Some day, the platinum, cobalt and other valuable elements from asteroids may even be returned to Earth for profit. At 1997 prices, a relatively small metallic asteroid with a diameter of 1.6 km (1 mile) contains more than $20 trillion US dollars worth of industrial and precious metals. In fact, all the gold, cobalt, iron, manganese, molybdenum, nickel, osmium, palladium, platinum, rhenium, rhodium and ruthenium that we now mine from the Earth's crust, and that are essential for economic and technological progress, came originally from the rain of asteroids that hit the Earth after the crust cooled. This is because, while asteroids and the Earth congealed from the same starting materials, Earth's massive gravity pulled all such siderophilic (iron loving) elements into the planet's core during its molten youth more than four billion years ago. Initially, this left the crust utterly depleted of such valuable elements. Asteroid impacts re-infused the depleted crust with metals.
In 2004, the world production of iron ore exceeded a billion metric tons. In comparison, a comparatively small M-type asteroid with a mean diameter of 1 km could contain more than two billion metric tons of iron-nickel ore, or two to three times the annual production for 2004. The asteroid 16 Psyche is believed to contain 1.7×1019 kg of nickel-iron, which could supply the 2004 world production requirement for several million years. A small portion of the extracted material would also contain precious metals.
In 2006, the Keck Observatory announced that the binary Trojan asteroid 617 Patroclus,and possibly large numbers of other Jupiter Trojan asteroids, are likely extinct comets and consist largely of water ice. Similarly, Jupiter-family comets, and possible near-Earth asteroids which are defunct comets, might also economically provide water. The process of in-situ resource utilization (bootstrapping)—using materials native to space for propellant, tankage, radiation shielding, and other high-mass components of space infrastructure—could lead to radical reductions in its cost.