[X] My Assistant

[Phil Stooke]

The best set of grooves on any object since Phobos. This has to put an end to the 'grooves caused by Mars ejecta' argument. fantastic object and a wonderful data set. And this is just the highest priority data, all the rest still to come.

Phil

[bk_2]

The best set of grooves on any object since Phobos. This has to put an end to the 'grooves caused by Mars ejecta' argument. fantastic object and a wonderful data set. And this is just the highest priority data, all the rest still to come.

Phil

The similarities with Phobos are striking, the photos clearly show two families of roughly parallel grooves, in two different planes. But the grooves seem to have been obliterated over most of the surface by later big impacts.

Once again I have to say they look like the tracks of intersection with rings, edge on. What else could carve a long smooth trench on the surface of a large object in space? Where Lutetia might have encountered rings is not going to be easy to answer, the chaos of the early Solar System is way beyond our scrutiny. The grooves do seem to be very old features, pockmarked with small craters, as well as restricted to areas clear of debris from the big ones.

[bk_2]

I will try to get hold of The New Solar System. Thanks for the leads on the mechanisms for ring decay.

I'm skeptical about the idea of decaying rings being the origin of the grooves. How could a decaying ring leave a family of grooves, parallel but separated by gaps many times the width of a groove? These are most apparent on Phobos, but Lutetia has them as well. If the ring orbits the center of gravity and decays onto the surface of a non-rotating body, it would leave a single groove all the way around. If the main body was rotating, and the ring was at high inclination to the equator, the groove would be smeared out. I can't see a mechanism for the creation of families of grooves, which in the case of Phobos, peter out on one hemisphere.