What is the climate change on Mars?

The atmosphere of Mars is very thin, with an average surface pressure of only 7.5 millibars (about 0.75% of the Earth's). The composition is 95% carbon dioxide, 3% nitrogen, 1.6% hydrogen, a little oxygen, water vapor, carbon monoxide, neon, krypton, xenon, etc. And it's covered with dust. The surface temperature can reach 28℃ during the day and as low as-132℃ at night, with an average of -57℃. Although the amount of carbon dioxide is several times that of the earth, due to the lack of water vapor, the greenhouse effect is only 10℃, which is lower than the earth's 33℃.

atmospheric structure

According to the temperature change, the Martian atmosphere can be divided into four layers: lower atmosphere, middle atmosphere, upper atmosphere (hot air layer) and escape layer.

Mars climate

Because the rotation axis of Mars is obviously tilted, there are also obvious seasonal changes, but a season is about twice that of the earth. Another difference with the earth is that the orbital eccentricity of Mars is greater than that of the earth, that is, the perihelion and apohelion of Mars are very different. When it is located at perihelion, the temperature rise in summer in the southern hemisphere is stronger than that caused by apohelion in the northern hemisphere, and the winter in the northern hemisphere is also colder than that in the southern hemisphere.

atmospheric circulation

The atmospheric circulation of Mars is mainly single-cell circulation, which rises from the equatorial relative hot air, drifts to the polar subsidence, and then returns to the equator along the ground. In addition, in the summer hemisphere of Mars, the carbon dioxide in the polar cap sublimates into the atmosphere, raising the air pressure; In the winter hemisphere, due to the condensation of carbon dioxide, the air pressure drops. Because the amount of carbon dioxide entering and leaving the atmosphere is as high as 25%, resulting in the pressure difference between north and south, air tends to flow from the high-pressure summer hemisphere to the low-pressure winter hemisphere, forming another circulation that changes direction with the seasons. Therefore, the weather system on Mars is often global, such as sandstorms.

A sandstorm/demon

Because of the low air pressure on Mars, when the sun shines on the earth's surface, the atmosphere can quickly increase kinetic energy, with high wind speed and low gravity, and dust is easily caught in the air. The temperature in the southern hemisphere rises rapidly in spring and summer, which is easy to form strong winds. The rolling crazy sand is further heated, and the wind speed is faster, eventually forming a sandstorm. From space, you can see a brown dust cloud spinning and moving. Some of these regional sandstorms even developed into global sandstorms, which enveloped the whole earth in orange fog. When Mariner 9 arrived on Mars, Mars was covered by global sandstorms and could not be observed.

dust whirl

Dry desert areas often occur on the earth, as well as on Mars. A dust storm is like a mini tornado. When the surface is heated, the air above it rises and rotates, carrying sand and gravel, walking on the surface, leaving a dark track because it takes away the shallow sand on the upper layer.

Clouds on Mars and Antarctic crowns

Clouds on Mars and Antarctic crowns

cloud

Clouds on Mars are not as thick as those on Earth. Due to the cold, dryness and low pressure, the clouds on Mars are usually few and thin. Some are made of water ice and some are made of dry ice. If mixed with sand and dust, they will turn from white to yellow Huang Yun. Other common clouds, such as mountain clouds in the mountains of Tarsis and Elusim, equatorial clouds common in Hubble Space Telescope, and Yun Lan on the edge of Mars.

The discovery of methane

In 2003, ground-based telescopes discovered methane in the atmosphere of Mars. In March 2004, the Mars Odyssey confirmed this discovery. The existence of methane is very interesting, because it is an unstable gas, which can be easily decomposed into free carbon and hydrogen by strong ultraviolet rays, so there must be some unknown source, volcanism, comet or asteroid impact, methane archaea on Mars now (or in recent centuries).