Damian Coffey writes:

> Jim Phillips wrote:
>
>  > 43. In Gulliver's Travels Jonathan Swift described the two moons of Mars,
>  > Phobos and Deimos, giving their exact size and speeds of rotation. He did
>  > this more than 100 years before either moon was discovered.
>
>  At least according to Kim Stanley Robinson (Green Mars) this was a lucky
>  guess...  The reasoning went as follows:
>
>  - Venus has 0 moons, Earth has 1, Jupiter has 4, so Mars probably has 2.
>  - We can't see them, so they are probably small and close to the surface
>  of the planet.
>  - If they are close to the surface, then they must be fast.
>
>  Quite well reasoned, but at the same time, a lucky guess.

There are some good books on Mars that have been put up in their entirety on
the web. One of them is "The Planet Mars." The relevant section that adds a
bit more to Damian's comments is:

    http://www.uapress.arizona.edu/online.bks/mars/chap14.htm

Wirt Atmar