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
Mars mainly phyllosilicates and other minerals known from Mars, point toward an origin of Phobos from material ejected by an impact on Mars that reaccreted in Martian orbit, similar to the prevailing theory for the origin of Earth's moon. Although the VNIR spectra of the moons of Mars resemble those of outer-belt asteroids, the thermal infrared spectra of Phobos are reported to be inconsistent with chondrites of any class. Mars may have moons smaller than in diameter, and a dust ring is predicted to exist between Phobos and Deimos. Dozens of crewless spacecraft, including orbiters, landers, and rovers, have been sent