This Scientific American article looks at how landings on Mars have gotten more and more precise, shrinking the “landing ellipse” from 300 km × 100 km (Viking) to 7.7 km × 6.6 km (Perseverance), which enables landings in places other than wide undifferentiated plains. Some locales will be still be off-limits for some time: “For instance, scientists cannot propose landing on high-altitude features such as Olympus Mons because the atmosphere overhead is too tenuous to sufficiently slow down a spacecraft. Regions with very rough terrain or steep slopes are also off-limits, even with [Terrain Relative Navigation]. Furthermore, features such as polar ice caps, canyons, lava tubes and sand dunes offer poor prospects for wheeled rovers and would require alternate forms of mobility.”