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The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weather features such as clouds and hazes), all retained by Earth's gravity.
Superior planets: Planets whose orbits lie outside the orbit of Earth. [nb 1] Jupiter, Saturn, Uranus and Neptune: Trojan planet: A planet co-orbiting with another planet. The discovery of a pair of co-orbital exoplanets has been reported, but later retracted. [3] One possibility for the habitable zone is a trojan planet of a gas giant close to ...
Most of Earth's surface is ocean water: 70.8% or 361 million km 2 (139 million sq mi). [97] This vast pool of salty water is often called the world ocean, [98] [99] and makes Earth with its dynamic hydrosphere a water world [100] [101] or ocean world. [102] [103] Indeed, in Earth's early history the ocean may have covered Earth completely. [104]
"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.
Earth's surface is dominated by the ocean, which forms 75% of Earth's surface.. An ocean world, ocean planet or water world is a type of planet or natural satellite that contains a substantial amount of water in the form of oceans, as part of its hydrosphere, either beneath the surface, as subsurface oceans, or on the surface, potentially submerging all dry land.
Water is a basic necessity of life. Since two thirds of the Earth is covered by water, the Earth is also called the blue planet and the watery planet. [notes 1] The hydrosphere plays an important role in the existence of the atmosphere in its present form. Oceans are important in this regard.
The Greek philosopher Empedocles (c. 450 BC) was the first to propose the four classical elements as a set: fire, earth, air, and water. [9] He called them the four "roots" (ῥιζώματα, rhizōmata). Empedocles also proved (at least to his own satisfaction) that air was a separate substance by observing that a bucket inverted in water did ...
Second, a planet with a larger mass tends to have more gravity, so the escape velocity tends to be greater, and fewer particles will gain the energy required to escape. This is why the gas giant planets still retain significant amounts of hydrogen, which escape more readily from Earth's atmosphere. Finally, the distance a planet orbits from a ...