![]() ![]() and then they would go back to being dark once again.įor a long time, we didn’t know why, until we started noticing that the dark areas that change all had a few things in common, particularly when compared to the dark areas that didn’t change. ![]() they would get covered in dust that we suspect was from the brighter areas,.In particular, we’d notice that there were darker areas and brighter areas, and that the dark areas would evolve in a particular pattern: Ever since we began examining the Martian surface in detail - first from orbiting missions and, later, landers and rovers - we noticed that surface features would change over time. When we look at the Martian surface itself, however, the story gets far more interesting. NASA / JPL-Caltech / Cornell / Arizona State Univ. Top image is in “true color,” as human eyes would see Mars, while the bottom is in false-color enhanced for color contrast. The same panoramic composite image, taken by Opportunity, shown with two different color. That’s the right size and composition so that the rapid Martian winds, which typically blow at speeds close to ~100 km/hr, continuously sweep large amounts of dust up into the atmosphere, where it remains fairly well-mixed, even when there are no dust storms. The particles that make up this hematite are small: between about 3 and 45 microns in diameter. When we look at the dust in detail, particularly with the OMEGA instrument on ESA’s Mars Express mission, we find that the most common type of dust comes from nanocrystalline red hematite, which has the chemical formula α-Fe 2O 3. and are rich in iron: i.e., containing large amounts of ferric oxides.Just from looking at its spectral properties - or “how it affects the light” - we can see that the dust is very similar to the regions on Mars that: If you look at the suspended atmospheric dust in detail on Mars, and ask, “what is it like,” the answer is incredibly informative. This is consistent with small hematite dust particles suspended in the Martian atmosphere, with the opacity increasing with increased dust density. ![]() severely suppressed in shorter (bluer) wavelengths. Compared to the irradiance received at Earth's surface, the light received on Mars's surface is. ![]()
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