[Genesis defender]

Almost all books I read as a kid said that Phobos and Deimos were both just captured asteroids, mostly because they looked lumpy and pock-marked like other asteroids.

[far sider]

Almost all books I read as a kid said that Phobos and Deimos were both just captured asteroids, mostly because they looked lumpy and pock-marked like other asteroids.

That's the problem. If they were captured asteroids they should have elliptical orbits. Phobos and Deimos have nearly circular orbits like Earth's Moon.

[jlogajan]

Almost all books I read as a kid said that Phobos and Deimos were both just captured asteroids, mostly because they looked lumpy and pock-marked like other asteroids.

Circular orbit is tough to acheive in a gravity capture.

[D Rider]

I read books as a kid too.

How about this: "They have likewise discovered two lesser stars, or satellites, which resolve around Mars, whereof the innermost is distant from the center of the primary planet exactly three of his diameters, and the outtermost five; the former revolves in the space of ten hours, and the latter in twenty-one and a half; so that the squares of their periodical times are very near in the same proportion with the cubes of their distance from the center of Mars, which evidently shows they to be goverened by the same law of gravitation that influence other heavenly bodies." -A VOYAGE TO LAPUTA, GULLIVERS TRAVELS, 1726

This discription is within 20% accurate, but the moons were not discovered until 1877 when a powerful enough telescope was created. The moons of Mars have the lowest index of reflectivity of any bodies that we know of in the solar system(almost black). They are also so small, that to be seen from earth by the naked eye, Mars would have to appear in the sky 50 times larger than our moon.

Explain that!