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It was once expected that any icy body larger than approximately 200 km in radius was likely to be in hydrostatic equilibrium (HE). [7] However, Ceres (r = 470 km) is the smallest body for which detailed measurements are consistent with hydrostatic equilibrium, [ 8 ] whereas Iapetus (r = 735 km) is the largest icy body that has been found to ...
Craters larger than roughly 50 km are named for deceased scientists and writers and others who have contributed to the study of Mars. Smaller craters are named for towns and villages of the world with populations of less than 100,000. Large valleys are named for the word "Mars" or "star" in various languages; smaller valleys are named for rivers.
Among the highest nonvolcanic peaks on Mars, formed by the Hellas impact: Aeolis Mons ("Mount Sharp") 4.5 to 5.5 km (2.8 to 3.4 mi) [29] [n 7] 0.16: deposition and erosion [n 8] Formed from deposits in Gale crater; [34] the MSL rover has been ascending it since November 2014. [35] Vesta: Rheasilvia central peak
Most of the larger moons orbit their planets in prograde direction, matching the direction of planetary rotation; Neptune's moon Triton is the largest to orbit in the opposite, retrograde manner. [50] Most larger objects rotate around their own axes in the prograde direction relative to their orbit, though the rotation of Venus is retrograde. [51]
The magnetosphere can be much larger than the planet itself. In contrast, non-magnetized planets have only small magnetospheres induced by interaction of the ionosphere with the solar wind, which cannot effectively protect the planet. [137] Of the eight planets in the Solar System, only Venus and Mars lack such a magnetic field. [137]
A type of exoplanet with a mass only a few times larger than Earth's but with a radius larger than that of Neptune, giving it a very low mean density. Kepler-51b, c and d: Silicate planet: A terrestrial planet that is composed primarily of silicate rocks. All four inner planets in the Solar System are silicon-based. Mercury, Venus, Earth and Mars
The Sun, planets, moons and dwarf planets (true color, size to scale, distances not to scale). The following outline is provided as an overview of and topical guide to the Solar System:
Mars comes closer to Earth more than any other planet save Venus at its nearest—56 million km is the closest distance between Mars and Earth, whereas the closest Venus comes to Earth is 40 million km. Mars comes closest to Earth every other year, around the time of its opposition, when Earth is sweeping between the Sun and Mars. Extra-close ...