Even the time, how long a day lasts on the Red Planet, almost coincides with the days of our planet. Mars completes a rotation on its axis in 24 hours, 39 minutes and 35 seconds.

In astronomy, sidereal and solar days are used to measure time. Sidereal days indicate the period during which heavenly body makes a revolution around its axis, being in an inertial frame of reference. Usually this is the frame of reference in relation to distant stars. A day measures the time it takes for the stars to appear in the sky in the same position as the day before.

So, the sidereal day of our planet is 23 hours, 56 minutes and 4 seconds. A solar day denotes the time during which a celestial body turns around its own axis in relation to the luminary of the solar system. In turn, they measure the time required for the Sun to take the same position in the sky as it did days before.

A sidereal day on Mars is 24 hours, 37 minutes and 22.6 seconds. Solar - 24 hours, 39 minutes and 35 seconds. Thus, a day on the Red Planet is 2.7% longer than on Earth.

Proceeding from this, the projects of modern landers for the exploration of Mars were made in order to correspond to the days of the Red Planet. Special clocks were built into them, in which the time indicators (hours, minutes and seconds) were 2.7% longer than the standard ones.

For missions to Mars in recent decades, a special "Martian time" has been developed. The work schedule of the rovers created for them was synchronized with the days of the studied object of the solar system.

The use of such clocks is important because the rovers are solar-powered, which require daylight. Also, for expeditions to Mars, they developed special clocks that included 24 hours, 39 minutes and 35 seconds, after which they moved on to the next day. But none of the projects for missions to the Red Planet decided to use them.

The zero meridian of Mars is the one that passes through the Airy-0 crater. But the planet is not divided into time zones, separated by equal intervals from the zero meridian (as on Earth). Every landing model that hit the Red Planet used the approximate local solar time as a reference point.

In 2008, a research vehicle discovered water ice at the poles of Mars (previously only carbon dioxide ice was known to exist). Later, scientists found out that precipitation in the form of snow falls from the clouds on the planet. It was later discovered that in the area South Pole the fourth planet also has carbon dioxide snow. During the year on Mars there are dust storms, sometimes covering thousands of kilometers, and interfere with the observation of a celestial body.

Mars revolves around the Sun in 686 Earth days, moving at a speed of 24,000 kilometers per second. IN modern science there is a system for designating years relative to Mars. The starting point is the day of the spring equinox of 1955, the time is considered in Martian years (Martian Year - MY).

Studying the question "How long does a day last on Mars?" shows how many discoveries even the native solar system can provide to mankind. Mars - unique planet, which resembles the Earth in some properties. Further research will reveal the mysteries of its past and the prospects for the future development of Mars by mankind.

Like all planets in the solar system, Mars rotates on its axis. Days on the red planet are replaced by nights, and a day is logically taken as the unit of measurement of Martian time. Let's try to figure out how long a day is on Mars?


Days on Earth and Mars

For people living on Earth, the system of reckoning seems completely natural. The flow of time is divided into certain intervals: minutes, days, months. This was done in accordance with the daily and annual natural cycles. The launch of interplanetary vehicles made the question of how long a day lasts on Mars urgent.

The usual 24-hour day is the period of time during which the Sun returns to the same point in the sky where it was observed yesterday. We track its movement from the surface of the planet, waiting for a reappearance at a fixed point.

The time it takes to make one revolution around an axis relative to the Sun is a solar, or synodic, day.

A day is generally considered to be exactly twenty-four hours long. In reality, their sizes are not constant due to the elliptical shape of the orbit, therefore, true and average solar days are used in accurate calculations.


Consider two axes of time - solar and stellar

The stars can also serve as a guide. But our planet, rotating, simultaneously moves in orbit and shifts slightly in a day relative to the picture of the starry sky. When the constellations return to their original position, a complete revolution relative to the Sun will not yet be completed. The planet needs to additionally rotate around its axis. This is how the difference between solar and sidereal days arises.

The time it takes for the Earth to rotate relative to the stars is called a sidereal day.

Sidereal days are shorter than solar days. To calculate their duration, we divide the equatorial length of 40,075.017 km by the equatorial rotation speed of 1674.4 km/h. Since an hour contains 60 minutes, not 100, we convert the decimal fraction into minutes and seconds and get 23 hours 56 minutes 4 seconds, or 0.997 solar days. This is the interval from the primary to the re-passage of a star through a certain, usually zero, meridian.

Planet characteristics:

  • Distance from the Sun: 227.9 million km
  • Planet Diameter: 6786 km*
  • Days on the planet: 24h 37 min 23s**
  • Year on the planet: 687 days***
  • t° on the surface: -50°C
  • Atmosphere: 96% carbon dioxide; 2.7% nitrogen; 1.6% argon; 0.13% oxygen; possible presence of water vapor (0.03%)
  • Satellites: Phobos and Deimos

* diameter at the equator of the planet
** period of rotation around its own axis (in Earth days)
*** orbital period around the Sun (in Earth days)

The planet Mars is the fourth planet of the solar system, 227.9 million kilometers away from the sun, or 1.5 times farther than the earth. The planet has a more melted orbit than the earth. The eccentric rotation of Mars around the sun is more than 40 million kilometers. 206.7 million kilometers at perihelion and 249.2 at aphelion.

Presentation: planet Mars

In orbit around the sun, Mars is accompanied by two small natural satellite Phobos and demos. Their sizes are 26 and 13 km, respectively.

The average radius of the planet is 3390 kilometers - about half of the earth's. The mass of the planet is almost 10 times less than that of the earth. And the surface area of ​​the entire Mars is only 28% of the Earth's. This is slightly more than the area of ​​all the earth's continents without oceans. Due to the small mass, the free fall acceleration is 3.7 m / s² or 38% of the earth's. That is, an astronaut weighing 80 kg on earth will weigh a little more than 30 kg on Mars.

The Martian year is almost twice as long as the Earth's and is 780 days long. But a day on the red planet, in duration, is almost the same as on earth and is 24 hours 37 minutes.

The average density of mars is also lower than that of the earth and is 3.93 kg / m³. internal structure Mars resembles the structure of the terrestrial planets. The crust of the planet averages 50 kilometers, which is much more than on earth. The 1,800-kilometer-thick mantle is composed primarily of silicon, and liquid core the planet with a diameter of 1400 kilometers is 85 percent iron.

No geological activity has been found on Mars. However, Mars has been very active in the past. On Mars, geological events took place on a scale not seen on earth. The red planet has the largest solar system Mount Olympus is 26.2 kilometers high. As well as the deepest canyon (Mariner Valley) up to 11 kilometers deep.

Cold world

Temperatures on the surface of Mars range from -155°C to +20°C at the equator at noon. Due to the very rarefied atmosphere and weak magnetic field solar radiation unhindered irradiates the surface of the planet. Therefore, the existence of even the simplest forms of life on the surface of Mars is unlikely. The density of the atmosphere at the planet's surface is 160 times lower than at the Earth's surface. The atmosphere consists of 95% carbon dioxide, 2.7% nitrogen and 1.6% argon. The share of other gases, including oxygen, is not significant.

The only phenomenon that is observed on Mars is dust storms, sometimes taking on a global Martian scope. Until recently, the origin of these phenomena was unclear. However, the latest rovers sent to the planet managed to fix dust whirlwinds that constantly appear on Mars and can reach a wide variety of sizes. Apparently, when there are too many such eddies, they develop into a dust storm.

(The surface of Mars before the start of a dust storm, the dust is only gathering into a fog in the distance, as depicted by artist Kees Veenenbos)

Dust covers almost the entire surface of Mars. The red color of the planet is due to iron oxide. In addition, on Mars it may be enough a large number of water. Dry riverbeds and glaciers have been discovered on the surface of the planet.

Moons of Mars

Mars has 2 natural satellites orbiting the planet. These are Phobos and Deimos. Interestingly, on Greek their names are translated as "fear" and "horror". And this is not surprising, because outwardly both satellites really inspire fear and horror. Their shapes are so irregular that they are more like asteroids, while the diameters are quite small - Phobos 27 km, Deimos 15 km. The satellites consist of stony rocks, the surface is in many small craters, only Phobos has a huge crater with a diameter of 10 km, almost 1/3 of the size of the satellite itself. Apparently in the distant past, some asteroid almost destroyed it. The satellites of the red planet are so reminiscent of asteroids in shape and structure that, according to one version, Mars itself once captured, subjugated and turned into its eternal servants.

The problem of clock and calendar synchronization on Earth and Mars became quite acute when the era of Mars exploration by robots began, since it was necessary to clearly know the flow of solar energy throughout both the day and the year on Mars. In this article, I propose to consider the existing ways of counting time on Mars.
Since the inclination of the axis of rotation of Mars to the orbital plane differs little from that of the earth (23°26'21" (Earth) and 25°11'24" (Mars)), it undergoes similar seasonal periods, but since the eccentricity of the orbit of Mars is much larger, the durations of the periods are quite different. Also, if the Martian day is close in duration to the Earth, then the duration of the year is different, which further enhances the desynchronization between calendars.

Days on Earth and Mars

There are two types of day - a sidereal (sidereal) day lasting 23 hours 56 minutes 4.09 s or 86164.09 seconds and an average solar day lasting 24 hours or 86400 seconds. They are not equal to each other because during the day, due to the orbital motion of the Earth, the sun shifts against the background of the stars. The mean solar day is tied to the "fictitious Sun", since the speed of the Earth's orbit, and hence the duration of the true solar day, change throughout the year.
For Mars, the corresponding periods are 24 h 37 min 22.66 s (88642.66 s) and 24 h 39 min 35.24 s (88775.24 s), respectively. As a simple calculation shows, the length of a sidereal day on Mars is 2.9% longer than on Earth, and the length of a solar day is 2.7%.
By international agreement, for devices operating on the surface of Mars, the so-called. "Martian solar day" (Sol) divided into 24 "Martian hours". Accordingly, the standard of the "Martian second" is 2.7% longer than the Earth's. This results in operators shifting their work schedule by 40 minutes each day and wearing specially designed "Martian time" watches. There were also other projects of the Martian clock. According to one of them, it was proposed to introduce metric time on Mars, setting 10 hours in a day, 100 minutes in an hour and 100 seconds in a minute, according to another, a shortened 25th hour was introduced, lasting 39 minutes 35.24 s, but these options were rejected. Sol count for spacecraft started with Sol 0 for the Viking, Mars Phoenix and MSL Curiosity missions and Sol 1 for Mars Pathfinder, MER-A Spirit and MER-B Opportunity.
The zero meridian of Mars passes through the small crater Airy-0 which has the coordinates 5°06′59.99″ S. sh. and 0°00′00″ E. e. Mars uses the planetocentric standard of longitude, which varies from 0°E to 360°E. The old planetographic standard (0° to 360° W) is used on flat charts.
Coordinated Mars Time (MTC) is analogous to Universal Time (UT). It is defined as the mean solar time at the prime meridian. The MTC designation can be misleading about similarity with the UTC standard, however MTC does not use leap seconds and the closest terrestrial counterpart to MTC is the UT1 standard. Due to the larger orbital eccentricity and different axial tilt, the difference between true solar time (WIS/LTST) and mean solar time (SST/LMST) varies much more during the year than on Earth. If on Earth the equation of time (UV = WIS - SV) ranges from “minus 14 min 22 s” to “plus 16 min 23 s”, then on Mars this difference is from “minus 50 min” to “plus 40 min”, which already a lot. In the domestic literature, the inverse difference is more often used (HC = CER - WIS). However, one should not confuse solar time with standard time, which is only formally related to solar time. There are no time zones in the usual form on Mars, and of the six rovers, five use local solar time (LMST), and the sixth (Mars Pathfinder) uses true solar time (LTST).
The MTC standard first appeared in the Mars24Sunclock program created by the Goddard Institute, replacing the AMT (Airy Mean Time) standard, which was a direct analogue of the outdated GMT standard. The AMT standard is not used in any of the missions due to its insufficient accuracy. However, now that there are clear and accurate maps of Mars, the AMT standard may once again become relevant.
For simplicity of astronomical calculations on Earth, the so-called Julian date (JD) is used, where January 1, 4713 BC is taken as the zero point. uh julian calendar or, which is the same, November 24, 4714 BC. e. Gregorian calendar. The first day was number 0. The dates change at noon. A similar date for Mars is set to Sol, coinciding with December 29, 1873 (the birth date of astronomer Carl Otto Lampland, who was the first to take astrophotography of the ever-memorable channels on Mars). Other references were 1608 (the invention of the telescope) and the vernal equinox on April 11, 1955.

A year on Earth and Mars

As was done above with the concept of a day, let's define what a year is.
Sidereal (sidereal) year - the period of orbital motion around the Sun relative to "fixed stars";
Tropical year - a period of complete change of seasons or a period during which the longitude of the Sun changes by 360 ° exactly.
These periods differ from each other by about 20 minutes (tropical is less than stellar), which is due to gyroscopic processes, in particular, precession and nutation of the planetary axis.
The duration of one revolution of Mars around the Sun is about 686.98 solar Earth days, or 668.59 sols. Since the eccentricity of the orbit of Mars (0.0934) is significantly greater than the earth's (0.0167), if we take the periods between the equinoxes and solstices as a season, then the longest season for the northern hemisphere will be spring (193 sols), and the longest short autumn(sol 142).
Just like on Earth on Mars the best option the basis of the calendar would be a tropical year, since the precession cycles on Earth and Mars are long enough to be negligible over relatively short time frames. The length of the tropical year depends on the choice of starting point. Usually, equinoxes or solstices are chosen as such a point. But usually, the vernal equinox is used for the Gregorian calendar. Since the orbit of Mars is more elongated, the differences in the length of the tropical year are slightly larger than on Earth. If for the Earth the third decimal place differs (from 365.2416 days to 365.2427 days), then for Mars the second decimal place differs significantly (from 668.5880 sols to 668.5958 sols).

Calendar

In everyday life, we use the Gregorian calendar, and not the Julian dates, for the simple reason that the cyclic calendar is much more convenient and useful in everyday life. And so the future Martian colonies will need a cyclic calendar. One of the main problems of any calendar is the intercalation of leap years. It is connected with the fact that there is not an integer number of days in a year, and if you do not take into account the correction for this, then an error very quickly accumulates between the civil calendar and the tropical year. One variant of such a calendar is the Darian calendar created by aerospace engineer and political scientist Thomas Gangale. This calendar consists of 24 months of 27-28 days and is based on a ten-year cycle with six leap years of 669 days and four ordinary ones of 668. This calendar gives an error of 1 sol per 100 years and is quite suitable for current purposes. However, at the moment, neither this calendar nor any other is used, the bill goes only to sols.

Many people first heard the word "sol" in the movie "The Martian". It tells about a man who spent a long time on Mars alone. And what is a sol on Mars and what does it calculate? Let's try to understand this issue.

The advent of salt

Since the study of the Red Planet, people have faced the problem of time calculation. At that time it was developed unique system measurement of time, called sol. So what is a sol on Mars and why is it needed? Sol is a Martian day. It is different from our earthly one.

In the automatic study of Mars, scientists are faced with the problem of ignorance about the flow of solar energy, from which the rovers are powered. And then there was an urgent need to create a Martian calendar and a special clock. They are in sync with Mars.

Since the inclination of the rotation of the Red Planet to the orbital plane is somewhat different from the Earth's, similar seasonal periods appear on the planet. However, the eccentricity of the orbit of Mars is greater, which is why the duration of the periods varies greatly. The Martian days are close to the Earth ones, but the duration of the year is different, which greatly desynchronizes the Martian and Earth calendars. Because of this, we had to develop a specific calendar and a new time calculation that works in sync with our clocks and calendars. Knowing the sun-day on Mars, the operators working with Martian machines know the time of solar energy flows.

Time on Mars

How long is a Martian day and what is a sol on Mars? Sol is called the Martian solar day. They are equal to 24 hours, 39 minutes and 35 seconds. In general, the day can be stellar and sunny. The first ones last 24 hours, 27 minutes and 22 seconds. On Earth, these figures are less: a sidereal day lasts 23 hours and 56 minutes, and a solar day lasts 24 hours. The length of a solar day changes throughout the year as the planet moves in its orbit and the Sun shifts against the background of the starry sky.

And what is the sol on Mars for scientists? By international standards for vehicles operating on the Red Planet, it is customary to use the Martian solar day, or sol, which is divided into twenty-four Martian hours. Moreover, when breaking down, it was taken into account that the duration of seconds in one minute on Mars is 2.7% longer than on Earth. Because of this feature, the work schedule of the operators is shifted every Earth day by forty minutes. Now we know what 1 sol is on Mars: it is equal to 24 hours, 39 minutes and 35 seconds on Earth.

Countdown

The knowledge of how long the sol lasts on Mars, scientists received after detailed study planets. The initial count is the zero meridian passing through a small crater. Coordinate Martian time is an analogue of universal time. It is defined as the mean solar time at the prime meridian.

According to scientists, the difference between true solar and mean solar time varies greatly throughout the year. On Earth there is a time fluctuation in the interval from minus fourteen minutes to plus sixteen minutes, on Mars these fluctuations are larger - almost an hour.

There are no time zones familiar to us on the Red Planet. Six rovers operate on this planet: five of them are in local solar time, and one is in true solar time.

A year on Mars

Like the day, there are two types of year on Earth: tropical and stellar. The latter is understood as the period of a complete change of the seasons or the period of time in which the longitude of the Sun changes by 360 degrees. sidereal year- orbital motion around the Sun relative to fixed stars. These periods diverge from each other by about twenty minutes. The same thing happens on the Red Planet.

Knowing about the concept of "sol" on Mars, how many days it is, you can calculate the Martian year. Since this planet revolves around the luminary at a slower speed than the Earth, the year here will be longer - 686 Earth days, and there will be fewer sols - 668. If we take the periods between equinoxes and solstices as seasons, then spring is considered the longest period in the northern hemisphere - it lasts one hundred ninety-three sols, and autumn - one hundred and forty-two sols.

For the basis of the Martian calendar, the tropical year is considered the most successful type of year, since the precession cycles on the planet are large. However, the length of the tropical year can be different: it all depends on the starting point. As a start, the day of the spring equinox or the day of the solstice can be chosen. But they usually use the day of the vernal equinox, since the orbit of Mars is more elongated and the indicator of the tropical year, calculated from different points counting, different.

martian calendar

There are two calendars on Earth: the Gregorian and the Julian. It is more convenient for us to use the Gregorian calculus of time: it is more convenient in everyday life. Based on this, scientists came to the conclusion that it will be more convenient for the Martian colonies of the future to live according to the cyclic (Gregorian) calendar. However, this calendar has one small problem - a leap year. In our calculation of years, the amendment occurs every four years. If it were not there, then the tropical year and our calendar would have a strong discrepancy. The same thing happens on Mars.

One of the variants of the Martian calendars was proposed by T. Gangal. He developed a calendar consisting of twenty-four months divided into 27 and 28 days. The calendar is based on a ten-year cycle with six leap years of 669 days and four of 668. According to scientists, this calendar is capable of giving an error of 1 sol per hundred years. This calculation of time is quite suitable for Mars, but it is not used. Astronomers and other scientists only count sols.

Now astronomers, cartographers and other scientists know a lot about Mars. Using all the data, they may well develop a calendar or apply the one developed by Gangale. After all, scientists have a starting point counting dates according to the AMT standard: on Earth, on the zero day, it is customary to consider the Julian date January 1, 4712 BC or from November 24, 4714 of the Gregorian calendar. The first day had a zero count, and the dates themselves changed at noon. The analogous date for Mars is Sol, which coincided with our December 29, 1873. There were other options for counting: 1608 and the day of the vernal equinox on April 11, 1955.

rovers

Mars rovers have been on the Red Planet for a long time. Moreover, every time they land on this planet, a countdown is kept, but not like ours, without dates, but sols. The operators write about the work done: “Sol 36. The rover passed from crater X to valley Y” or “Sol 128. The car hit the rock." And every scientist understands at what time it happened and where the car is now.

Conclusion

Having considered what a sol is on Mars and how many days it lasts, one can imagine how machine operators work according to such a schedule: over time, the day shifts, and at the time when we have night, it is day on the Red Planet, and vice versa.