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Though differing in size and temperature, terrestrial planets of the Solar System were reported to have high Earth Similarity Index values – Mercury, Venus, Earth and Mars. Sizes to scale. The Earth Similarity Index (ESI) is a proposed characterization of how similar a planetary-mass object or natural satellite is to Earth. It was designed to ...
Venus has been the prime example for a planet resembling Earth and how such a planet can differ. An Earth analog, also called an Earth twin or second Earth, is a planet or moon with environmental conditions similar to those found on Earth. The term Earth-like planet is also used, but this term may refer to any terrestrial planet.
The possibility of life on Venus is a subject of interest in astrobiology due to Venus' proximity and similarities to Earth. To date, no definitive evidence has been found of past or present life there. In the early 1960s, studies conducted via spacecraft demonstrated that the current Venusian environment is extreme compared to Earth's.
Venus is similar in size and distance from the sun when compared with Earth, and some researchers believe the planet might have even had an Earth-like climate at some point.
Venus is similar to Earth in size and density, and so probably also in bulk composition, but it does not have a significant magnetic field. [7]: 1729–1730 Earth's magnetic field is produced by what is known as the core dynamo, consisting of an electrically conducting liquid, the nickel-iron outer core that rotates and is convecting.
These similarities, and its proximity, have led Venus to be called Earth's "sister planet". At present it has not been established whether the gravity of Mars, 0.38 times that of the Earth, would be sufficient to avoid bone decalcification and loss of muscle tone experienced by astronauts living in a micro-gravity environment.
Venus is one of the four terrestrial planets in the Solar System, meaning that it is a rocky body like Earth. It is similar to Earth in size and mass and is often described as Earth's "sister" or "twin". [33] Venus is very close to spherical due to its slow rotation. [34]
The Moon is similar, but lacks a substantial iron core. [1] Three of the four solar terrestrial planets (Venus, Earth, and Mars) have substantial atmospheres; all have impact craters and tectonic surface features such as rift valleys and volcanoes.