Venus and Earth both share a similar size, gravity and bulk composition and hence, sometimes it is nicknamed as Earth's twin. But with a thick cloak of sulphuric acid clouds and a surface pressure nearly one hundred times that of Earth , makes it less hospitable than Earth. Venus once possessed Earth-like oceans, which evaporated into space to leave a barren landscape.
Venus is a big planet, being heated by radioactive elements in its interior. Some areas in Venus appear to be composed of darker rock , which shows relatively recent volcanic flows.
Both Russia and America sent probes to Venus during the 1970s and 80s – Venera and Pioneer, respectively – that sampled rocks made of basalt. Basalt is formed from cooling lava erupted by volcanoes, and, as is the case on Earth, where magma up-wells along ocean ridges to make new oceanic crust.
The new map of Venus reveals lighter coloured and older rocks with characteristics similar to Earth's granitic continents. Granite is created when basaltic rocks are forced down into the fiery interior of the planet by the process of plate tectonics, which builds and destroys the Earth's crust in an endless cycle. Water combines with the basalt to form granite and the mixture is reborn through volcanic eruptions.
According to the planetary scientists if there is granite in Venus then there must have been ocean in the past.
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