In article ,
johnhare wrote:
It seems to me that a tide-locked body in a dawn dusk polar
orbit could well have a permanantly dark side...

Mmm, yes, provided the orbit was sun-synchronous -- precesses once around
the primary per primary orbital period -- which requires a rather exact
match between the orbit characteristics and the primary's equatorial
bulge. I can't see that persisting for very long, however; the exact
match is not very stable.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |