Aram Chaos – Behind The Black

A journey into Martian chaos

April 3, 2023 5:12 pm Robert Zimmerman

Overview map of Aram Chaos

With today’s cool image, we shall begin with the overview map, and drill our way down until we get a close look at another example of truly alien Martian terrain, with only a hint of similarity to comparable geology on Earth.

The overview map to the right shows us Aram Chaos, an ancient 170-mile-wide impact crater that has gone through such complex geology that it is difficult, maybe impossible, to unravel it based on data obtained from orbit. As I wrote in a detailed December 2020 post describing the confusing geology of this crater,

The floor of Aram Chaos is a place of great puzzlement to planetary geologists. The geology there is incredibly complex, and includes chaos terrain overlain by several sedimentary layers of sulfate minerals. The chaos terrain is most obvious in the southern part of the crater’s floor. The flat areas near the eastern center are those overlaying sedimentary layers.

When we zoom into the white box we can see a good example of this complexity.
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Aram Chaos: Illustrating the puzzle of Mars

December 3, 2020 11:20 am Robert Zimmerman

Click for full image.

The geological history of Mars is incredibly complex, and we really don’t know much about it. What we do know right now is based on a limited number of tiny fragments of a much larger story, with those fragments allowing scientists to only make educated guesses on how they fit together.

Many of those guesses will certainly turn out right. Just as many will turn out wrong. At this moment in our exploration of the Red Planet we can only grasp at straws while always keeping an open mind, as later data is surely going to change any conclusions we presently have.

The photo to the right is a good illustration of this struggle. Rotated, cropped, and reduced to post here, it was taken on September 27, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what at first glance looks like a stream of white frost or ice descending down a canyon to the south.

That first impression however is entirely wrong. When I asked Chris Okubo of the U.S. Geological Survey, who requested this image from MRO, what it was, he explained,

The white material is not frost. Instead, these are sedimentary rocks comprised primarily of sulfates. The texture to me suggests these are lithified dunes.

Lithified merely means that the dunes have hardened into rock. Sulfates are a salt formed from sulfuric acid, and are on Mars often linked to some complex mineralogy. If you stood there the colors would be white and red, quite beautiful. As Okubo explained,

The sulfates are white to tan in color, but there would also be a lot of red/brown Mars dust on top of it. It would be similar to walking around some of the playas in the desert southwest.

Though these white sulfate deposits have their root in sulfuric acid, Okubo added that they “are in the form of minerals similar to gypsum and so they would be safe to touch.”

What is going on here? As is usually the case, we need to first take a wider view to get some context.
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