Uranus Moon Theory Debated

FortKnox writes "Y! has an interesting article on, what is said to be the most puzzling moon in the solar system, The Uranus moon Miranda. Due to the extreme differences in the textures of the surface, a theory of how it happened came about. The old theory was that the moon was shattered in the early ages of the solar system, but fell back together. But now the theory is in question. Instead of something smashing the surface breaking it, they believe it may have to do with seismic activity. Quite an interesting read."

Comments

Re:Hey, two articles in a row! ;-)

[hubie]

Remember that you can't "lose" gravity. Even when the pieces are separated, if there is nothing else to continually draw them apart they will still want to reassemble through mutual attraction. It is like watching an exploding firework; after the explosion all the pieces are moving with the same center of mass. In the case of the firework the aerodynamic drag on the little pieces as well as wanting to fall back to Earth keeps the little pieces from reassembling. If the firework was exploded in space, if the initial explosion was not large enough to give the pieces enough escape velocity (that is, enough velocity to escape the gravitational attraction from all the other pieces), the firework would eventually fall back together.

It all depends on what the local environment is like. For instance, the rings around the planets (most notably Saturn) are composed of a bunch of material that doesn't seem to want to reassemble (at least on the several hundred year timescales that we have observed it), and it is believed that the shepherd moons provide enough disturbance to keep the ring material in a ring (actually they keep the material from spreading out uniformly; it is the Roche limit that keeps them from clumping).