The planet known as Earth's twin is Venus. This title is attributed to Venus's similar size and composition to Earth, making them relatively comparable in structure. Venus has roughly the same diameter as Earth but has a very different atmosphere, consisting mainly of carbon dioxide with thick clouds of sulfuric acid, resulting in a greenhouse effect that raises surface temperatures to over 450 degrees Celsius (842 degrees Fahrenheit). While both planets share a similar mass and proximity to the Sun, their climates and surface conditions differ vastly.