This one’s big, and by that I don’t mean “Ceres.”
Pamerleau, I. F. Sori, M. M. Scully, J. E. C. An ancient and impure frozen ocean on Ceres implied by its ice-rich crust, Nature Astronomy 18 Sep 2024 s41550-024-02350-4
First things first, Nature- not a bunch of amateurs playing around.
The Dawn spacecraft went into orbit around Ceres, the largest asteroid. Even prior, telescopes had detected signs of water loss (activity) at the body- there was a faint, hydrous “atmosphere” seen sometimes. Even as the spacecraft approached, bright spots (faculae) were obvious; we now know those bright spots are the salt deposits left when Ceres water had reached the surface, and evaporated. Clearly, there’s water to be studied; it’s a question of when (historical, or today?), where (poles only, or everywhere? deep, or just under a surface cover?), and how (literal imaging, spectroscopy and in different bands, morphology, gravimetry, or who knows).
And yet, the question of Ceres water is still not settled to this day. It looks like there’s ice under (not on) the surface… but in detail, there’s not much more that can be said confidently. The spacecraft, built to budget and already past schedule, could have had another instrument or two to add to its conclusions and sigma levels. At best, the neutron instrument gave a pretty clear signal of hydrogen, but that includes organics too. But for one thing, the visible camera (FC) showed that the Cererean surface took and retained craters somewhat, which means it has mechanical strength. If Ceres was a ball of ice, craters would slump back to their original level, as they do on Europa, Ganymede, etc. Yet only the largest craters (approaching the scale of Ceres itself) were truly leveled out; plenty of medium and small craters had traditional, bowl-shaped morphology.
Pamerleau et al. now add another dimension. Using material properties, they show certain mixtures of rock and ice explain the surface morphology of Ceres- ice-rich, yet still very firm and able to hold shape. All in all, the near surface could be perhaps 90% ice content, and not lose its craters. It’s the deep interior that can’t be a glacier. If there was a mantle of ice, things would flow back again, and we’d see a different surface than we see (that is, contradictory evidence).
Water: it’s everywhere. And for the Main Belt, both Ceres and Vesta– the two largest asteroids, representing a majority of the Belt’s mass- are hydrated bodies, ripe for mining.