*appears to experience vibrations*strong enough to create fresh surface material."

Vibrations usually are not of high enough amplitude to be visually seen optically except under special circumstances, unless driven by rather large forces, or resonances which amplify initially small force inputs. I have not heard of anyone's having planted seismometers on near-Earth asteroids.

**Gravity is a force without large oscillations**, itself, so "seismic shaking due to gravity" seems a very dubious explanation. Does Dr. Benzel have photos or spectral data changes showing the appearance of new material on asteroids?

One effect of gravity is tidal action due to differences in the force of gravity from an external body on radially opposite sides of a body. Taking an asteroid which is, say, 300 meters across (example only) at 16 Earth radii out at closest approach, what is the difference in the force of gravity on the nearest and farthest surfaces of the (spherical) asteroid?

A quick calculation at 16R ± 150m shows that the force of gravity

*differs*by only 0.000000225 m/s² between these two distances, the two sides of the asteroid. (This is not very much, in case you are asking yourself if it is significant.) in terms of Earth's gravity at its nominal surface, where we are in a 1 gee acceleration, this represents a difference of 1 over 43,541,163 gee. A constant force differential of one forty three millionth of a gee is not going to cause seismic shaking and new material to come spouting out or tumbling down from a stony asteroid. At least I'd bet. And what did Dr. Binzel put into his model, assuming that is what he was working with, a mathematical construct like mine on Excel, which would reveal radial "shaking". Springs? The asteroid isn't coming off its tracks from this steady, tiny force difference. Earth's gravity is not taking the tiny asteroid by the scruff of its swollen little neck and shaking it back and forth.

I think Dr. B. is blowing smoke, or else he says "shaking" but doesn't actually, precisely

*mean*"shaking".

Jim