Planet Venus spins so slowly on its axis that one day on the planet lasts nearly 243 Earth days. Deimos orbits Mars in 30 hours. A day on Venus lasts for 243 Earth days or 5,832 hours! Yikes! In addition, Earth has a mass that is 10 times greater.

Compare the Sizes of Mars, Earth, and Moons One year on Mars is about 687 earth days compared to the the 365 days in a year on Earth.

• As a result of Mars being situated further away from the Sun than the Earth, Mars is considered to be cooler than the Earth. So, the day is actually longer than a year, which means that Venus residents would only get to see two sunrises per year. The Martian year is also longer than that of the Earth because it takes Mars longer to orbit the sun. As a result, Mars has seasons like the Earth, though on Mars they are about twice as long given its longer year.

In other words, the period Mars takes to go round the Sun is greater than the period Earth takes to go round the Sun.

As Mars orbits the Sun, it completes one rotation every 24.6 hours, which is very similar to one day on Earth (23.9 hours). A year on Mars lasts 669.6 sols, which is the same as 687 Earth days.

Mars passed its perihelion in June 2007 and its aphelion in May 2008. Their names mean “fear” and “dread”. Phobos and Deimos: The tiny moons of Mars. Phobos orbits Mars in just 7 hours. That’s less than one Earth day! The Moon orbits Earth one time each month. At proper scale, they would be even smaller than the dots shown.

Because it's closer to the Sun than Earth is, the planet has a 225-day year. One Martian sol is about 24.63 hours, while an Earth day clocks in at 23.94 hours. The diameter of Mars is about 6,786 kilometers (4,217 miles), compared to that of Earth, which is about 12,756 kilometers (7,926 miles). • Earth takes 365 days to go around the Sun. A day on Earth is 23.943 hours.

Venus also rotates backwards compared to the Earth and most of the other planets. Martian days are called sols — short for "solar day."

Mars passed its perihelion in June 2007 and its aphelion in May 2008.

Mars is nearly twice as large as the Moon and a little over half the size of Earth, according to the Center for Mars Exploration.

Mars takes 687 earth days to go around the Sun.

Venus rotates much more slowly than Earth does, so a day on Venus is much longer than a day on Earth.

Mars is the most Earth-like other world known, yet the two planets are really a world apart.