Editing Hadean Eon (section)

==== Venus ====
Early in its history, <u>Venus</u> underwent differentiation into a core, mantle, and crust, similar to other terrestrial planets. However, the specifics of Venus' differentiation might have been influenced by its size, composition, and the solar environment, leading to a planet that today lacks a global intrinsic magnetic field. This absence is possibly due to a slower rotation rate or differences in its core's composition or thermal dynamics. Venus' thick atmosphere, primarily composed of carbon dioxide with clouds of sulfuric acid, is likely a result of volcanic '''outgassing'''. The planet shows evidence of extensive volcanic activity in its past, which would have released large amounts of CO2 into the atmosphere. Unlike <u>Earth</u>, Venus lacks plate tectonics and significant surface water, mechanisms that on Earth recycle carbon dioxide back into the planet's interior. The inability to remove CO2 from the atmosphere led to a runaway '''greenhouse effect''' on Venus; it trapped solar radiation and dramatically increased surface temperatures, leading to conditions that evaporated any liquid water that may have existed, further exacerbating the greenhouse effect.

Though Venus does not have plate tectonics like Earth, there is evidence of tectonic activity, such as '''folding''' and '''faulting''', likely driven by mantle plumes and volcanic upwelling. This tectonic activity contributes to the creation of features like '''coronae''' and '''tesserae''', which are unique to Venus and indicate a complex interplay of crustal deformation and volcanic activity. The extreme surface temperatures and high atmospheric pressure on Venus could contribute to the crust being too soft for significant fracturing into plates and could inhibit '''subduction''', a key process in plate tectonics. Venus' lithosphere may be more rigid and thicker than <u>Earth's</u>, possibly due to its high surface temperatures. This rigidity can prevent the '''lithosphere''' from breaking into plates and moving over the mantle.

Differences in mantle temperature and the style of mantle convection may also play a role; Venus' mantle convection might occur in a <u>single-layer regime</u>, unlike the Earth's <u>multi-layer convection</u>, which is crucial for plate tectonics. Water acts as a '''lubricant''' for subduction on Earth, and the relative dryness of Venus' mantle compared to Earth's might hinder the development of plate tectonics. Venus' lack of surface water could mean that its lithosphere does not have the same level of '''plasticity''' required for plate movements.

One of the most intriguing aspects of Venus is its '''superrotating''' atmosphere, where the upper atmosphere circulates around the planet much faster than the planet itself rotates. This phenomenon is thought to be driven by solar heating and complex interactions between the planet's surface and atmosphere. The atmospheric conditions on Venus during the Hadean or its equivalent early history would have been drastically different from today, however. The early atmosphere of Venus, like that of the other terrestrial planets, was likely influenced by volcanic outgassing, comet impacts, and the composition of the solar nebula from which it formed. Over time, Venus evolved under the runaway greenhouse effect, leading to the extremely dense, CO2-rich atmosphere we observe today. This process increased surface temperatures to the current average of about 467°C (872°F), creating a thick atmosphere dominated by carbon dioxide with clouds of sulfuric acid.