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Global surface of Venus. The mapping of Venus refers to the process and results of human description of the geological features of the planet Venus.It involves surface radar images of Venus, construction of geological maps, and the identification of stratigraphic units, volumes of rock with a similar age.
The surface of Venus is comparatively flat. When 93% of the topography was mapped by Pioneer Venus Orbiter, scientists found that the total distance from the lowest point to the highest point on the entire surface was about 13 kilometres (8.1 mi), about the same as the vertical distance between the Earth's ocean floor and the higher summits of the Himalayas.
Global topographic map of Venus, with all probe landings marked (red: returned images; with additional black dot: analyzed samples). There have been 46 space missions to the planet Venus (including gravity-assist flybys). Missions to Venus constitute part of the exploration of Venus.
Consequently, Venus transits only occur when an inferior conjunction takes place during some days of June or December, when the orbits of Venus and Earth cross a straight line with the Sun. [189] This results in Venus transiting above Earth in a sequence currently of 8 years, 105.5 years, 8 years and 121.5 years, forming cycles of 243 years.
Geologic time is the timescale used to calculate dates in the planet's geologic history from its origin (currently estimated to have been some 4,600 million years ago) to the present day. Radiometric dating measures the steady decay of radioactive elements in an object to determine its age.
The geology of solar terrestrial planets mainly deals with the geological aspects of the four terrestrial planets of the Solar System – Mercury, Venus, Earth, and Mars – and one terrestrial dwarf planet: Ceres. Earth is the only terrestrial planet known to have an active hydrosphere.
The final major cold spell occurred from 25,000 to 18,000 years ago and is known as the Last Glacial Maximum when the Fenno-Scandinavian ice sheet covered much of northern Europe while the Alpine ice sheet occupied significant parts of central-southern Europe. However, there were several less cold periods after this.
It is sometimes called Earth's "sister planet" due to their similar size, gravity, and bulk composition (Venus is both the closest planet to Earth and the planet closest in size to Earth). The surface of Venus is covered by a dense atmosphere and presents clear evidence of former violent volcanic activity.