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Venus is the planet with the longest day in the solar system. Description of retrograde Venus, rotation around its axis and comparison table with other planets.
To rank the length of the day on the planets of the solar system, it is important to understand what exactly we mean. The day of the planet is the time during which the body rotates its axis. We know that the Earth has 24 hours. But other solar planets are very different. At Venus the longest day among all the planets in the solar system– 243 days. This is even longer than its orbital tour - 224.65 days.
Let's compare with the indicators of other planets in order:
- Mercury: 58 days and 15 hours.
- Venus: 243 days.
- Mars: 24 hours, 39 minutes and 35 seconds.
- Jupiter: 9.9 hours.
- Saturn: 10 hours 45 minutes 45 seconds.
- Uranus: 17 hours, 14 minutes and 24 seconds.
- Neptune: 16 hours, 6 minutes and 36 seconds. But it is worth noting here that the equator and the poles rotate at different speeds.
Now let's figure out how long a day lasts on Venus. The fact is that the planet is planted closer to the star and is characterized by retrograde rotation - in the opposite direction.
Several probes have visited the surface of Venus and even managed to end up on the surface. You will be surprised, but in 1973 the possibility of a human mission was considered. The crew was to consist of three people on a Saturn V rocket and fly at a distance of 5000 km from the planet.
Spring has come. The gray and dull snow disappeared from the fields, and the sun became warmer and more gentle. Nature awakens: the first greenery begins to emerge, the buds on the trees swell and bloom, migratory birds return, and living creatures emerge from their holes and nests. Soon summer, autumn, winter will come and spring will come again. Seasons change on our planet from year to year.
But what ensures these cyclical changes in nature? The main reason for the change of seasons is the tilt of the axis of our planet relative to the ecliptic plane, i.e. the plane of rotation of the Earth around the Sun. The Earth's axis is tilted from the ecliptic plane by 23.44°. If this angle were equal to zero, the seasons would never change on the planet, the length of day and night would be the same, and the sun would rise above the horizon to the same height throughout the year.
Do seasons change on other planets in the solar system?
Mercury
If we take into account only that indicator that has a decisive influence on the formation of the seasons on Earth, the tilt of the rotation axis, then Mercury should not have the seasons we are accustomed to. However, Mercury moves in a very elongated orbit, approaching the Sun at perihelion by 46 million km and moving away by 70 million km at aphelion, which has a significant influence on the formation of Mercury's weather. Being at a short distance from the Sun, the illuminated side of Mercury heats up to an average of +300°C (maximum: +427°C) and the Mercury summer begins. In the far part of the orbit, winter sets in; even during the day at this time the temperature does not rise above 107°C, and at night it drops to -193°C.
Sunrise on Mercury occurs only once every two years (every 176 days), but it is the hottest sunrise in the entire system.
At the same time, almost no sunlight reaches the poles of Mercury due to the minimal inclination of the rotation axis to the ecliptic plane (0.01°). In these dark and cold regions, polar ice caps have been discovered, although they are only 2 meters thick.
Interestingly, a day (175.94 Earth days) on Mercury lasts twice as long as a year (87.97 Earth days).
On Venus, like on Mercury, there is also no change of seasons. Venus' rotation axis angle is an impressive 177°, in other words, this planet has an inverted orientation, and the actual inclination angle is only 3°. Orbital eccentricity, i.e. its degree of deviation from the circle is extremely small (0.01) and therefore does not make any adjustments to the weather. A hot summer reigns on the surface of the planet all year round: the average temperature exceeds +400°C.
Venus is sultry all year round, with an average temperature of about +400°C.
Mars
Mars is similar to our planet in many ways. The inclination of the axis of rotation of Mars relative to the plane of its orbit is 25.2°, which is only slightly greater than that of Earth. The eccentricity of the Red Planet's orbit is also slightly larger. As a result, the Martian climate is slightly more seasonal, meaning the differences (especially in temperature) between the different seasons are more pronounced.
Another interesting feature of the Martian seasons is that they differ significantly in different hemispheres of the planet. Thus, in the southern hemisphere there are hot summers and cold winters, while in the northern hemisphere there are no such contrasts - both summer and winter here are mild.
Jupiter
The axis of rotation of the giant planet is inclined by only 3.13° relative to the orbital plane, and the degree of deviation of the orbit itself from the circle is also minimal (0.05). In other words, the climate here is not seasonal and is constant throughout the year.
Saturn
The tilt of Saturn's rotation axis is 29°, so the change of seasons on this planet is characterized by more pronounced differences in the amount of sunlight, and therefore temperature, than on Earth. Each season - be it summer or autumn - lasts about 7 years on the giant planet. Depending on the time of year, Saturn can change its color. Eight years ago, when Cassini first approached the planet, it was winter in the northern hemisphere and this part of Saturn had a blue tint. Today the south is painted blue - winter has arrived there. According to astronomers, this phenomenon occurs due to the intensity of ultraviolet radiation - in winter it decreases, with the arrival of summer it increases.
Winter on Saturn's southern hemisphere. The blue haze that covers the south pole of the planet is a direct consequence of the drop in temperature, i.e. the arrival of winter. 10 years ago, in 2004, exactly the same blue fog shrouded the northern pole of the gas giant.
Uranus
The angle of inclination of the planet's rotation axis is 97.86° - in other words, Uranus lies on its side slightly upside down. This factor explains the rather specific change of seasons. During solstices, only one of the planet's poles faces the Sun. The change of day and night that is familiar to us is characteristic only of the equator; the remaining parts of Uranus are under the cover of the polar day or polar night for 42 Earth years.
Voyager 2 photograph of Uranus
At the pole facing the Sun, dramatic changes occur: the temperature increases significantly, the upper layers of the atmosphere begin to slowly acquire bright colors, replacing a pale blue hue, the speed of winds and the number of clouds increase.
Neptune
On Neptune, the rotation axis is tilted by 30°, so the seasons here are similar to those on Earth, but the distance of the planet from the Sun makes its own adjustments. A year on Neptune is almost 165 Earth years, therefore each season lasts, no more and no less, 41 years! Summer began in the southern hemisphere in 2005 and will last until 2046.
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How long is a day on Mars and other planets of the solar system?
November 10, 2016The Red Planet is the second name for Mars, which is located quite close to Earth. It is quite possible to observe the “neighbor” in the starry sky without a telescope.
Mars, belonging to the Terrestrial group, is the fourth planet from the Sun. For comparison: Earth occupies third position in our solar system.
The Red Planet is our “neighbor”
The name “red” is primarily associated with its hue. Due to the high content of iron oxides, the color of its surface is slightly reddish. As for the size of the planet relative to Earth, Mars is almost two times smaller. The diameter of the planet is about half that of Earth.
How long is a day on Mars?
The orbital period of Mars around the Sun is 687 Earth days. That is, a year on Mars lasts almost twice as long as on Earth. 
This is due to the fact that the distance to it is 1.62 times greater than from us to the Sun, and the orbital period naturally takes longer.
How long is a day on Mars? The length of the day on Mars is quite close to Earth's. Only this planet of our solar system has this period as close as possible to us compared to the others.
Regarding the duration, a day on Mars in hours familiar to our understanding will be 24 hours 37 minutes.
This figure slightly exceeds the Earth's day. The reason for how long a day on Mars lasts is primarily the speed of rotation of the Red Planet around its axis.
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Length of day on the planets of our solar system
The length of a day directly depends on the distance to the Sun and the speed of rotation around its own axis of each planet. There are sidereal and solar days. 
The magnitude of the difference between them depends on a combination of two factors - these are the periods of revolution around the Sun and revolution around its axis.
Let's look at the length of a day and year on other planets and compare it with how long a day lasts on Mars and Earth.
The first and closest planet to the Sun is Mercury. A sidereal day on this planet is 59 Earth days, and a solar day lasts about 176.
As for Venus, due to its rotation in the opposite direction, sidereal days have a duration of 223 Earth days, and solar days are 117 days.
The Earth has 24 hours in a solar day, the sidereal day is slightly shorter and amounts to 23 hours 56 minutes.
The length of a stellar and solar day on Mars is similar to that on Earth. And they are 24 hours 37 minutes and 24 hours and 40 minutes, respectively. That is, a day on Mars lasts 24 hours 40 minutes.
As for the giant planets, on Jupiter it is almost ten hours, on Saturn - about 10 hours 34 minutes. On Neptune it is approximately 16 hours, and on Uranus it is 17 hours and 15 minutes. The difference between solar and sidereal days on these planets is insignificant. This is due to the long period of revolution around the Sun.
As we can see, of all the planets, in terms of duration, in comparison with the Earth, Mars is the most similar.
A day on Mars, as well as on our planet, is four minutes longer than a sidereal day.
On other planets the difference is more significant; such great similarities are not observed.
A day on Mars is the same as on Earth
An expedition to Mars is planned for 2023. This time, unlike conventional probes exploring the planet, people will fly on board the spacecraft.
This rather complex mission is associated with the fact that living conditions for people are much more difficult than on their home planet, and going for a walk in open space is impossible without protective equipment.
One of the issues regarding the adaptation of new Martian inhabitants is the body’s reaction to how long a day lasts on Mars, in contrast to Earthly conditions.
Will there be a full-fledged biological adaptation? According to physiologists, such a small difference of 37 minutes will be quite easily perceived by the settlers.
Many difficulties are expected, but perhaps despite this, a day on Mars, so similar to ours, will remind astronauts of home. It’s not for nothing that the Red Planet is called Earth’s twin. Its similarity is great, but its suitability for living is minimal.
Against the backdrop of high levels of radiation, to protect the settlers, it is planned to build residential complexes specially designed to protect them from fairly harsh conditions.
There is practically no atmosphere on Mars, there is increased rarefaction. The planet's air contains mainly carbon dioxide.
As for the climate, it is quite harsh. At the equator in summer, the maximum temperature rises to +27 degrees Celsius.
At the poles it drops to -120 degrees Celsius. It is worth noting that the inclination angle on Mars is close to that on Earth and is 25 degrees.
Thanks to this, the change of seasons is similar to the usual local conditions. But still, a year on Mars is almost twice as long as on Earth and is almost 687 days.
Based on how long a day is on Mars, and from the total number of days in the Martian year, we find that the first settlers will see the Sun 668 times during the Martian year.
Astronauts of the future
In this regard, the organizers and scientists of the mission have another problem, which is technically almost solved. It is associated with the synchronization of our and Martian time. The scientific term "Sol" refers to a day on Mars, or the length of a day.
This is exactly how the new inhabitants of Mars will call their day and say that two or three sols have passed. Well, let's hope that such a grandiose mission will be successful and will open a new interplanetary era of the future.
Uranus is located at a distance of about 2.88 billion km or 19.2 astronomical units (AU) from the Sun. Since the planet follows an elliptical orbit around the Sun, the figures above represent the average distance between the planet and the Sun. At its closest point to the Sun, also known as its perihelion position, Uranus is located 2.75 billion km or 18.4 AU. e. from the Sun. At its aphelion position, or at its most distant point, Uranus moves away from the Sun by 3 billion km or 20.1 AU. e.
What is the distance between Uranus and Earth?
The distance from Uranus to Earth is constantly changing depending on the movements of both planets in their orbits. The closest distance between the two planets is 2.57 billion km, and the most distant is 3.15 billion km.
Who discovered Uranus?
Sir William Herschel, a British astronomer, made observations of Uranus on March 13, 1781. He left notes about what he saw in the garden of his home in Somerset, England, and reported the discovery on April 26, 1781, but he mistook the planet for a comet.
How did Uranus get its name?
The planet received its name directly from the name of the sky deity from Greek mythology - Uranus.
What is the density of Uranus?
The density of Uranus is 1.27 g per cm³, which is the second lowest density of any planet in the Solar System.
What is the diameter of Uranus?
The diameter of Uranus is 51,118 km, which is more than 4 times the diameter of our planet.
How many Earths can Uranus contain?
The total volume of Uranus is 6.833 × 1013 km3 and, therefore, it is capable of containing 63 of our Earths!
What is Uranus made of?
Uranus is the second least dense planet in the solar system after Saturn. This fact gives an idea of its composition. The planet is a collection of frozen methane, ammonia and water. The exact mass of Uranian ice is not known and is believed to be between 9.3 and 13.5 Earth masses. Hydrogen and helium account for the rest of the planet's mass. Uranium consists of three main layers: an inner rocky core, a middle mantle of ice, and an outer gaseous layer that includes hydrogen and helium.
How many rings does Uranus have?
Uranus is surrounded by 13 known rings, ranging in radius from about 38,000 km to about 98,000 km. They are formed, as a rule, from relatively large bodies with a diameter of 0.2-20 m.
Atmosphere of Uranus
Uranus has a unique atmosphere consisting of three layers: the troposphere, stratosphere and thermosphere. The planet's atmosphere is considered the coldest in the solar system and can cool to a temperature of -224º C. The lower layers of the atmosphere are rich in volatile substances such as methane, water and ammonia. The upper atmosphere mainly contains hydrogen and helium.
How many moons does Uranus have?
Uranus has 27 natural satellites. However, the moons of Uranus are the smallest among the other moons. Uranus' largest moon, Titania, has a radius of 788.9 km, making it the eighth largest moon in the Solar System. Satellites are typically made of rock and ice in a ratio of about 1:1.
What is the temperature of Uranus?
Uranus is one of the. Temperatures near the planet's cloud tops can drop to -216º C. The lowest temperature recorded at the tropopause of Uranus is -224º C.
Can Uranus support life?
It is quite difficult to answer the question of whether Uranus will be able to support life, since the planet has conditions that both promote and also hinder the survival of living organisms. Uranus has an abundance of methane, which is a key biosignature. There is a possibility that a liquid ocean consisting of water is present near the planet's core. Although, the bad news is that in the heart of the planet there is enormous pressure that no life form known to us can withstand. In addition, Uranus has the coldest atmosphere in the solar system. Thus, no terrestrial life can survive in such extreme conditions, but specially adapted extraterrestrial life could be used.
Here on Earth, we tend to take time for granted, never considering that the increments in which we measure it are quite relative.
For example, the way we measure our days and years is actually a result of our planet's distance from the Sun, the time it takes to revolve around it, and to rotate on its own axis. The same is true for other planets in our solar system. While we Earthlings calculate the day in 24 hours from dawn to dusk, the length of one day on another planet differs significantly. In some cases, it is very short, while in others, it can last more than a year.
Day on Mercury:
Mercury is the closest planet to our Sun, ranging from 46,001,200 km at perihelion (closest distance to the Sun) to 69,816,900 km at aphelion (farthest). Mercury takes 58.646 Earth days to rotate around its axis, meaning that a day on Mercury takes approximately 58 Earth days from dawn to dusk.
However, it takes Mercury only 87,969 Earth days to circle the Sun once (aka its orbital period). This means that a year on Mercury is equivalent to approximately 88 Earth days, which in turn means that one year on Mercury lasts 1.5 Mercury days. Moreover, Mercury's northern polar regions are constantly in shadow.
This is due to its axial tilt of 0.034° (compared to Earth's 23.4°), meaning Mercury does not experience extreme seasonal changes, with days and nights lasting for months, depending on the season. It is always dark at the poles of Mercury.
A day on Venus:
Also known as "Earth's twin", Venus is the second closest planet to our Sun - ranging from 107,477,000 km at perihelion to 108,939,000 km at aphelion. Unfortunately, Venus is also the slowest planet, a fact that is obvious when you look at its poles. Whereas the planets in the solar system experienced flattening at the poles due to their rotational speed, Venus did not survive it.
Venus rotates at a speed of only 6.5 km/h (compared to Earth's rational speed of 1670 km/h), which results in a sidereal rotation period of 243.025 days. Technically, this is minus 243.025 days, since Venus's rotation is retrograde (i.e., spinning in the opposite direction of its orbital path around the Sun).
Nevertheless, Venus still rotates around its axis in 243 Earth days, that is, many days pass between its sunrise and sunset. This may seem strange until you know that one Venusian year lasts 224,071 Earth days. Yes, Venus takes 224 days to complete its orbital period, but more than 243 days to go from dawn to dusk.
Thus, one Venus day is slightly more than a Venusian year! It's good that Venus has other similarities with Earth, but it's clearly not a daily cycle!
Day on Earth:
When we think of a day on Earth, we tend to think of it as simply 24 hours. In truth, the sidereal rotation period of the Earth is 23 hours 56 minutes and 4.1 seconds. So one day on Earth is equivalent to 0.997 Earth days. It's strange, but then again, people prefer simplicity when it comes to time management, so we round up.
At the same time, there are differences in the length of one day on the planet depending on the season. Due to the tilt of the Earth's axis, the amount of sunlight received in some hemispheres will vary. The most striking cases occur at the poles, where day and night can last for several days and even months, depending on the season.
At the North and South Poles during winter, one night can last up to six months, known as the "polar night". In summer, the so-called “polar day” will begin at the poles, where the sun does not set for 24 hours. It's actually not as simple as I would like to imagine.
A day on Mars:
In many ways, Mars can also be called “Earth’s twin.” Add seasonal variations and water (albeit frozen) to the polar ice cap, and a day on Mars is pretty close to a day on Earth. Mars makes one revolution around its axis in 24 hours. 
37 minutes and 22 seconds. This means that one day on Mars is equivalent to 1.025957 Earth days.
Seasonal cycles on Mars are similar to ours on Earth, more than on any other planet, due to its 25.19° axial tilt. As a result, Martian days experience similar changes with the Sun, which rises early and sets late in the summer and vice versa in the winter.
However, seasonal changes last twice as long on Mars because the Red Planet is at a greater distance from the Sun. This results in a Martian year lasting twice as long as an Earth year—686.971 Earth days or 668.5991 Martian days, or Solas.
Day on Jupiter:
Given the fact that it is the largest planet in the solar system, one would expect the day on Jupiter to be long. But, as it turns out, a day on Jupiter officially lasts only 9 hours, 55 minutes and 30 seconds, which is less than a third of the length of an Earth day. This is due to the fact that the gas giant has a very high rotation speed of approximately 45,300 km/h. This high rotation rate is also one of the reasons why the planet has such strong storms.
Note the use of the word formal. Since Jupiter is not a solid body, its upper atmosphere moves at a different speed than at its equator. Basically, the rotation of Jupiter's polar atmosphere is 5 minutes faster than that of the equatorial atmosphere. Because of this, astronomers use three reference frames.
System I is used in latitudes from 10°N to 10°S, where its rotation period is 9 hours 50 minutes and 30 seconds. System II is applied at all latitudes north and south of them, where the rotation period is 9 hours 55 minutes and 40.6 seconds. System III corresponds to the rotation of the planet's magnetosphere, and this period is used by the IAU and IAG to determine the official rotation of Jupiter (i.e. 9 hours 44 minutes and 30 seconds)
So, if you could theoretically stand on the clouds of a gas giant, you would see the sun rise less than once every 10 hours at any latitude of Jupiter. And in one year on Jupiter, the Sun rises approximately 10,476 times.
Day on Saturn:
The situation of Saturn is very similar to Jupiter. Despite its large size, the planet has an estimated rotation speed of 35,500 km/h. One sidereal rotation of Saturn takes approximately 10 hours 33 minutes, making one day on Saturn less than half an Earth day.
Saturn's orbital period is equivalent to 10,759.22 Earth days (or 29.45 Earth years), with a year lasting approximately 24,491 Saturn days. However, like Jupiter, Saturn's atmosphere rotates at different speeds depending on latitude, requiring astronomers to use three different reference frames.
System I covers the equatorial zones of the South Equatorial Pole and the North Equatorial Belt, and has a period of 10 hours 14 minutes. System II covers all other latitudes of Saturn except the north and south poles, with a rotation period of 10 hours 38 minutes and 25.4 seconds. System III uses radio emissions to measure Saturn's internal rotation rate, which resulted in a rotation period of 10 hours 39 minutes 22.4 seconds.
Using these different systems, scientists have obtained various data from Saturn over the years. For example, data obtained during the 1980s by the Voyager 1 and 2 missions indicated that a day on Saturn is 10 hours, 45 minutes and 45 seconds (±36 seconds).
In 2007, this was revised by researchers in UCLA's Department of Earth, Planetary and Space Sciences, resulting in the current estimate of 10 hours and 33 minutes. Much like Jupiter, the problem with accurate measurements stems from the fact that different parts rotate at different speeds.
Day on Uranus:
As we approached Uranus, the question of how long a day lasts became more complex. On the one hand, the planet has a sidereal rotation period of 17 hours 14 minutes and 24 seconds, which is equivalent to 0.71833 Earth days. Thus, we can say that a day on Uranus lasts almost as long as a day on Earth. This would be true if it were not for the extreme tilt of the axis of this gas-ice giant.
With an axial tilt of 97.77°, Uranus essentially revolves around the Sun on its side. This means that its north or south points directly toward the Sun at different times in its orbital period. When it is summer at one pole, the sun will shine continuously there for 42 years. When the same pole is turned away from the Sun (that is, it is winter on Uranus), there will be darkness there for 42 years.
Therefore, we can say that one day on Uranus, from sunrise to sunset, lasts as long as 84 years! In other words, one day on Uranus lasts as long as one year.
Also, as with other gas/ice giants, Uranus rotates faster at certain latitudes. Therefore, while the planet's rotation at the equator, approximately 60° south latitude, is 17 hours and 14.5 minutes, the visible features of the atmosphere move much faster, completing a complete rotation in just 14 hours.
Day on Neptune:
Finally, we have Neptune. Here, too, measuring one day is somewhat more complicated. For example, Neptune's sidereal rotation period is approximately 16 hours, 6 minutes and 36 seconds (equivalent to 0.6713 Earth days). But due to its gas/ice origin, the planet's poles replace each other faster than the equator.
Considering that the planet's magnetic field rotates at a rate of 16.1 hours, the equatorial zone rotates approximately 18 hours. Meanwhile, the polar regions rotate within 12 hours. This differential rotation is brighter than any other planet in the Solar System, resulting in strong latitudinal wind shear.
In addition, the planet's axial tilt of 28.32° leads to seasonal variations similar to those on Earth and Mars. Neptune's long orbital period means that a season lasts for 40 Earth years. But since its axial tilt is comparable to Earth's, the change in the length of its day during its long year is not so extreme.
As you can see from this summary of the various planets in our solar system, the length of the day depends entirely on our frame of reference. In addition, the seasonal cycle varies depending on the planet in question and where on the planet the measurements are taken.