Arabia Terra – Behind The Black

Layers upon layers on Mars

February 28, 2023 3:47 pm Robert Zimmerman

Click for original image.

Today’s cool image once again illustrates that the geology of Mars will almost certainly center on a study of layers, as increasingly the orbital and rover images are telling us that the red planet is covered with innumerable layers, one after another, each created by another cycle, some seasonal, some global, and some related to climate and the planet’s fluctuating rotation tilt as well as its orbit around the Sun. And some might also be random volcanic events, unrelated to the cycles.

The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on October 10, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled by the science team “Layering in western Arabia Terra”, this section only shows a small amount of the layering visible in the full image. From east to west the ground rises in a series of terraces, each representing a different layer of distinct geology.
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Terraced serrated layered mesas on Mars

February 10, 2023 2:34 pm Robert Zimmerman

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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on November 19, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a collection of terraced mesas covered with dust of a variety of colors.

The bluish colors suggest exposed bedrock, while the different shades of tan suggest areas covered by dust and volcanic ash. That the tan areas are likely dust is strengthened in that it is found between and on these rough mesas, where dunes are also seen. The dust gets blown in but gets trapped there.

The tan colors however could also indicate different types of bedrock, especially because different terraces seem to be of different shades. We will need more data to determine which, or whether this is a combination of all these geological processes.
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Midnight repost: It’s the hate, not the violence

July 16, 2020 11:59 pm Robert Zimmerman

The tenth anniversary retrospective of Behind the Black continues: Though tonight’s essay was written in June 2017 it still applies today. The mindless hate that moves the left has now escalated beyond Trump and the Republican Party to encompass all of American history.

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It’s the hate, not the violence

The last few days have probably been the ugliest I have ever seen in American culture. Not only was an attempt made to commit mass murder against a group of Republican elected officials, the response from too many mainstream Democrats has generally been tone deaf and even supportive of the violence. Worse, the violence appears to be on-going, with no sign of relief.

My list is hardly complete. The stories above are only a small sampling of the ugly stuff I have read since the shooting on June 14. The best I have seen from some Democrats is a hint that maybe they have let their rhetoric get out of hand, but even here they often backtrack to blame Republicans and only Republicans for the shooting.
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Monument Valley on Mars

July 14, 2020 12:58 pm Robert Zimmerman

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Today’s cool image is located near the Martian equator, in the middle of Arabia Terra, the most extensive region of the transition zone between the low northern plains and the southern cratered highlands. Taken on May 9, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and cropped to post here, the photo shows some layered mesas surrounded by a terraced and scalloped terrain with dust filling the low spots.

This is likely to be a very dry place on Mars. At only 2 degrees north of the equator, the evidence so far suggests that if there is a buried ice table (like the water table on Earth), it will be much deeper than at higher latitudes. The terrain reflects this, looking reminiscent of Monument Valley in the American southwest. In fact, the satellite image below, which I grabbed from MapQuest, shows a typical mesa in Monument Valley.
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Coronavirus update

February 15, 2020 10:40 am Robert Zimmerman

This article about the coronavirus epidemic (the virus is now officially dubbed Covid-19) focuses initially on how the Chinese are even quarantining bank notes in their effort to stem the disease’s spread.

I instead found this quote farther down the page much more significant:

More than 1,380 people with the virus are now confirmed to have died and more than 64,400 have been infected in at least 28 countries and regions.

The death rate of the disease, even as it has grown, remains about 2%. While tragic, this number suggests this hardly has the makings so far of a worldwide catastrophe. If anything, it appears to be about as deadly as the flu, which isn’t something to take lightly but also does not warrant any need for panic or desperation. The flu in the 2017-2018 season in the U.S. infected an estimated 45 million, killing about 61,000, a far lower death rate but impacting far more people. Like the flu, Covid-19 appears to be more deadly to older patients.

This epidemic needs to be taken seriously, but it so far does not justify any panic.

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Weird glacial features in Martian crater

October 3, 2019 1:47 pm Robert Zimmerman

Click for full image.

Cool image time! In reviewing today’s October release of new images from the high resolution camera of Mars Reconnaissance Orbiter (MRO), I came across the strange geology shown in the image to the right, rotated, cropped, and reduced to post here.

The uncaptioned image calls these “glacial features within crater.” The crater is located at 35 degrees north latitude in Arabia Terra, one of the more extensive regions of the transition zone between the northern lowlands and the southern highlands. It is also located within the northern band from 30 to 60 degrees latitude where most of the buried Martian glaciers are found.

The most abundant type of buried glaciers are called concentric crater fill (CCF) because they are found inside craters, and often show decay in a concentric manner. This weird feature likely falls into that category, though I would hardly call these glacier features concentric.

I’m not even sure if this is an impact crater. If it is, its rim has been heavily obscured, making it look instead like an irregular depression with one outlet to the south. In fact, I suspect it is possibly one of the lakes that scientists believe pepper this part of Arabia Terra and might have contained liquid water two to three billion years ago. That water would have later frozen, and possibly become covered by dust and debris to protect it.

According to present theories, Mars is presently in a period where its mid-latitude glaciers are shrinking, the water sublimating away and being transported back to its poles. The weird formations here suggest this process. Imagine what happens when you spray warm water on a big block of ice. It dissolves, but randomly to form weird shapes.

In this case the glacier is shrinking randomly where the ice has gotten exposed. In the thin Martian atmosphere, it transitions directly from a solid to a gas, sublimating into the atmosphere to leave these inexplicable shapes.

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Is it a volcano or an impact crater? Mars Express wants to know!

April 13, 2018 9:58 am Robert Zimmerman

Europe’s Mars Express orbiter has taken a high resolution image of Ismenia Patera, a very large crater located in the Arabia Terra region of Mars, the largest part of the transition zone between the low flat northern plains and the high rough southern terrain.

The crater is intriguing to scientists because they are not sure if it was created by an impact, or a volcano.

Certain properties of the surface features seen in Arabia Terra suggest a volcanic origin: for example, their irregular shapes, low topographic relief, their relatively uplifted rims and apparent lack of ejected material that would usually be present around an impact crater.

However, some of these features and irregular shapes could also be present in impact craters that have simply evolved and interacted with their environment in particular ways over time.

There is also additional evidence that this region was once home to volcanic activity. If so, that activity would have changed the terrain, and thus made its geological history more complex and difficult to decipher, a fact that is important since this is also a region that might have been at the edge of theorized northern Martian Ocean.

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