The planet known for its extreme temperatures is Venus. Often referred to as Earth's "sister planet" due to its similar size and proximity, Venus has a thick atmosphere composed mainly of carbon dioxide, with clouds of sulfuric acid. This dense atmosphere creates a runaway greenhouse effect, resulting in surface temperatures averaging around 467 degrees Celsius (872 degrees Fahrenheit). These extreme temperatures make Venus the hottest planet in the solar system, even more so than Mercury, which is closer to the Sun. The harsh conditions on Venus pose significant challenges for spacecraft and exploration missions attempting to study its geology and atmosphere.