Why We Will Never, Ever, Mine The Asteroid Belt

Sci-Fi is a totally unreliable guide to reality

Image credit: Smithsonian

Lately Medium has been presenting me with fanboy articles all breathlessly proclaiming that we’re about to launch off into space to mine the asteroid belt. The supposed rationale is that we’re running out of minerals here on Earth so logically (as per the Monty Python definition of the word, at least) we need to spend hundreds of billions of dollars to attempt to mine asteroids.

But for those of us who didn’t waste our youth watching cheap Sci-Fi and who consequently have a useful but sadly uncommon grasp of reality, it’s immediately apparent that the fantasy of mining the asteroid belt is just that: pure fantasy.

This article will explain why.

First of all, despite what countless Hollywood schlock movies and TV shows have depicted, the asteroid belt is nearly empty. Most asteroids are very small, measuring a few tens of meters across. Meanwhile, the average distance between any two small asteroids is nearly one million kilometers (around 590,000 miles). In other words, the average separation between two small asteroids is more than twice the distance between the Earth and the Moon. Would we really, truly, expend vast amounts of money and rocket fuel to travel such enormous distances in order to attempt to harvest mere grams of mineral (at best) from these small chunks of space debris?

If we are delusional and therefore answered “yes” to that question, the next one pops up: how would we know which asteroids to attempt to mine? It’s not like surveyors have been out there and stuck signs on them saying “this one has a mass of 5.7 metric tonnes and contains 62 grams of platinum and 17 grams of cobalt.” Most asteroids seem to be composed of not much we’d care about even if they were presented to us on a plate. So we would likely have to attempt to sample many dozens before finding a single one worth the time and expense of attempting to mine.

But let’s say we’re both delusional and able to raise money from gullible investors with the same facility as a fairground huckster like Elon Musk. We’ve therefore spent billions and wasted many years getting to the asteroid belt and trying to identify a likely candidate for mining. Let’s also say we’re…