Olympus Mons and hence lead to the low gradients on the surface of the planet. Olympus Mons is an unlikely landing location for automated space probes in the near future. The high elevations preclude parachute-assisted landings because the atmosphere is insufficiently dense to slow the spacecraft down. Moreover, Olympus Mons stands in one of the dustiest regions of Mars. A mantle of fine dust obscures the underlying bedrock, possibly making rock samples hard to come by and likely posing a significant obstacle for rovers. Olympus Mons is the result of many thousands of highly fluid, basaltic lava flows that poured from volcanic
Fictional planets of the Solar System fragments of a single planet was gradually abandoned over the course of the middle decades of the 20th century in favor of the conclusion that no planet had ever accreted in the region of the asteroid belt in the first place. In fiction, various other names were given to the same or similar concepts. Fictional planets in our Solar System beyond the orbit of Neptune have been employed many times as settings or references in science fiction. Following the general reception of Pluto as the ninth planet of the Solar System in 1930, a hypothetical additional planet was sometimes called