Venus – Venus, Terrestrial Planets, Inner Planets – Venus is the second planet from the Sun and is often referred to as Earth's twin due to its similar size and composition. However, its thick carbon dioxide-rich atmosphere creates a runaway greenhouse effect, making it the hottest planet in the Solar System with surface temperatures reaching 467°C (872°F)—hot enough to melt lead. Venus' dense atmosphere, composed of 96.5% carbon dioxide and clouds of sulfuric acid, results in an atmospheric pressure 92 times greater than Earth's, equivalent to being 900 meters underwater. The planet has a retrograde rotation, meaning it spins in the opposite direction of most planets, taking 243 Earth days to complete one rotation, making its day longer than its 225-day orbit around the Sun. Venus' volcanic surface is covered with lava plains, shield volcanoes, and unique pancake domes, with recent data suggesting active volcanism. The planet was first explored by NASA's Mariner 2 (1962), the first successful interplanetary mission, followed by the Soviet Venera missions (1961–1984), which landed probes on Venus and sent back the first images from its surface before being crushed by the extreme pressure. NASA's Magellan (1989–1994) mapped 98% of the planet's surface using radar, revealing widespread volcanic and tectonic features. More recently, ESA's Venus Express (2005-2014) and JAXA's Akatsuki (2010-present) have studied its atmosphere and weather patterns, including super-rotating winds and polar vortices. Upcoming missions like NASA's DAVINCI+ and VERITAS (2029-2031) and ESA's EnVision (2030s) aim to investigate Venus' geology, atmosphere, and possible past habitability, shedding light on why it evolved so differently from Earth.