Small Near-Earth Asteroid Surfaces Have Few Precious Metals, Study Finds

RockDoctor (Slashdot reader #15,477) writes:

A recent paper on ArXiv reports new spectroscopic analyses of the surfaces of 42 asteroids. The main result for space enthusiasts is that there is not one 'M' class asteroid (metal-rich) surface in the collection.
The imagery that (many) people grow up with from Hollywood and TV 'science' 'documentaries' is that the Solar system is full of asteroids which are made of metal ready for mining to produce solid ingots of precious metals. That's Hollywood, not reality. This result is about what you'd expect from the proportion of metallic asteroids — otherwise estimated at about 0.5% of the population.
The asteroid mining fraternity dream of taking apart an M-type asteroid like Psyche, which is fair enough as a dream. Even as a dream for 'asteroid mining' metal market speculators. But they are relatively rare asteroids. A realistic 'ISRU' (In-Situ Resource Utilisation) plan is going to have to expect to digest around 200 silicate mineral (and clay ('phyllosilicate'), and ice) asteroids for every metallic one they digest.

Here's the home page for the project.

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