This is an image of a Martian storm front.
Image from: NASA
This is an image of a storm moving across the Martian land. The camera is looking down on the storm, the same way storms are presented on the news.
The storm provides evidence that there is water on Mars.
As early as 1796 scientists thought they saw "yellow", and "white" or "bluish" clouds in the Martian atmosphere. However, it wasn't until the Mariner 9 mission that clouds of water were firmly identified.
More study is needed to understand just how the clouds come and go in the Martian atmosphere. For example, even though clouds can be seen, scientists are not sure whether it actually rains on Mars.
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