Moons of Mars its 30-hour orbit, it takes 2.7 days to set in the west as it slowly falls behind the rotation of Mars. Both moons are tidally locked, always presenting the same face towards Mars. Since Phobos orbits Mars faster than the planet itself rotates, tidal forces are slowly but steadily decreasing its orbital radius. At some point in the future, when it approaches Mars closely enough (see Roche limit), Phobos will be broken up by these tidal forces. Several strings of craters on the Martian surface, inclined further from the equator the older they are, suggest that there may have been
The Planet of Doubt The Planet of Doubt "The Planet of Doubt" is a science fiction short story by Stanley G. Weinbaum that was first published in the October 1935 issue of "Astounding Stories". It is Weinbaum's third story featuring Hamilton Hammond and Patricia Burlingame, a sequel to "Parasite Planet" and "The Lotus Eaters". Following his expedition to the night side of Venus, the Smithsonian Institution appoints Hamilton "Ham" Hammond to head an expedition to Uranus. In Weinbaum's version of the Solar System, all of the gas giants generate significant amounts of infrared radiation, enough to produce Earthlike environments on the inner moons of