How Long is a Day On Other Planets?

Our solar system is made up of eight planets that orbit around the sun. There are also five planets identified as dwarf planets and other smaller solar objects which together also orbit around the sun. There are four planets categorized as inner planets: Mercury, Venus, Earth, and Mars, and they are among the smallest. On the other side, there are terrestrial planets which are made up mainly of metals and solid rocks, and they are the four outer planets also known as giant planets which include Jupiter, Saturn, Uranus, and Neptune. The planets Saturn and Jupiter are the largest, and they are gas planets which are made up of helium and hydrogen, while Neptune and Uranus are the outermost planets, and they are made up of volatiles such as methane ammonia and water.

Mercury 

58 Earth days

Mercury is about 35.98 million miles from the sun. It takes Mercury approximately 58.64 Earth days (1,408 hours) to rotate on its axis, also known as the sidereal time. It takes about 175.97 Earth days from one sunrise to another, and this is due to the planet’s proximity to the sun and its high speed of orbiting around the sun. It will take approximately 176 days for the planet to experience one sunrise to another sunrise. The orbital time or the time the planet takes to go around the sun is 89.969 Earth days, implying that Mercury has a year which is equivalent to 88 days on Earth. A single year on the planet Mercury lasts about half as long as its day.

Venus

243 Earth days

Venus is the second planet after Mercury that is closer to the sun and lies in a distance of about 67.24 million miles away from the sun. The planet is among the slowest in our solar system because all other planets have experienced flattening on both poles as a result of speeds of their spinning a characteristic which is lacking on Venus. The rotational speed of Venus is 4.0 mph in comparison to the rotational velocity of the Earth, which is 1,040 mph. The planet is a retrograde rotation planet, meaning that it is rotating in the opposite direction of its path it takes around the sun. Venus takes 243.025 Earth days (5,832 hours) to turn once on its axis. Just like Mercury, the slow rotation and the orbital speed of Venus imply that one solar day or the time taken for the sun to appear in the same location in the sky is 117 days. Therefore one year in Venus translate to about 224.70 Earth days and during this time the planet experiences only two sunrises and two sunsets. One year on the planet takes as long as 1.92 days of the planet Venus.

Earth

24 Earth hours 

Earth rotates once on its axis in exactly 23 hrs 56 mins and 4.1 secs. On the other hand, it takes an average of 24 hours for one solar day on Earth, and it means that this is the duration it takes the sun to show up again in the same position in the skies. On Earth, a cycle of a one day and night is 24 hrs. Our planet Earth takes 365.256 days to go around the sun.

Mars

24 Earth hours, 37 minutes 

One day on the planet Mars is nearly equivalent to a single day on Earth which takes 24 hrs, 37mins and 22 secs to spin once on its axis, and this implies that a single day on Mars is the same as 1.025957 Earth days (25 hours). Mars has some similarities with the planet Earth having a tilt of 25.19 degrees compared to Earth, which is tilted at 23.4 degrees. Variation in seasons on Mars takes almost twice as long compared to the seasons on Earth, due to the distance of the planet from the sun. Consequently, one year on Mars lasts almost twice as long as on Earth, which is 680 6.71 Earth days and translates to 2,668.599 Martian days.

Jupiter

9 Earth hours, 55 minutes 

Jupiter is the largest planet and the Jovian day (a day on Jupiter) is only 9 hrs 55 mins and 30 secs, a length which is about 1/3 the length of the day on Earth. The reason why the giant planet has a shorter day is because of its rotational velocity with is 28,148.1 15 mph at the equator. Since the planet is not solid, the rotational speed at the equator is higher compared to the rotational speed at the poles. On Jupiter, the sun would be seen on the same point on the sky in about 10 hours. In one Jovian year, the sun will rise and set for approximately 10,476 times.

Saturn

20 Earth hours, 33 minutes 

The planet Saturn experiences almost the same situation as Jupiter, and the rotational speed of the planet is 22,058.67 7 miles per hour. This implies that the planet takes an average of 10 hrs and 33 mins to complete one sidereal rotation, and therefore a day on the planet Saturn is less than half a day on planet Earth. Saturn also takes the comparable of 29.4 57 Earth years or 10,759.2 Earth days to go or orbit around the sun and therefore one Cronian year (a year on Saturn) is equivalent 24,491 Saturnian days.

Uranus

17 Earth hours, 14 minutes 

The sidereal rotation of the planet Uranus takes 17 hrs, 14 mins and 24 secs, which is about 0.71833 days on Earth. The planet has a tilt of 97.7 7 degrees making one of the poles point almost directly to the sun during its orbital journey around the sun. Therefore, during summer on the planet, one side will experience continuous sunlight for 42 years while one side which is facing away from the sun will experience perpetual darkness for 42 years as well. Therefore, one single day in Uranus, which is the duration from one sunrise the next sunrise would typically last for 84 years. In other words, one Uranian day is the same as one Uranian year, which is equivalent to 84.025 Earth years.

Neptune

16 Earth hours, six minutes 

Neptune has a sidereal rotation of approximately 16 hrs, 6 mins, and 36 secs, which is equivalent to about 0.6713 days on Earth. Neptune is a gas planet and has different rotational speeds on different latitudes. The rotational speed around the equator zone takes approximately 18 hrs, while at the extreme poles it takes about 12 hrs, and this is the highest differential rotational speed in all the planets in the solar system.