This is because dust storms lasting for weeks cause the atmosphere to change color.
Explanation:
Dust is a major component in the mars atmosphere . A dust storm that lasts long period will effect the visibility , atmospheric structure of the mars . There are two types of storms that are found on mars , one of them is covered large areas and last for more than six days in mars . The second one covers smaller areas and stays for short interval of time . Scientists even discovered few storms which last more than 15 to 20 martian days which are responsible for color change.
