Venus and Earth are often described as sister planets, and it is easy to see why. The two planets are similar in size and both are found in the Solar System’s “Goldilocks Zone.” They are both classified as terrestrial planets, having a silicate crust and a metallic core. However, with these similarities notwithstanding, the two planets are extremely unlike. For one, Venus is the Solar System’s hottest planet, with surface temperatures exceeding even those on Mercury, which is closer to the Sun. The planet is also much denser than Earth, 92 times denser to be exact.
The differences between the two planets can also be observed in their respective revolutions and rotations. The Earth’s rotation and revolution are not seen as extraordinary and are used as the yardstick against which those of other planets are measured and analyzed. The revolution of a planet is period a planet uses to go around its star (the Sun). Venus takes 224.65 Earth days to complete one revolution around the Sun, which is also the length of a Venus year. Compared to the Earth’s year, a Venus year is about 0.615 times (61.5%) that of the Earth. Venus revolves around the Sun at a mean distance of 0.72 Astronomical Units (AU) or 67 million miles, having virtually zero eccentricity (about 0.00677), resulting in an almost perfect-circular orbit.
The result of the near-perfect circular orbit of the planet is that the planet has little variation in surface temperatures throughout the year. Unlike on Earth where temperatures vary, creating seasons, Venus experiences similar surface temperatures throughout the planet’s year. The issue is compounded by the low axial tilt of the planet, which at 2.64 degrees is the second-lowest of any planet. In comparison, the Earth has an axial tilt of 23.44 degrees. Therefore, the scorching temperatures on Venus, which average at 462 degrees Celsius, are the same regardless of day or night, or position on the planet; be it on the poles or the equator. Elevation causes the only variation in surface temperatures on the planet.
Venus DayWhile the revolution of Venus around the Sun is remarkable, the planet’s rotation around its axis is extraordinary. For starters, Venus is one of the few planets that has a retrograde rotation where it rotates on its axis in a clockwise direction. Due to Venus’ retrograde rotation, the Sun appears to rise in the west and set on the east, when observed on the planet’s surface. Venus also has the longest rotation period of any planet in the Solar System, lasting 243 Earth days. Therefore, a single year on Venus is made up of 1.92 Venus solar days, meaning in one Venus year, the planet will have experienced only two sunrises/ sunsets. The speed of the planet’s equatorial rotation estimated to be about 4 miles per hour, which is extremely slow when compared to the Earth’s equatorial rotation speed of about 1,038 miles per hour. The extremely slow rotation of Venus has resulted in the planet having a near-perfect spherical shape.