Venus: Earth's Sister Planet . ... Credit Copyright: NASA , Galileo , Copyright Calvin J. Hamilton Explanation: This picture in visible light was taken by the Galileo spacecraft. Venus is very similar to Earth in size and mass - and so is sometimes referred to as Earth's sister planet - but Venus has a quite different climate. Venus' thick clouds and closeness to the Sun (only Mercury is closer) make it the hottest planet - much hotter than the Earth. ... NASA Official: Jay Norris. ...