There is a blue sunset on Mars. Why is the dawn on Mars blue and the sky red?

The photographs taken by the Mars landers are like a keyhole through which we can view the cold, harsh world of the Red Planet. This world is deadly for us, but someday people will walk on the red rocks and look at the Earth from the Martian surface. The topic of this article is the Martian sky and Martian "astronomy".

The bright white dot in this image taken by the Spirit rover's panoramic camera is the Sun.

Sunset in Ares Vallis in July 1997 at 16:10 local solar time. The colors of the image are close to true.

Sunset, "Mars Pathfinder" shot.

This image, taken by the Spirit rover's panoramic camera on May 19, 2005 (Sol 489), shows the sun setting as it approaches the rim of Gusev Crater. The colors in the image are similar to what the human eye would see, but their intensity is slightly exaggerated.

Twilight in Gusev Crater, photograph taken on the evening of April 23, 2005 (Sol 464). The colors of the photo are close to those that a person would see. The bluish color of the sky at the site of the setting Sun would be seen exactly as shown in this image, but the redness of the sky further from sunset is somewhat exaggerated.

The small star in the center of the Martian night sky is our Earth.

The image taken on April 29, 2005 (Sol 449) by the Opportunity rover shows the Martian sky about an hour after sunset, during twilight, when stars begin to appear. The dim point near the center is not a star, but our home planet.
The earth in the image appears somewhat elongated, which is explained by its movement during the shooting.

Before us is an “abyss full of stars” as seen from Mars. Due to the daily rotation of Mars, the stars stretched out into tracks.

A photo of the moons of Mars. Here, in addition to Phobos and Deimos, there are the Pleiades and Aldebaran. Image taken by Spirit on August 30, 2005 (sol 590). The right image is an enlarged view accompanied by captions.
Phobos is visible from the surface of Mars as an object approximately three times smaller than the full Moon. The orbital time of Phobos around the planet is 7 hours 39 minutes. The smaller Martian moon, Deimos, takes 30 hours and 12 minutes to orbit Mars.

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What color is the sky on Mars? Astrophysicist Santiago Perez-Hoyos about the atmosphere of Mars, the Purkin effect and the perception of the color of the Martian sky by the human eye At the moment there are many photographs of Mars, but not all of them allow us to judge the color of the sky on this planet. Many of them have too high a white balance, so our vision does not allow us to distinguish the contrasts in these photographs. Fortunately, there are some pretty interesting studies in which scientists are trying to distinguish colors in the sky of Mars and explain them by physical laws. As part of the Mars Exploration Rover program, NASA scientists delivered the Spirit, Oppotunity and Bell III rovers to the red planet. The rovers were equipped with Pancam Instrument panoramic cameras. Scientists have obtained radiometric calibrated images that can be used to determine the color of the sky. The image data was transformed into physical quantities (flux and radiance) taking into account the spectral sensitivity of the camera and filters, solar radiation reaching the surface of Mars, and other factors. Spirit and Oppotunity photographed bluish-black and black skies in layers of the atmosphere where there is no dust. However, most of the time there is a lot of dust in the atmosphere of Mars, so the sky is often a different color. The color of the sky on Mars depends on how solar radiation scatters from the direct light beam and illuminates the surface, and how the scattered rays are absorbed by molecules and particles in the atmosphere. For example, if there was no atmosphere, like on the Moon, there would be a dark sky and a yellow Sun. On Earth, the sky is blue due to Rayleigh scattering, which causes molecules with a radius smaller than the wavelength of radiation (about 1/10) to be better scattered at shorter wavelengths. In this case, the scattering cross section is inversely proportional to the fourth power of the wavelength. The atmosphere of Mars is much thinner, so molecular scattering is less effective. Martian dust may play a similar role to air molecules on Earth, which scatter short wavelengths of light and contribute to blue skies and red sunsets on Earth. On Mars, it would work the same way if the particles scattered light without any absorption. However, Martian dust is rich in blue, absorbing iron oxide, which has the opposite effect and simply deflects short wavelengths of light away from the radiation stream. The rovers took pictures of the "dark yellowish-brown" sky in the normal situation when a lot of dust remains in the atmosphere of Mars. But since dust can sometimes make the sky appear bluer (by scattering light) or redder (by absorbing light), a deeper understanding is needed. Kurt Ehlers and his colleagues conducted a study that is appreciated by anyone familiar with atmospheric optics. Ehlers and colleagues looked at the complex effect of micron-sized dust absorbing blue light and demonstrated that reddening is slightly more effective and leads to yellowish-brown skies in “dusty situations.” Additionally, longer wavelengths (red) and shorter wavelengths (blue) scatter very differently, producing interesting effects such as the blue glow that follows the Sun on its way to the Mars sky. According to this study, the sky is yellowish-brown in color, and the Sun glows blue and is especially visible during sunset. But this is more complicated than one might imagine. Since Mars is 1.5 astronomical units from the Sun, the amount of light on the surface is half that of Earth. Due to insufficient light, our eyes switch sensitivity to blue light because we switch from using color-sensitive cones to using color-blind rods. This is called the Purkin effect. So the first astronaut to land on Mars will probably describe the sky as bluer than expected.

We welcome the most curious people to the pages of our website! Today we will touch on a question that often worries inquisitive minds (especially children), but not everyone finds the opportunity to figure it out Why is the sky still blue?, because the air is actually transparent. We will try to answer it briefly.

What will Wikipedia say?

If we don’t know something, we can always find the answer in Wikipedia. So let's take a look there and see what this resource tells us.

In fact, here is a link to the necessary material.

Well said on Wikipedia! True, it’s somehow not very clear. The only thing that can be sorted out is the fact that the sun's rays reach our atmosphere, something happens to them, and we see a blue sky. No, that won’t work, let’s try to understand in more detail and in a more understandable language why the sky is blue.

In fact, the reason for this is such a concept as “ light scattering»!

Light scattering

So, the Sun emits rays that are white. White, as you know, includes all the colors of the spectrum visible to us. Evidence of this - rainbow. It occurs because sunlight hitting water droplets is refracted and breaks up into different colors. We also see blue skies for something similar.

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The fact is that there are many gas molecules in the air, which scatter sunlight. Particles of light scatter in different directions, so the blue color of the sky is visible to both earthlings and astronauts from the ISS in the form of a blue halo. But why blue, because there are at least seven colors in the spectrum, as they say: “Every hunter wants to know where the pheasant sits!”

Interesting fact! A person inhales about 20 kg of air per day. We get this volume by taking 22,000 breaths a day.

Why is the sky blue?

Each color has its own wavelength. In the following figure you can see how this indicator varies.

Violet scatters too much, and colors from green to red, on the contrary, do not scatter very intensely. So it turns out that blue and blue particles are the golden mean. Violet, despite the fact that it scatters better than blue, we do not notice because of our perception: with the same brightness, blue is perceived by our eye much better than its brother.

Here is a good video on this topic, which helped us understand this issue:

Let's summarize

1. Sunlight, interacting with air molecules, is scattered into different colors.
2. Of all the colors, blue is the color that is best prone to scattering.
3. It turns out that it actually captures airspace.

Of course, the information provided is rather exaggerated and attention should be focused on many scientific facts and concepts, but it is more or less clear, why is the sky blue.

Because the earth's atmosphere best scatters light in the blue spectrum.

On other space objects, the compositions of the atmospheres differ from the earth's or are absent altogether, therefore the sky on other planets is significantly different. On Moon, Mercury And Pluto there is no atmosphere. And nothing scatters the rays of light. Therefore, the sky on these celestial bodies is black and the stars there are very bright.

On Venus there is an atmosphere, and it does not scatter green and blue rays. Therefore, the sky on Venus is yellow, at the horizon it has a gray tint, and at the zenith it is orange.

Martian the sky is yellow-orange. This is because there is a lot of red dust in the planet's atmosphere. During sunset and sunrise, the sky on Mars is pink, and at the horizon it turns from purple to blue.

Sky color Saturn, like on Earth, blue. And just like ours, the atmosphere does not scatter the red part of sunlight.

Sky Uranus has an aquamarine color. The reason for this is the composition of the planet’s atmosphere. It mainly consists of hydrogen, helium and a small proportion of methane. The atmosphere reflects blue and green rays and absorbs red ones, which creates the beautiful color of the sky.

On Neptune the sky is blue. This is because the atmosphere is dominated by a large amount of methane gas, which strongly absorbs the red spectrum.

Gas giant - Jupiter. The planet's atmosphere consists of continuous dense clouds. And the color of the clouds changes depending on the height: the highest ones are red, then white and brown, and the lowest ones are blue.

The video of the setting sun above was taken by the Opportunity rover, which has been roaming the Martian landscape for more than 10 years.

When the Sun sets or rises on Earth, it shrinks like a melon due to atmospheric refraction. A thick layer of air adjacent to the horizon bends the light of the Sun upward, pushing the bottom of the solar disk into the upper half, which is less subject to refraction because it is higher. As soon as the Sun rises high enough and we are already looking at it through a smaller layer of the atmosphere, refraction decreases and the disk becomes round again.

You can watch videos of Martian sunsets many times, but the shape of the Sun will not change. Can you guess why? Because the air is too thin for refraction to be at all noticeable.

Twilight lingers longer on the Red Planet because dust suspended in the stratosphere reflects the sun's light for two or more hours after sunset.

So, the video itself:

And these are pictures of a Martian sunset taken by Curiosity.

During sunrise and sunset, the Martian sky at the zenith is reddish-pink, and in the immediate vicinity of the solar disk it is blue to violet.

What is the sky like on other planets?

There is no atmosphere on the Moon or on Mercury. Nothing reflects light rays. That's why the sky is black and the stars twinkle brightly on it. But from the surface of the Moon there is a stunning view of our planet.

Pluto

Almost nothing is known about Pluto's atmosphere. We know that it is quite large, but extremely sparse. In addition, the composition and size of Pluto's atmosphere changes depending on the distance from the Sun. The fact is that when moving in orbit, the distance between this dwarf planet and the Sun changes almost twice. Therefore, when Pluto is far from the Sun, its atmosphere shrinks: gases freeze and fall onto the planet in the form of ice. As Pluto gets closer to the Sun, some of the ice evaporates and Pluto's atmosphere increases. Therefore, it is quite difficult to say what color Pluto’s sky is.

Presumably this view opens from Pluto:

Venus

The atmosphere of Venus is so dense that through its thickness it is impossible to see the Sun in the sky during the day, and no one will see the stars at night. The Soviet probes of the Venus series transmitted several color images from the surface. Judging by them, the sky on Venus is dark orange or red.

Such an image was transmitted by the Venera-13 apparatus (this is a processing of old black and white photographs based on calculations).

Saturn

Saturn's skies may be the most spectacular. The composition of Saturn's atmosphere is such that the sky at the edge of the atmosphere should appear blue and turn yellow as it goes deeper. All gas planets have rings, but unlike others, Saturn has the most noticeable and largest rings. They are very clearly visible from the upper layers of the atmosphere.

Imagine a huge silver arc, consisting of many thin rings and passing through the entire sky. Small sparkles sometimes sparkle in silver rings, especially at sunrise or sunset. After sunset, this silver ribbon continues to be illuminated by the Sun.

Interestingly, the rings are only a kilometer thick, so they are almost invisible from Saturn’s equator. In a word, Saturn is worth visiting, and if a person ever gets there, he will never be disappointed in what he sees.

Uranus

The Uranian (this is how the adjective from the noun “Uranus” sounds according to the rules of the Russian language) sky should have a very beautiful bluish-green, aquamarine color. Earth is called the blue planet, although in fact from space it appears more white than blue due to the presence of white clouds in the atmosphere. The truly blue planet in the solar system is Uranus.

The planet owes its amazing color to the composition of its atmosphere. There is some methane in the upper atmosphere, which absorbs red light very well and reflects blue and green light. Therefore, the upper layers of the atmosphere will be light blue, and as you move deeper the sky will darken and turn red. Uranus also has its own system of dust rings, but they are unlikely to be visible even from the upper layers of the atmosphere, since they are very rarefied and dark.

Neptune

Neptune's atmosphere is very similar in composition to that of Uranus, but slight differences in the proportions of gases cause the color of the outer layers of the atmosphere to be bluer. We can only guess about what happens when moving deep into the atmosphere.

There are thirteen known satellites of Neptune. The largest of them, Triton, will appear slightly larger than our Moon; the next largest Proteus will be half the size. The remaining moons of Neptune are small and will be visible as ordinary stars.

Jupiter

On Jupiter, all days are cloudy. It does not have a solid surface; it is a gas giant. The gas of which it is composed simply becomes denser with depth. And at the top it forms continuous dense clouds. The colors of the clouds change with altitude: the lower clouds are blue, then brown and white, and finally red - the highest ones. Sometimes you can see the lower layers through holes in the upper ones.

The 3D image shows a simplified view of what can be seen from between the layers of clouds on Jupiter. The picture was compiled based on data obtained by cameras on the Galileo spacecraft.

Osiris

Exoplanet HD209458b is one of the first exoplanets discovered. The planet Osiris is very close to its Sun, it is a fairly large planet, according to calculations its size is about 70 percent of the size of Jupiter.

The star around which Osiris revolves is white. As it descends towards the horizon, it takes on a slightly lilac hue, as sodium in the atmosphere of Osiris absorbs light in the red and orange parts of the spectrum. Closer to the surface, the atmosphere of Osiris scatters blue light and the Star, approaching the horizon, first turns green, and then greenish-brown.

Kepler-22b

The distance from the planet Kepler-22 b to its star Kepler-22 is about 15% less than the distance from the Earth to the Sun. The luminous flux from Kepler-22 is 25% less than from the Sun. This combination gives scientists reason to believe that the surface temperature of Kepler-22 b is 22°C. It is possible that the planet is more like Neptune than Earth, that is, it is covered with an ocean.