The planet known as Earth's twin is Venus. This comparison arises because both planets are similar in size, composition, and proximity to the Sun; however, their atmospheres and surface conditions are drastically different. Venus has a thick atmosphere rich in carbon dioxide and clouds of sulfuric acid, leading to an extreme greenhouse effect with surface temperatures soaring over 900 degrees Fahrenheit (475 degrees Celsius). Despite these harsh conditions, studying Venus helps scientists understand planetary processes and the evolution of climates, providing insights into potential climate changes that could affect Earth.