Move over Ceres! There's a new, smaller dwarf planet in town called Hygiea

There may be a new dinky dwarf planet that’s even tinier than Ceres, the largest object in the main asteroid belt that currently holds the title as the smallest dwarf planet in our Solar System. Known as Hygiea, after the Greek goddess of health and cleanliness, the object was first discovered in 1849. The rock, measuring just …

[Pascal Monett]

"its surface only had two meager craters"

Yeah, well its size is minuscule and it is far, far out there. There's a good chance that most meteorites missed it and went on to hit the Moon - or Jupiter.

Nonetheless, great science !

[A Non e-mouse]

Re: "its surface only had two meager craters"

The argument is that there should have been a lot of debris in the area so Hygiea should have had more impact craters.

The unwritten alternative is that there are/were processes on Hygiea that have remodeled its surface.

[Tom 7]

Re: "its surface only had two meager craters"

Why more impact craters? Its gravity wont be enough to attract anything with enough speed to make an impact and most of the debris near it would be moving in a similar orbit. Anything moving fast enough to make much of an impact crater would be more likely to kick it out of its orbit or destroy it completely.

[Bill Gray]

Re: "its surface only had two meager craters"

..."Its gravity won't be enough to attract anything with enough speed to make an impact..."

Doesn't matter much. Most of the energy of an impact is due to the difference between your orbit and that of the impactor. And no, orbits are not all _that_ similar for varying main belt objects; they usually go past each other at a few kilometers a second.

"...Anything moving fast enough to make much of an impact crater would be more likely to kick it out of its orbit or destroy it completely."

Again, no. Hygeia is about 430 km across. It'd take a big rock to break it into bits, even at a kilometer or two a second. For every big rock like that, you'd have plenty of smaller ones, and they'd make impact craters.

Hygiea is only slightly further out in the main asteroid belt than Ceres or Vesta. Those have plenty of craters. There's no immediate reason to think this wouldn't have a similar level of cratering.

[annodomini2]

Re: "its surface only had two meager craters"

Formed relatively recently from 2 relatively equal mass bodies with sufficient energy to break the 2 apart and melt them, but not enough to fully disperse the material that they cannot recombine?

[Anonymous Coward]

Looks like..

A lost golf ball belonging to one of the gods.

Caddy!

;-)

[Anonymous Coward]

Death star mk.II

Upgraded Death Star - two craters -> two super-lasers.

[james 68]

Eh?

Looks more sort of 'potatoish' rather than spherical. Either way, solar systems largest potato or solar systems smallest dwarf planet, still one for the books.

[Tom 7]

Re: Eh?

Is the Asteroid World Cup on at the moment?

[ThatOne]

Astonishing it managed to achieve hydrostatic equilibrium at such a tiny size (Vesta is bigger and didn't). Must be made out of marshmallow...

[tojb]

Carbon-rich: role of VDW forces instead of gravity

As a C-type (soot and hydrocarbons) body, Hygiea could be stabilised by collective quantum dispersion forces acting at a level comparable to the tiny gravitational force associated with such a small thing.

https://arxiv.org/abs/1002.2478

On earth it is often a massive ball-ache when powders spontaneously clump and jam, the physics behind the whole thing is quite finely balanced and tricky.

https://powderreg.com/en/home-2/

[Dvon of Edzore]

Re: Carbon-rich: role of VDW forces instead of gravity

So it's not dustless like its namesake?

DIXON-TICONDEROGA-COMPANY-HYGIEIA-DUSTLESS

[tojb]

Re: Carbon-rich: role of VDW forces instead of gravity

apparently