Venus is often called Earth's "sister planet" because of their similarities in size, mass, and composition. Both are rocky worlds that formed about the same time in the inner solar system; however, despite these similarities, Venus evolved into a world vastly different from Earth, with surface temperatures around 465°C, crushing atmospheric pressure 90 times greater than Earth's and thick clouds containing sulfuric acid circling the planet. These dramatic differences between two such similar planets make Venus a fascinating subject for planetary scientists to study.