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Mars is considered a terrestrial planet, that is, similar to Earth (as opposed to giant planets, which are about as different as planets can get from us).
Despite this, Mars is also very different from Earth. It's just over half the diameter of the Earth, with one-third of its gravity and far enough from the sun to make it cold enough – it can reach favorable temperatures for humans on the planet. equator in summer at noon, but even at night. it plumbs enough to kill a human fairly quickly.
Not that matters; the air is so thin that the temperature would not be worrying anyway. The atmospheric pressure on Mars varies enormously with the seasons (in winter, carbon dioxide literally freezes in the air, which considerably decreases the pressure), averaging about 0.6% of the Earth's level at ground level. from the sea. The air is barely there.
But this is there, even if fatally slim compared to human standards. This is still enough to have all kinds of effects on the surface, including erosion, dune construction and the creation of vast dust storms.
So there is a funny dichotomy, at least as far as the weather is concerned. There is enough air on Mars to support the weather, and in some ways it's not that different from the Earth's, but in another way, it sneakily reminds me that it's an alien planet .
For example, I recently wrote about the Mars InSight lander who takes pictures of a sunrise and sunset on Mars. Despite the strange nature of the colors – the sky is more red during the day and more blue at sunset, the opposite of what it is here – seeing the sun on the horizon evokes a sense of familiarity.
In the same press release, NASA also showed an animation taken by the InSight instrument context camera, located under the bridge of the LG instruments and equipped with a wide-angle lens ("fish-eye") in order to show as much of the Martian surface as possible around scientific instruments its robotic arm placed on the ground. The camera also sees a part of the sky and the animation shows clouds moving in the sky:
I admit being a little shocked by this animation! It sounds like it could have been a nice spring day, for example, in Arizona or New Mexico (to get red dirt everywhere). It's so … banal.
But that's do not. His March. I have to laugh at being surprised by the normal look of the video – it's pretty ironic – but I had a second shock. The animation above is raw; that is, right next to the camera, the color and brightness have not been corrected. Once this treatment is finished, the animation shows that the sky is even more blue! The images used to do this were taken towards the end of the afternoon, at sunset, so that the blue sky near the sun is jarring. On Earth, it would be white or reddish. So it's another reminder that on Mars, the familiar and the alien mingle with eagerness.
Another example of this strange juxtaposition can be seen from orbit. ESA ExoMars Trace Gas Orbiter – who just added to the mystery of methane in the Mars atmosphere – is equipped with a high-resolution camera called CaSSIS, able to detect details on Mars up to about 10 meters wide. In January, he took this magnificent shot:
(I have rotated it from the original to better adapt to the blog.)
This is not an image in natural colors; I could not find the combination of filters used, so I'm not sure of the colors (Mars Reconnaissance Orbiter's HiRISE camera does something similar sometimes, where the near infrared is mapped in red in the images, the red in green and blue / green is mapped to blue, this may be similar).
But what this shows is quite natural: all these blue runs do not come from martian dune buggies; they come from dust devils!
Dustpacks resemble tornadoes (swirls of air), although they have different origins. They are also much weaker and do not do much damage. But they are strong enough to lift the very fine, ubiquitous dust on Mars and remove it so we can see through the basalt rock below. The basalt is greyish and the dust is more red (iron oxide, ie rust), but in this picture the basalt has a bluish color and the dust is more clear. Odd, I know.
Anyway, this region of Mars, in Terra Cimmeria (in the southern mid-latitudes of the south), gets a lot of dust devils, which is pretty obvious. And that brings me back to my initial theme: dust devils are also common on Earth. I've seen dozens, small ones with leaves moving around buildings and sidewalks, huge, in Utah, full of dust and hundreds of meters high. They are incredible. Mesmerizing.
So this is another taste of what is familiar on another planet, except for their weird color. These tracks tend to fade after about a year Martian, which is another testimony of the fact that the weather does indeed exist on the red planet.
We're always learning more about Mars, and images like these help us understand. So, when you see images of space or surface, remember that, like Earth, it's a planet … but it's a different planet.
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