> On Mar 5, 2016, at 17:43, Richard Aiken <xxxxxx@gmail.com> wrote:
>
> Just a thought: does this make the satellite a relatively-recent (geologically speaking) capture by the planet? And/or mean that it's in an unstable orbit (destined to eventually either leave or crash into the planet)?

The low prograde orbit implies youth.  Might be low enough for the Roche limit to a concern.

Tidal forces will tend to pull the moon along in its orbit, speeding it up and putting it in a higher orbit (and slowing the planet's rotation).   From the point of view of people on the planet, it will get smaller and the month will get longer.

If the satellite was in a retrograde orbit, those same forces would be slowing it down and dropping its orbit, until it breaks up or impacts the planet. Unless it manages to go Into a tide-lock.