Tag: geology

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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on June 23, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label “branching deposits,” two wiggling ridgelines with other ridges branching off from them.

What caused this? On Mars there are many such meandering ridges, all of which look like rivers that have positive relief, the opposite of what you would expect. The theory is that these weaving ridges were once canyons where either water or ice once flowed, compacting the streambed so that it was more dense than the surrounding terrain. When that terrain eroded away it left that streambed behind, as a raised meandering ridge.

That answer however might not apply here.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 13, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

In this one picture can be seen a glimpse of the entire history of the numerous lava eruptions that once dominated Mars when its giant volcanoes were active one to three billion years ago. The three aligned craterlike depressions likely signal the existence of a large lava tube below ground, placed there during an early large eruption, when the volcano was spewing out so much flood lava that such large tubes could form. The smaller meandering surface rills signal later eruptions that carried less flood lava and thus produced a smaller drainage features.

And finally, the rough and cracked appearance of the surface indicates the ancient age of those last eruptions, probably laid down about a billion years ago. Since then, the volcano has been dormant, and the frozen lava here has had time to erode, become roughened, and show signs of slowly wearing away.
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Cool image time! It is always dangerous to come to any quick conclusions about what you see from pictures from another planet. The photograph to the right, rotated, cropped, reduced, and sharpened to post here, was taken on August 19, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what at first glance looks like a surface similar to frosting seen on window panes on Earth in the winter, where water condensation freezes to form crystalline patterns.

Your first glance would be wrong. This terrain is about 120 miles north of the Martian equator, placing inside the dry equatorial regions where no near-surface ice is known to exist. If this geological feature is formed by the same condensation processes that create ice frost, then it must involve the deposition of some other type of material.

The explanation would also have to account for the change in the terrain, from finely patterned on the right to more crystalline on the left.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on March 15, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The white dot on the overview map above marks the location, on the west end of the 2,000-mile-long northern mid-latitude strip I label glacier country because almost every image suggests the presence of ice and glaciers.

Where this crater is located the terrain is shifting from mesas and criss-crossing canyons to the northern lowland plains. Thus, the features that suggest the presence of ice shift from glacial in nature (flowing down hollows and cliffsides or within canyons) to that of a near-surface ice sheet, which acts to distort impact craters and leave large splash aprons around them.

The straight depression cutting into the crater near the center top that is also aligned with craters to the southwest suggests that these craters are either sinkholes into a void created by a fault line, or the impacts all occurred at the same time, as the asteroid broke up while cutting through the Martian atmosphere.

Either could be true. The data is insufficient to determine which.

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Today’s cool image not only shows us some puzzling lava terrain on Mars, it highlights the continuing camera problems on Mars Reconnaissance Orbiter (MRO) that began last month and now appear to be permanent.

The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 29, 2023 by the high resolution camera on MRO. The black strip through the middle of the picture highlights MRO’s ongoing problem, as described by the science team in its monthly download of new MRO high resolution pictures:

The electronics unit for CCD RED4 started to fail in August 2023 and we have not been acquiring images [data] in this central swath of the images. The processing pipelines will be updated to fill this gap with the IR10 data for some products. The 3-color coverage is now reduced in width.

The picture shows the failure of this electronics unit. The color strip is now only about half as wide as normal, with the other half the black strip with no data. As the problem first appeared in July, and remains unresolved, it probably is permanent. Though MRO’s high resolution camera can still produce images, they will be less useful, their center strip blank.

This failure should not be a surprise. In fact, it is remarkable that so little has gone wrong with MRO considering its age. The spacecraft was launched in 2005, entered Mars orbit in 2006, and has been working non-stop now for about seventeen years. Moreover, it was built in the early 2000s, making it almost a quarter century old at this point. How much longer it can survive is an open question, but a lifespan of twenty years is usually the limit for most spacecraft. The Hubble Space Telescope however gives us hope MRO can last longer, as Hubble has now been in orbit for 33 years, and continues to operate.

Despite this data loss, the picture still shows some intriguing and puzzling geology
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on June 22, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The white spot near the center of the overview map above marks its location, deep inside the 2,000-mile-long region in the northern mid-latitudes I call glacier country, as everything there seems covered with glacial features of some kind. All the features in this picture are smaller than 50 feet high, based on the resolution of the topographical data obtained by Mars Global Surveyor in the 1990s.

What makes this picture interesting are the layers, made most obvious in the terraced mesa in the upper left. Surrounding this mesa for dozens of miles in all directions are similar layered features, all suggesting that the glacial ice sheets that appear to coat this region have either have been sublimating away over time, or when growing grew less with each subsequent growth cycle.

Though both have or are likely happening, the latter most likely explains the terraces, as there is a lot of evidence on the surface of Mars showing that each subsequent growth cycle produced smaller glaciers and ice layers.

From the perspective of future colonists, this picture once again shows that water will readily accessible on Mars, as long as you travel north or south of the equator at least 30 degrees of latitude. This location is at 42 degrees north, and is very typical of this whole region.

Circling the north pole of Mars is a gigantic dune field dubbed Olympia Undae, with its densest regions (marked in red on the overview map to the right) estimated to be 700 miles long and covering 120 degrees of longitude.

Where does all the sand come from that created this dune ocean? We now have a rough idea. The arrows on the map to the right indicate the direction of the prevailing winds, as recently determined by scientists studying the orientation of dunes. From this it appears that much of the dust comes from the north polar icecap itself, from its lower layers where dust and ice are cemented together. The prevailing winds, especially in the canyons that cut into the icecap, drive that dust out from the lower layers, where it over eons has piled up in that circular ocean of sand.

The white cross marks the location of today’s cool image, an attempt by scientists to photograph at high resolution one of the sources of this sand, on the edge of the icecap.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on July 6, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

This 500-to-600-foot-high hill represents what is likely the top of a much larger mountain, now buried by the flood lava that surrounds it. The edge of that flood lava can be seen best along the base of the hill’s northern slope, where this now hardened lava had washed up against that slope.

That this Martian mountain is very old can be discerned from two features. One, it had to have been there when the lava flowed, and scientists estimate these lava flows are at least one billion years old. Second, peak’s rounded shape and eroded edges (showing terraced layers) suggest it has been here for far longer, allowing Mars’ thin atmosphere and climate to weather it down.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on June 30, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The scientists label it “Mesas in shallow trough,” but that is only describes a small part of what can be seen here, as I interpret it.

The picture itself shows a small portion of the floor of an unnamed 32-mile-wide crater, with the crater’s southeast interior rim beginning its rise in the lower right. First, note the meandering hollow in the upper left, suggesting some past flow. Second, note the pattern of small ridges on the flat crater floor, suggesting some past drying process that left cracks that later filled with material that formed the ridges at a later time. Third, the mesas themselves suggest chaos terrain, often formed on Mars in connection with glacial flows. Fourth, note that the trough which holds the mesas is on the edge of the crater floor, suggesting the trough and mesas mark the erosion that once occurred at the edge of some material, possibly ice, that once filled that floor.

The trough and small meander also signify something far larger that can only be seen when we zoom out.
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Cool image time! The picture to the right, cropped to post here, was taken on June 21, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The scientists label the strange tubelike features that are scattered throughout this picture as “landforms,” which is correctly vague because their origin is utterly inexplicable. The ground here is on the eastern slope of a small 20-mile-wide very flat shield volcano located about 150 miles northwest of the giant volcano Ascraeus Mons. The dark wind streaks point down that grade to the east, away from the shield volcano’s peak about 1,000 feet away. (If you look at the full image this indistinct peak is at dead center, with a linear depression (the volcano’s vent) beginning there and heading to the northeast for about four miles.)

Why these many tubes are all oriented in a northwest-southwest direction, at right angles to the slope, is baffling, especially because they hold to that same orientation all across the shield volcano, no matter the downward direction of the slope.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on June 28, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The intended science focus of the image is likely the floor of this canyon on the lower right, showing what appears to be a patch of uprised topography surrounded by what looks like glacial debris, which at this latitude of 39 degrees north is expected on Mars.

The grade at this location is downhill to the southwest, so if this is a glacier it is flowing in that direction.

The cliff is about 3,000 feet high, dropping that distance in about a mile and a half. Thus, this is only slightly less steep than the very steep cliff wall of the caldera of Olympus Mons, highlighted as a cool image two days ago.

What makes this canyon interesting — besides its spectacular scenery — is its larger context, recognized when one looks at this location from afar and thus sees how it shaped a vast portion of the global surface of Mars.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 14, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what appear to be horizontal layers in the inner wall of a small one-mile-wide and 150-foot deep unnamed crater on Mars. I have included the color version below, zoomed in to make those layers and their colors very clear.

As I have not contacted the scientists who requested this picture, I can only guess at its purpose. My guess however relates to those horizontal blue layers, reminiscent of the ice layers seen in Martian scarps at the high latitudes at about 50 to 55 degrees.

Normally it is rare to see horizontal layers like this in craters on Mars. Instead, what you usually see are downward-pointing gullies along with drainage and avalanche-type patterns, though the latter two might not be formed by either drainage or avalanches.

In this case these horizontal layers are clear and pronounced, making this crater a possibly important and somewhat unique find, based on its location.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on May 29, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labels an “unusual shaped hill” that is estimated to be about 20 to 40 feet high.

What makes it unusual? First, it sticks up out of the endless northern lowland plains for no obvious reason, though its shape suggests the existence of bedrock topography that is now buried by the dust and debris that coats the surface of those plains.

Second, the hill itself suggests that it formed after it was covered with debris. Note the crater near its northeast cliff. It appears that the cliff chopped off part of the crater, suggesting that the hill was once level with the surrounding terrain. Some later underground pressure pushed it upward, with its angled sides determined by existing faults.

Why those forces tilted the hill upward as it did, with only its eastern fringes raised, is a question a wide view might answer.
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Cool image time! Only yesterday I posted an image of polygons in the dry equatorial regions of Mars, where little evidence of near-surface ice is found and are thought to be the remnants from a long-dried lakebed.

Today we take a look at some polygons in the mid-latitudes of the icy northern lowland plains, where near-surface ice appears ubiquitous and as it sublimates away with the changing seasons causes all kinds of strange formations, including polygons.

The picture to the right, cropped, reduced, and sharpened to post here, is a good example, centered on a 0.6-mile-wide bright crater that appears to be filled with glacial ice. The image was taken on June 22, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and is located at 44 degrees north latitude on the western edge of Utopia Basin. As noted by the MRO science team in 2006 for a different MRO picture with similar features:
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on June 26, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team calls the features surrounding these small 20 to 60 foot high hills “polygon features,” an apt description and a geological feature that is seen in many places on Mars.

When these features are found in the icy higher latitudes, it is believed they are formed in connection to the freeze-thaw cycle that causes cracks in the near surface ice. When found in the dry equatorial regions, where these polygons are located, they are usually thought to be ancient evidence of past standing water that left behind these cracks, much like the cracks seen in mud after the water has evaporated away on Earth.

The formation of these tiny hills is a bit more complex.
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