Diamonds in the Sky

Looks like some of those constant width shapes that look like they shouldn't roll smoothly.

Very interesting. Thanks. I was unable to find a definition for YORP, as used in this article.

Hope these help.
Was curious as well...because in Australian Yorp, or Y'reup means get another round of beers which I guess could explain the wobbly orbits ... but -
"The Yarkovsky–O'Keefe–Radzievskii–Paddack effect, or YORP effect for short, changes the rotation state of a small astronomical body – that is, the body's spin rate and the obliquity of its pole – due to the scattering of solar radiation off its surface and the emission of its own thermal radiation."

https://www.planetary.org/articles/20141211-the-yorp-effect-and-bennu

https://en.wikipedia.org/wiki/Yarkovsky%E2%80%93O%27Keefe%E2%80%93Radzievskii%E2%80%93Paddack_effect

Thanks!

On another note, shouldn't a very diffuse gas cloud exist around each of these rubble piles? The gas pressure level would certainly be less than the best vacuum levels found on Earth. But shouldn't the gas pressure level be higher than interplanetary space? I have no idea how one might measure this.

If the gas atoms or molecules at the ambient temperature have a greater velocity than the escape velocity (0.5 - .74 km/hr for Bennu, 30 cm/s for Ryugu) then they wouldn't stick around. The molecular velocity decreases as molecular mass increases as shown below for room temperature.

Molecular Velocities and Kinetic Energy | Gases (nigerianscholars.com)

By the Numbers | 101955 Bennu – NASA Solar System Exploration

Resurfacing processes on asteroid (162173) Ryugu caused by an artificial impact of Hayabusa2's Small Carry-on Impactor - ScienceDirect

There would have to be a source for this gas, or it would disappear in a very short time just as a mud puddle dries up. The very weak gravity would not hold on to it.

I believe the average (ambient) and peak temperatures for both of these rubble piles are considerably less than 25°C. So my supposition of a gas cloud around these objects seems plausible.