Why is the sunset on Mars blue and the earth red?

Sunset is a miracle of the universe, which touches everyone's thinking soul.

From painting to poetry to exquisite photos, the colors of red, orange and pink that cover the sky at dusk awaken all of us to introspection and artistic sparks.

However, if you take Musk's rocket to Mars and decide to watch the sunset on this red planet, you will be surprised!

Unlike the earth, the sunset on Mars is not decorated with rich red.

This amazing sunset photo of Mars was taken by NASA's Spirit rover in 2005.

The picture shows a blue and white sun surrounded by a blue halo, which is quite different from the appearance of a sunset on the earth.

There is a fascinating relationship between the earth and the Martian sky.

The sky of our pale blue planet is dominated by blue, which turns orange-red at dawn and dusk.

Coincidentally, the red planet Mars also has a clear orange-brown sky, which gently turns into a blue palette at sunset.

The same sun shines on two planets. Why are their colors so different?

Mars is much farther from the sun than the earth.

Therefore, from Mars, the sun looks smaller and darker.

According to the data collected by various Mars probes, from the surface of the planet, the sun has a blue-white shadow.

In addition, at sunset, the sun seems to be surrounded by a blue halo, which gradually disappears and blends with the red-gray Martian sky.

But what caused this? The secret lies in the atmosphere of Mars.

The sun emits a series of electromagnetic radiation, from high-frequency gamma rays to low-frequency radio waves.

Part of this radiation is called visible spectrum, which can be detected by our eyes.

This visible spectrum, which we usually define as "white light", is further composed of seven different wavelengths, and we all know the famous abbreviation ROYGBIV.

In short, the same electromagnetic radiation reaches different planets with different intensities.

Why is the sky and the sun on every planet completely different in color?

This is because, besides sunlight itself, the color we see depends on something else: the medium through which it passes.

Light has different interactions with different particles.

When it meets particles, light will be absorbed, reflected or scattered.

The extent to which this happens depends on the nature of the particles with which it interacts.

Some particles tend to scatter longer red wavelengths, while others tend to scatter shorter blue wavelengths.

So in the process of light propagation, some wavelengths will be removed, and the color of the result we see will change accordingly.

For example, in outer space where no particles scatter or absorb light, the sun looks white.

Why does the sunset on the earth look red?

This is because of something called Rayleigh scattering, which occurs when the particle size is very small compared with the wavelength of light.

Tiny nitrogen and oxygen molecules in the earth's atmosphere scatter blue wavelengths, so when light reaches our eyes, only red is left.

Now, in order to understand why the sunset on Mars is blue, we first need to check the composition of the Martian atmosphere.

The density of the Martian atmosphere is almost 80 times that of the Earth.

The thin atmosphere of Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon and less than 1% oxygen.

However, there are other things that dominate the Martian atmosphere-dust particles.

The surface of Mars is covered with dust particles of zeolite, hematite, olivine and magnetite. These particles are the main factors that cause the blue sunset on Mars.

As mentioned earlier, the scattering of light depends on the size of particles.

Smaller particles in the earth's atmosphere are beneficial to Rayleigh scattering, but the situation on Mars is different.

The size of dust particles suspended in the atmosphere is between 400 and 700 nanometers, which is almost equal to the wavelength of visible light;

Therefore, these particles cannot undergo Rayleigh scattering.

Instead, they follow a different optical phenomenon, triple scattering.

Michaelis scattering is the main type of scattering in larger particles.

Unlike Rayleigh scattering, this phenomenon is independent of wavelength.

On the contrary, this scattering is more dependent on the direction of light.

Here, the scattering of light occurs more in the forward direction than in the lateral or backward direction.

Generally speaking, Michaelis scattering is called uniformly scattering light of all wavelengths.

However, according to the size of particles and the direction of incident light, their main scattering wavelengths will be different.

For example, dust particles in the atmosphere of Mars scatter more red light than blue light.

Coupled with the existence of a large number of red iron oxide, this is why the Martian sky is red.

When we analyze the sunset on Mars, we immediately notice two characteristics.

One is the blue disk of the sun, and the other is the fading blue halo around the sun.

Why do these appear?

Seen from Mars, the sun looks blue because the Martian atmosphere filters out more red wavelengths.

Dust on Mars is very suitable for scattering red light, so these particles scatter red wavelengths more times than blue wavelengths.

Because sunlight travels the longest distance at sunrise and sunset, when it covers its long path, the red light is "extinct", leaving only a short blue wavelength.

This is called wavelength selective extinction, which is why the sun looks blue.

In short, the atmosphere is considered as a filter for sunlight.

The earth's atmosphere is good at filtering blue light and letting red light in, while the Martian atmosphere is better at filtering red light and letting blue light in.

The fascinating blue light around the sun cannot be simply explained by wavelength selective extinction.

Here, the scattering mode is also important.

As mentioned earlier, Michaelis scattering strongly depends on the direction of light, and it is more dominant in the forward direction.

Therefore, when passing through the Martian atmosphere, most of the light will be scattered forward at a small angle.

Therefore, what we see is not the blue hue on the horizon, but more small and concentrated blue rings around the sun.

In addition, different colors have different scattering modes.

In the forward direction, the intensity of blue light is almost six times that of red light.

This is why we see brighter blue shadows near the sun.

The maximum intensity of blue light is observed at the scattering angle of 10 degree.

Then with the increase of scattering angle, the advantage of blue wavelength begins to decline.

When the scattering angle exceeds 28 o, the intensity of red wavelength becomes more significant, so the blue light slowly disappears in the red-gray sky of Mars.

In short, the blue color of the sun is due to wavelength selective extinction, while the blue halo is the result of angular scattering of sunlight caused by Michaelis scattering.

Now, are you depressed because you can only watch the blue sunset on Mars?

After all, Musk's rocket can only carry four passengers at a time, and the price of each seat is as high as hundreds of millions of dollars.

Don't worry, because occasionally you can see the blue sunset on the earth.

1883 After the eruption of Krakato volcano, the local people reported that the sun and the moon in this area have been blue for more than a month.

At about the same time, a Hawaiian bishop named Reverend Sereno reported that he had witnessed a blue halo around the sun, surrounded by a brown halo.

This phenomenon is caused by large volcanic dust particles ejected into the atmosphere after volcanic eruption, and it is named "Bishop's Ring" after the priest who first described it.

In addition to volcanic eruptions, blue sunsets are also reported from time to time in the Arabian desert where sandstorms frequently occur.

Sometimes, forest fires can also lead to red skies and blue sunsets.

Apart from all the other factors mentioned above, the color of the sunset on Mars depends largely on something else-our eyes!

The true color of the sunset on Mars can only be described after human perception.

Until then, we can only watch it through the images sent back by the Mars probe, or wait to see the blue sunset on the earth.

Besides, you can also choose to be an astronaut and go to Mars to watch the blue sunset.

Or, set a small goal, earn hundreds of millions, and then you can buy Musk's rocket ticket.

How's it going? Do you feel that life is suddenly full of hope?

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