Why is Venus so hot?

Venus is the hottest planet in the solar system, even though Mercury is closer to the Sun. Sunlight passes through Venus's clouds and heats the surface, which gives off heat as infrared radiation. The dense carbon dioxide atmosphere absorbs this radiation and traps it, so the heat cannot escape.

The atmosphere is so thick that the pressure at the surface is about 90 times that on Earth, similar to being about 900 meters deep in the ocean. Temperatures are almost the same day and night and from the poles to the equator, because the thick air spreads heat around the planet.

A warning about greenhouse gases

Scientists think Venus may once have had oceans. As it warmed, water evaporated, adding more heat-trapping vapor and leading to a runaway greenhouse effect. Studying Venus helps scientists understand how planetary climates change, though Earth is not expected to become like Venus.

Did You Know?

Soviet Venera landers were the first spacecraft to land on Venus and send back data. They survived only about an hour or two in the harsh conditions.