Asteroid (16) Psyche – Again! Or Riches Evaporate, Again

Thanks to my latest novel “Spoliation”, I have had to take an interest in asteroid mining. I discussed this in a previous post (https://ianmillerblog.wordpress.com/2020/10/28/asteroid-mining/) in which I mentioned the asteroid (16) Psyche. As I wrote, there were statements saying the asteroid had almost unlimited mineral resources. Initially, it was estimated to have a density (g/cc) of about 7, which would make it more or less solid iron. It should be noted this might well be a consequence of extreme confirmation bias. The standard theory has it that certain asteroids differentiated and had iron cores, then collided and the rock was shattered off, leaving the iron cores. Iron meteorites are allegedly the result of collisions between such cores. If so, it has been estimated there have to be about 75 iron cores floating around out there, and since Psyche had a density so close to that of iron (about 7.87) it must be essentially solid iron. As I wrote in that post, “other papers have published values as low as 1.4 g/cm cubed, and the average value is about 3.5 g/cm cubed”. The latest value is 3.78 + 0.34.

These varied numbers show how difficult it is to make these observations. Density is mass per volume. We determine the volume by considering the size and we can measure the “diameter”, but the target is a very long way away, it is small, so it is difficult to get an accurate “diameter”. The next point is it is not a true sphere, so there are extra “bits” of volume with hills, or “bits missing” with craters. Further, the volume depends on a diameter cubed, so if you make a ten percent error in the “diameter” you have a 30% error overall. The mass has to be estimated from its gravitational effects on something else. That means you have to measure the distance to the asteroid, the distance to the other asteroid, and determine the difference from expected as they pass each other. This difference may be quite tiny. Astronomers are working at the very limit of their equipment.

A quick pause for some silicate chemistry. Apart from granitic/felsic rocks, which are aluminosilicates, most silicates come in two classes of general formula: A – olivines X2SiO4 or B – pyroxenes XSiO3, where X is some mix of divalent metals, usually mainly magnesium or iron (hence their name, mafic, the iron being ferrous). However, calcium is often present. Basically, these elements are the most common metals in the output of a supernova, with magnesium being the most. For olivines, if X is only magnesium, the density for A (forsterite) is 3.27 and for B (enstatite) 3.2. If X is only iron, the density for A (fayalite) is 4.39 and for B (ferrosilite) 4.00. Now we come to further confirmation bias: to maintain the iron content of Psyche, the density is compared to enstatite chondrites, and the difference made up with iron. Another way to maintain the concept of “free iron” is the proposition that the asteroid is made of “porous metal”. How do you make that? A porous rock, like pumice, is made by a volcano spitting out magma with water dissolved in it, and as the pressure drops the water turns to steam. However, you do not get any volatile to dissolve in molten iron.

Another reason to support the iron concept was that the reflectance spectrum was “essentially featureless”. The required features come from specific vibrations, and a metal does not have any. Neither does a rough surface that scatters light. The radar albedo (how bright it is with reflected light) is 0.34, which implies a surface density of 3.5, which is argued to indicate either metal with 50% porosity, or solid silicates (rock). It also means no core is predicted. The “featureless spectrum” was claimed to have an absorption at 3 μm, indicating hydroxyl, which indicates silicate. There is also a signal corresponding to an orthopyroxene. The emissivity indicates a metal content greater than 20% at the surface, but if this were metal, there should be a polarised emission, and that is completely absent. At this point, we should look more closely at what “metal” means. In many cases, while it is used to convey what we would consider as a metal, the actual use includes chemical compounds with a  metallic element. The iron levels may be as iron sulphide, the oxide, or, as what I believe the answer is, the silicate. I think we are looking at the iron content of average rock. Fortune does not await us there.

In short, the evidence is somewhat contradictory, in part because we are using spectroscopy at the limits of its usefulness. NASA intends to send a mission to evaluate the asteroid and we should wait for that data.

But what about iron cored asteroids? We know there are metallic iron meteorites so where did they come from? In my ebook “Planetary Formation and Biogenesis”, I note that the iron meteorites, from isotope dating, are amongst the oldest objects in the solar system, so I argue they were made before the planets, and there were a large number of them, most of which ended up in planetary cores. The meteorites we see, if that is correct, never got accreted, and finally struck a major body for the first time.

Biogenesis: how did life get started?

Early next year I have been invited to give a talk on biogenesis. How life gets started is of interest, because now we know there are a number of planets around other stars, if we know how it can get started, we can know whether life could or should form on a given planet. Of course, nobody actually knows, which has the obvious benefit is that if I get something a little wrong, nobody (including me) will know, and the second one is, one can use logic to cut away a lot of some rather silly stuff being said elsewhere. The most obvious silly suggestion (in my opinion) to me is panspermia, which is when life came from somewhere else, travelled through space on a meteor, and landed on Earth, whereupon the life form flourished in a new environment. Supporters of this theory point out that very primitive life forms can survive in a vacuum, and that DNA has been shown to be able to survive through extended time in vacuum and radiation, if buried inside a rock.

So, what is wrong with this theory? First, let us think about “extended periods of time”. A number of meteorites have been found that originated on Mars, and these have taken millions of years to get here. (Not there has been any sign of viable life on them.) We have no evidence whatsoever that life forms could last that long, nor have we any reason to believe that Mars was a better place for life to get started than here. Had the life come from another solar system, it had to survive for hundreds, or thousands of millions of years, because of the huge distances in space. This also shows another problem: if they take that long to arrive, and there is not that many of them, the concentration of them is very low. Why does it take that long? Basically, because ejecta that escapes Mars goes into orbit around the sun, and stays in that orbit indefinitely until it hits something else. Compared with the size of the solar system, Earth is a tiny microscopic dot. If it comes from another star system, it will arrive with a velocity greater than the escape velocity of our star, so it will come in at extreme velocity and either hit the Earth or never pass it again.

The fact that DNA can survive (although it has hardly been shown to be viable for that length of time) is insufficient to bring life here. Life will contain a set of enzymes, and they get denatured on warming. Yes, there are special enzymes in hot pools, but these have evolved there. Most enzymes denature and then refuse to work if heated half-way to boiling, and a meteorite coming into the Earth’s atmosphere will get a lot hotter than that. But let us suppose it survives and either hits land or water. Now what? A life form has to support itself by consuming what it needs from its environment. It needs a boundary to contain it (skin, in our case), it needs chemicals to replace it, it needs some means of obtaining energy, and it needs chemicals to enable it to use energy. If any of these are missing, then the life form will die.

Energy for life on Earth comes from the sun, via photosynthesis. We know that on Earth life may well have been around in some form or other for something like a billion years before photosynthesis evolved. That means that if the original life forms came from space, they had no means of using solar energy that we know of, hence they would have to rely on chemical processing. There would then be the problem of finding nitrogen-rich organic compounds from which to make things like protein and more nucleic acids. Either those things were around or they were not. If they were not, the life form would die out, as it would be impossible to reproduce. If they were around, then why did they not evolve to form life? Thus any conditions present that would permit an alien life form to grow would also be sufficient for the life form to evolve from what is there. I cannot prove it did, but from Occam’s razor, life coming from outer space is an unnecessary assumption unless there is proof, and since it is sufficient for life to form here if the chemicals required for alien life to survive are here, it is simpler to assume that is what happened. I am convinced we are ourselves, and not some remnants of some space catastrophe.