Free Astronomy Magazine July-August 2018

9 JULY-AUGUST 2018 the same composition as other, better known, dynamically-comparable objects be- longing to the same family or shared ances- tor. Nonetheless, the level of uncertainty remains high. This has not been a major problem up to now, but becomes one as we plan the mining exploitation of those bod- ies, when it is essential to know in advance where to go digging and what we can ex- pect to extract. Since asteroids can be roughly divided into carbonaceous, siliceous and metallic cate- gories, one can imagine that robotic miners will be exposed to very different character- istics depending on the surfaces they land on and drill into. Mining companies are par- ticularly interested in metal asteroids be- cause they are rich in iron and nickel. The experience of terrestrial miners tells us that, where iron and nickel are present, gold and platinum can also often be found. According to Martin Elvis (Harvard-Smith- sonian Center for Astrophysics), for a com- pany to be profitable in light of the enor- mous investments needed to mine an aster- oid, it must produce at least $1 billion, a threshold perhaps reachable if the asteroid has a diameter greater than 1 km and 10 parts per million or more of platinum. NEA composition is not the only factor, as the as- teroid must also have orbital properties very favorable for a rendezvous, such as being able to be brought to a relative speed with respect to the Earth of less than 4.5 m/s. How many NEAs do exist with these mini- mum requirements? According to an esti- to determine the mineralogical composi- tions of their surfaces. With knowledge of the orbit of a given asteroid, we can only hypothesize that it inherited its chemical el- ements from the early protoplanetary disk at that distance from the Sun, or that it has I n the video above, a sample is taken from an asteroidal sur- face, according to Deep Space Industries. Deep Space Industries - Bryan Versteeg