Why a Day on Venus Is Longer Than Its Year

Venus is almost Earth's twin in size, but very little else about it is familiar.

A very slow spin

Venus rotates once every 243 Earth days, but orbits the Sun in about 225 Earth days. Measured against the stars, its day is longer than its year.

And it spins backwards

Venus rotates in the opposite direction to most planets. Combined with its orbit, this means the time from one sunrise to the next — a solar day — is about 117 Earth days. On Venus the Sun rises in the west.

A world of extremes

• Surface temperatures reach about 465 °C — hot enough to melt lead.
• A thick carbon dioxide atmosphere traps heat in a runaway greenhouse effect.
• Clouds of sulphuric acid hide the surface; spacecraft like Magellan mapped it with radar.