In the Martian atmosphere, there are three types of clouds, which are classified:
Type I – “Blue” clouds
So called because they are visible with the aid of short wavelength filters (violet or indigo).
Type II – Yellow clouds
So named because they are well observed through long-wavelength filters (yellow, orange and red).
When observing Mars with one of these filters, the contrast between the light and dark regions is highlighted; and the yellow clouds become white through these filters, which makes it easy to identify.
Type III – White clouds
So called because they are that color and also seen in full light (without the use of filters).
In this photo, in addition to the most common blue limbo clouds, we can see some scattered white ones, mainly over the Volcanoes east of Mount Olympus, which was very visible.
