The Two Axes of Space Resources

If it were three I'd have to use ternary diagrams

Why does the popular press keep getting hung up again and again on gold asteroids worth trillions of dollars? Are the lunar poles a water-rich oasis, or a desert mirage? Will spatially limited resources lead to conflict? 

I’ll contend these questions and many others can be better understood with a “two-axis approach” to space resources.

Axis 1: Total Abundance

We’ll start with the easier one: Total Abundance. This is exactly what it sounds like and simply considers the total amount of a material of interest. The material could be an individual element (H, Ti, W), a compound or mineral (H2O, CH4, CaSO4), or something more complex (regolith). The only other piece of information needed is the boundary: are we considering a specific region on a planet’s surface, or the entire planet/asteroid, and to what depth beneath the surface? After these are defined it becomes a counting problem to add up the amount of the material within the bounding volume. This will not always be straightforward, but order of magnitude estimates can be reached with the existing planetary sample collection and remote sensing data.

Materials that plot high on the Total Abundance axis are conducive to a post-scarcity condition, while those that plot low on this axis are at risk of being exhausted or at least severely depleted in the relatively near term.

Axis 2: Concentration

The Total Abundance axis tells us how much stuff is out there, but doesn’t say anything about how easy or difficult it will be to actually get that stuff. This is why the Concentration axis is necessary. It’s calculated by dividing the mass of the material of interest (element, compound, etc.) by the total mass of all the stuff present. The concentration can be understood in terms of “thermodynamic rarity”, and on certain planets (mostly Earth), significant geologic processing has taken place over billions of years to counteract entropy and build up concentrated deposits of elements. These processes have happened either to a lesser extent or not at all on other bodies like Mars and the Moon.

Concentration is crucial because in general, the amount of energy (and therefore money) it takes to extract a resource is inversely and exponentially proportional to its concentration. The more other stuff that has to be removed, the more effort it takes. Based on prevailing economic conditions, each type of terrestrial resource has a rough concentration below which it no longer makes sense to extract. When low concentrations become a problem, substitution for other materials is often required, or new technologies are needed to continue extracting at lower and lower concentrations.

Two-axis approach

Now that the two axes are defined, we simply combine them together like so:

 For simplicity, we can divide up the plot into four quadrants that I’ve branded with slightly goofy labels:

The Kardashev quadrant implies significant amounts of energy are available to overcome the difficulty inherent in extracting low-concentration resources. A Type ~1.0 civilization may be needed to access most of the materials that fall in this field.

The Utopic quadrant is the best of both worlds, and is labeled as such because it doesn’t require the high technology and energy levels for the Kardashev region, which may be monopolized and drive inequality. 

In the lower left, the Barren materials are quite hopeless and are unlikely to have much utility as space resources in the future.

And finally, the Opportunist field presents low hanging fruit that are easy to get at, but also easily exhausted. High concentration but low overall abundance usually implies a resource is clustered rather than widespread within a region, such that prospecting is needed. 

Now let’s plot some things up on the graph. No numbers, just rough placement (open to debate). It’s also important to note that different materials are not directly comparable when plotted with actual numbers: for example, the energy to extract iron from a certain concentration of iron ore is not necessarily equal to that needed to extract that same concentration of methane ice from an ultra-cold trap. 

Different forms of the concentration can be plotted, for example the maximum, mean, range, etc.

So, coming back to the opening questions:

1. The popular press gets hung up on trillion-dollar asteroids because they don’t take into account the concentration axis. Low concentrations and high abundances push things up into the Kardashev quadrant, which are not practical in the near term.

2. Water on the Moon is in serious need of ground-based prospecting for polar ice, and I think it could end up plotting anywhere along the bottom half, or potentially into the Kardashev quadrant for things like pyroclastic glasses and solar wind implanted volatiles. In the long term, more of a mirage than an oasis. 

3. Martin Elvis has argued lately that many lunar resources are highly localized and that this will lead to near-term crowding and conflict. I’m not as pessimistic here, because this is only likely to be true for a few things that fall in the Opportunist quadrant, and for most resources, there are better places to go than the Moon (read: Mars) that will push us upwards on the graph, and technology will keep advancing to push us from right to left.

The two axes are a simple approach (perhaps too simple?), but are a useful way to think about problems and avoid some of the pitfalls that plague the space resources field.