Spending the Winter Solstice on Mars? It Did!

The northern hemisphere of Mars, where the Zhurong rover is located, ushered in the winter solstice on July 21, and the northern hemisphere of Mars also entered the coldest season of the year. Why does Mars also have a winter solstice? What are the four seasons on Mars like? Astronomy experts from the Chinese Academy of Sciences reveal the secrets for you.

Image courtesy of China National Space Administration

Like Earth, Mars rotates on its own body while orbiting the sun, so Mars also has day and night and four seasons. When the sun's direct point on Mars is at the southernmost point, it is the winter solstice. This year, it ushered in the winter solstice on July 21.

Wang Kechao, director of science popularization at Purple Mountain Observatory, Chinese Academy of Sciences: This is because the inclination of Mars' rotation axis is 25.19 degrees, which is very similar to that of the Earth. During one orbital cycle, the sun's direct point also moves back and forth between 25.19 degrees north and south latitude. When the sun's direct point is at the southernmost end, that is, 25.19 degrees south latitude, it is the winter solstice on Mars.

Image courtesy of China National Space Administration

Unlike Earth, Mars' orbital period is about 687 Earth days, that is, one Martian year is equivalent to about 1.9 Earth years, and its last winter solstice was September 2, 2020. At the same time, Mars' orbit around the sun is much flatter than Earth's orbit, so the length of the four seasons on Mars is relatively more uneven.

Wang Kechao, director of science popularization at Purple Mountain Observatory of the Chinese Academy of Sciences: Each of its seasons is longer than those on Earth. The eccentricity of Mars' orbit is relatively large, which results in Mars' speed being fast and the time being short when passing through the perihelion, and the time being longer when passing through the aphelion. The winter on Mars is located near the perihelion, so for the northern hemisphere of Mars, its spring and summer are about one-third longer than its autumn and winter.

Image courtesy of China National Space Administration

It is understood that the distance between Mars and the Sun is about 1.5 times the distance between the Sun and the Earth. Mars receives less solar radiation energy, only 43% of that of the Earth. Therefore, Mars is colder and sandstorms are more likely to occur in winter.

Wang Kechao, director of science popularization at the Purple Mountain Observatory of the Chinese Academy of Sciences: The temperature on Mars will be colder in each season. For example, in the current winter, the temperature in the northern hemisphere of Mars can drop to more than 100 degrees Celsius below zero, which is colder than any place on Earth. In addition, winter on Mars is a season of frequent sandstorms. However, since the atmospheric pressure on Mars is less than 1% of that on Earth, its storms can only blow up floating dust, and are not as violent as sandstorms on Earth.

Source: CCTV News

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