Curiosity 1 of 10
1. A day on Venus lasts longer than a year on Venus
Venus takes 243 Earth days to spin once on its axis, and only 225 to orbit the Sun. The planet rotates so slowly that its year ends before a full rotation is complete.
A planet that spins slowly and backwards
On Earth, one rotation takes about 24 hours, and one orbit around the Sun takes 365 days. On Venus, the proportion is reversed: its rotation is so slow that it takes longer than its own orbit.
Venus also rotates in the opposite direction to most planets. For someone on the surface, the Sun would rise in the west and set in the east. Because the rotation and the orbit combine, the interval between one sunrise and the next there is about 117 Earth days.
No one knows for certain why Venus spins this way. Among the hypotheses are a giant collision in the past and the effect, over billions of years, of its very dense atmosphere and the tides caused by the Sun.
The atmosphere, moreover, makes Venus the hottest planet in the Solar System, even hotter than Mercury, which is closer to the Sun. Carbon dioxide traps the heat, and the surface exceeds 460 °C, hot enough to melt lead.
Did you know? Venus is the brightest object in the night sky after the Moon. Because it appears at dusk or before dawn, it became known as the morning star, although it is a planet.
About this list: these are 10 curiosities about space, one per page, with an explanation of each and an extra detail in the "Did you know?" box. The rounded figures follow the most cited measurements; the sources are at the end of the list.
