Spheres on Mars

Obviously the spheres are fallen shotgun pellets. "There's another probe, RYllx! Get it!"

OK, seriously, these things do look rather odd. Of the 23 spheres (not counting one partly out of the picture), 11 have pretty clear boundaries between hemispheres--and several of the irregular ones may also, but I can't tell without turning them over to see. That sounds a lot like droplets hardening as they fly. 5 of them have divots--maybe expanding gas explosions?

I'd expect droplets to be squashed more by air pressure, but then the Martian atmosphere is thinner, so maybe this is OK. But in that case do the drops cool fast enough?

And what would be the ratio of melted to blasted material? If this was from a volcanic eruption, I'd expect the rubble of the old hardened cap to be blasted away as well. But I remember pictures of Pompeii showing 10 meter layers of volcanic ash, so maybe we can neglect the old crud. But a lot of that was hot ash, which I was given to understand forms when dissolved gases in the magma expand as the pressure is released. The difference in pressure between subterranean magma and earth's air vs vacuum seems pretty trivial (200-300 MPa or so). So maybe the Martian magma has less dissolved gas? That could be because the pressure is lower (75-120 MPa) or because the chemistry is different. On Earth dissolved gases include SO2, H2O, and CO2 (SO2 is easier to measure than the others, natch). The rovers are seeing rocks with sulfer...

Suppose the beads are from a meteor impact. Then I expect most of the material to be shattered but unmelted rock: if you have enough energy to melt rock, nearby you have enough energy to shatter it, and there's more matter around the melted zone than in it. So unless the melted rock beads travel farther than ordinary gravel, there should be more gravel than beads lying around. I don't see that. So I'd guess this isn't from meteor impacts. Unless . . .

Correction Oops. I forgot that the hotter central stuff will also have more KE, and has a better chance of travelling a long distance.

Is there a systematic bias due to the blowing soil? Will irregular gravel tend to be buried and smoother stuff remain uncovered? It does appear that the more irregular stuff is both smaller and more buried, but I'd want to look at a few more samples, and try a wind tunnel test or two.