On looking at 10 Hygieaiaeiea - its orthography is more art than science - I found a couple facts of some interest (to me). One is that, at the 3.14 AU semimajor it is at, it's unstable. Jupiter and Saturn are pulling its orbit to cross Kirkwood's 2:1 gap at 3.279 AU. There's a Lyapunov ("Lhapunov" in Portuguese, I guess) exponent which, flipped, offers a time-value, here thirty millennia (assuming its aphelion hasn't crashed a Hilda or something). After that, even Newton can't tell you.
[SOURCE 8/30: Nesvorný-Morbidelli.]
Which begs the question how 10 H got down here in the first place. It's of a piece with other Ceroids from past Jupiter. More, it shares its orbit with so many other icy sootballs, that Wikipedia thinks it got struck by something. Some of those sootballs will be accidental coörbitals - icy sootballs don't melt at 3.14 AU and some look too large to be divots - but not all. I should add the suspicions that 10-H is orbiting Uranically, on its side and backward.
How long ago was 10-H hit... and where? I find a few models of Jupiter and Saturn being nonresonant as of 2020. Notwithstanding Velikovsky this didn't happen yesterday. The asteroids if truly of 10-H origin would have separated two billion years ago(!). That, I think, constrains when Ceres arrived since Ceres is interior to 10-H. The tacking of Jupiter and Saturn would have ended long before then but, still, two gigayears is a long time.
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