the Moon

The column about “Why does the same side of the moon always face the earth?” says that “captured” or “synchronous” rotation…[is] common throughout the solar system.

How common is it? Of all the moons that we can see clearly enough to detect their rotation, what percentage do not appear to rotate when viewed from the surface of the planet?

Most of the astronomy pages I found use the same word Cecil did, “most”. In particular, the following page on Saturn,, says 16 of Saturn’s 18 positively identified moons are synchronous. says all 16 of Jupiter’s moons are synchronous. And makes the bold claim that All the satellites of the outer planets with radii > 200 km are in synchronous rotation with respect to their host planet

Interesting info on planets that cannot support life and have a big advantage in gravitational pull. If you only consider the smaller, inner planets (acknowledging that Mercury could never support life and Venus can’t with it’s present atmosphere), do their residents gaze on static or rotating moons?

well, as neither Mercury nor Venus have companion bodies, it is kinda hard to tell. I don’t know about the puny rocks Mars captured, but as the Moon is the only satellite in the inner system of any appreciable size I would say the statement is confirmed and valid.

About Mars–this link reports Phobos to be synchronous, I’m not sure about the other moon, but I would guess it is too. In any event, the Martian moons are so small they just look like bright stars from the planet surface.

The reference about Mars actually said:
“They have nearly circular, equatorial orbits, and their rotations are locked to their orbital motions, so that each always turns the same face to Mars, as the Moon does to Earth.”

Statistically, that about clinches it. I’m forced to conclude that any other “intelligent” beings on other planets probably gaze at a flat, static, plate-like moon(s) over their planet. This means that they probably developed their own version of the “flat Earth” theory.