Venus

Venus is a rocky planet shrouded in a thick, impenetrable yellowish-white cloud cover that hides its surface from visible light. The planet’s dense atmosphere consists mostly of carbon dioxide, about 3.5 per cent nitrogen, and a small amount of sulfur dioxide—the latter as a corrosive sulfuric acid mist. This atmosphere acts as an extreme greenhouse, preventing heat from escaping. Venus is therefore the hottest planet in the Solar System, with a stable surface temperature of around 465 °C—hot enough to melt lead and make the ground glow in the dark. In addition, atmospheric pressure at the surface is as much as 93 times greater than at sea level on Earth.

Nevertheless, we know a great deal about the surface. In the early 1990s, the Magellan space probe mapped the planet using radar and revealed a dramatic landscape of plains, mountains, meteorite craters, and more than a thousand volcanic structures. In recent years, scientists have found concrete evidence that some of these volcanoes are still active today. Venus is the planet that can come closest to Earth, and it is the brightest object in the sky after the Sun and the Moon. Along with Mercury, Venus is also one of the only planets in the Solar System with no moons of its own.

Although conditions on the surface are extremely inhospitable, conditions are very different 50 kilometres up in the atmosphere. Winds there rage at speeds of up to 360 km/h, but the temperature (30–70 °C) and air pressure resemble those at Earth’s surface. Scientists have even speculated that mysterious dark streaks in the clouds, which absorb ultraviolet radiation, could theoretically be caused by acid-tolerant microbes or bacteria.

Venus has an average distance from the Sun of 108 million kilometres. Spending a day there would be disorienting: the planet rotates extremely slowly and in the opposite direction to most other planets, meaning that the Sun rises in the west and sets in the east. One full day lasts 243 Earth days, which is actually longer than a Venusian year of 225 Earth days. Why the planet rotates “the wrong way” remains a mystery. Perhaps it is the result of a giant collision with another celestial body during the early history of the planetary system. Since its axial tilt is only three degrees, Venus also has no noticeable seasons.