating substantial quantities of iron from the asteroid The energy could be obtained from the Sun. If you wanted to mine one section of Eros at a time, a huge solar energy collector – a sheet only a few kilometres in size – could collect enough energy to power a smelting plant on Eros.Those are all “guesstimate” figures. But they show how mining one small asteroid such as Eros would revolutionise the availability of many raw materials on Earth There is another reason to take a keen interest in Eros. Take what is left and heat it in a solar furnace – huge mirrors made of foil will do – and all sorts of useful material will be vaporised that can be extracted with the kind of condenser seen in any oil refinery. Standing on one of those would be a hazardous occupation, as too vigorous a step would send you careering off into space.
Lift a piece of rock and drop it, and it would take five minutes to reach the ground.Mining the metal would not be complicated. Scoop the surface (it will be loose) and crush the fragments in a centrifuge, extracting metal fragments with a magnet. Its nickel would satisfy us for one millennium, its cobalt for several. The fact is, a smallish, 1km asteroid contains about eight billion tonnes of metal, worth over $50,000,000bn Its iron and copper could supply the Earth for a decade. Forget conventional mining and all its environmental problems.
One Eros in orbit around the Earth, or preferably the Moon, is all we would need for almost all time But perhaps Eros is not the right asteroid to mine Better would be the more numerous 100-metre ones. Such mineral riches, yet you could walk round it in 15 minutes.Near will be circling the 2,900 cubic km of Eros, in which there is more aluminium, gold, silver, zinc and other base and precious metals than has ever been mined or indeed ever could be from the outer layers of Earth’s crust. So, for the second time, Near is approaching Eros.The craft will tell us more about asteroids in just a few weeks than we have ever learnt. What we know already should fascinate us, for asteroids may play a role in the economic and technological development of Earth.
When they regained control, it was clear it was too late to orbit Eros. Emergency observations of it were made as it went sailing by in the interplanetary dark. Another rocket, fired in January 1999, put it back on course for the rendezvous, but this time it would be a year away on the other side of the Sun. The rocket shut down after only two seconds, and mission controllers had to scramble to rescue the spacecraft. A near infra-red spectrometer will map out the surface composition.Near’s path to Eros has been a rocky one, so to speak. The craft was launched flawlessly in February 1996, and in June 1997 it flew past the large, dark asteroid Mathilde. So angular was that tiny world, that, when approaching from its dark side, Near’s camera was able to see only a series of rocky ridges with deep shadows in between.
