In sci.space.policy Henry Spencer wrote:
In article ,
Sander Vesik wrote:
...A close encounter with a planet can split a rubble pile
into a pair of rubble piles, by tidal interaction. (In fact, one of the
points offered in support of the rubble-pile hypothesis is precisely that
we see a suspiciously large number of double asteroids, which ought to be
fairly rare unless there is some specific mechanism that creates them.)

But if you have two piles of rubble orbiting each other, then surely
tidal forces would over time convert these to fuzzy rubble-balls that would
then coalesce into a single body?

Tidal forces within such a system will probably fairly quickly lock the
spin of each rubble ball to their orbit around each other, but the effect
of that on the spacing between them is quasi-random. (For forward spins
it will move them outward, but there's no special tendency for such small
bodies to have forward spins.) And if they're formed by fission of a
single body, they'll probably start out nearly locked anyway, so any
effect will be small.

Once that's happened, only solar tidal effects will change the spacing of
the system, and those will be very slow -- too slow, in an environment
where close planetary encounters happen frequently.

Ah, I see. Thanx.

--
Sander

+++ Out of cheese error +++