Olympus Mons levees along their margins (pictured). The cooler, outer margins of the flow solidify, leaving a central trough of molten, flowing lava. Partially collapsed lava tubes are visible as chains of pit craters, and broad lava fans formed by lava emerging from intact, subsurface tubes are also common. In places along the volcano's base, solidified lava flows can be seen spilling out into the surrounding plains, forming broad aprons, and burying the basal escarpment. Crater counts from high-resolution images taken by the Mars Express orbiter in 2004 indicate that lava flows on the northwestern flank of Olympus Mons range in age
Minor planet more are discovered each month. The Minor Planet Center has documented over 188 million observations and 757,626 minor planets, of which 516,386 have orbits known well enough to be assigned permanent official numbers. Of these, 21,264 have official names. , the lowest-numbered unnamed minor planet is , and the highest-numbered named minor planet is 495759 Jandesselberger. There are various broad minor-planet populations: All astronomical bodies in the Solar System need a distinct designation. The naming of minor planets runs through a three-step process. First, a provisional designation is given upon discovery—because the object still may turn out to be a