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Terrestrial planets have a compact, rocky surfaces, and Venus, Earth, and Mars each also has an atmosphere. Their size, radius, and density are all similar. Terrestrial planets have numerous similarities to dwarf planets (objects like Pluto), which also have a solid surface, but are primarily composed of icy materials.
Three of the four inner planets (Venus, Earth, and Mars) have atmospheres substantial enough to generate weather; all have impact craters and tectonic surface features, such as rift valleys and volcanoes. [91] Mercury (0.31–0.59 AU from the Sun) [D 6] is the smallest planet in the Solar System.
Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to the Sun: Mercury, Venus, Earth and Mars. Among astronomers who use the geophysical definition of a planet , two or three planetary-mass satellites – Earth's Moon , Io , and sometimes Europa – may also be considered terrestrial planets.
The atmospheres of Mars and Venus are both dominated by carbon dioxide, but differ drastically in density: the average surface pressure of Mars's atmosphere is less than 1% that of Earth's (too low to allow liquid water to exist), [123] while the average surface pressure of Venus's atmosphere is about 92 times that of Earth's. [124]
The global surface of Venus was first mapped by the Magellan orbiter during 1990–1991 with 50 km spatial and 100 m vertical resolution. During three orbit regimes, the surface images were transmitted back to the Earth. These three orbiting motions of the spacecraft are called mapping cycle 1, 2 and 3.
Approximate sizes of the planets relative to each other. Outward from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Jupiter's diameter is about 11 times that of the Earth's and the Sun's diameter is about 10 times Jupiter's. The planets are not shown at the appropriate distance from the Sun.
"Inferior planet" refers to Mercury and Venus, which are closer to the Sun than Earth is. "Superior planet" refers to Mars, Jupiter, Saturn, Uranus, and Neptune (the latter two added later), which are further from the Sun than Earth is. The terms are sometimes used more generally; for example, Earth is an inferior planet relative to Mars.
Geology of Venus. Volcanism on Venus; Physical characteristics of the Earth Figure of the Earth; Structure of the Earth. Earth's crust; Earth's mantle; Earth's outer core; Earth's inner core; Earth's magnetic field; Atmosphere of Earth; Geology of Earth. Lithosphere of Earth. Plate tectonics; Hydrosphere of Earth Water distribution on Earth; Tides