A Princess of Mars Lowell published two more books, further developing the concept of a dying Mars. Burroughs was aware of these theories and appears to have consciously followed them. However, Burroughs does not seem to have based his vision of Mars on precise reading of Lowell's theories, as there are a number of errors in his interpretation which suggest he may have got most of his information from reading newspaper articles and other popular accounts of Lowell's Mars. The ideas of canals with flowing water and an inhabited, if dying world, were later disproved by more accurate observation of the planet, and fly-bys
Double planet that this definition of double planet depends on the pair's distance from the Sun. If the Earth–Moon system happened to orbit farther away from the Sun than it does now, then Earth would win the tug of war. For example, at the orbit of Mars, the Moon's tug-of-war value would be 1.05. Also, several tiny moons discovered since Asimov's proposal would qualify as double planets by this argument. Neptune's small outer moons Neso and Psamathe, for example, have tug-of-war values of 0.42 and 0.44, less than that of Earth's Moon. Yet their masses are tiny compared to Neptune's, with an