Tag: geology

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Cool image time! The picture to the right, cropped, reduced, and enhanced to post here, was taken on May 14, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as a “layered butte inside small crater.”

The crater is only about 1.8 miles across, and is only a couple of hundred feet deep, at the most. Because this crater sits on a large slope rising to the southwest, the mesa’s peak is actually about thirty feet higher than the crater’s northern rim, but is still below the southern rim by about 70 feet.

A close look at the mesa’s slopes suggests about a dozen obvious layers, though based on data from the rovers Curiosity and Perseverance, those obvious layers are probably divided into many hundreds of thinner layers in between.

What caused these layers? And how did such a small crater get such a relatively large mesa in its center? As always, the overview map provides some clues, but as always it does not provide a definitive answer.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on April 5, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I have cropped it to focus on the geological feature that likely attracted the interest of the scientists who requested this photo, the mesa that has a ridgeline running over it as if the mesa was not even there.

The mesa is about 80 feet high on its west side, but on its east the ground continues to drop away more than 500 feet as you move 2.5 miles to the east. Based on how the MRO science team interprets the colors [pdf] in the color strip, the orange areas are likely dust while the greenish surface suggests coarser sand and boulders. This conclusion is reinforced if you look at the parallel dunes south of the mesa. The dunes are yellow-orange (dust) while the ground between is yellow-green (sand), exactly what you expect with the larger coarser material settling in lower elevations.

The overview map provides the context, which might help explain the ridgeline.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on March 18, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

This is one of what I like to call “What the heck?” images. The broken up blocks resemble ice floes on the edge of the Arctic ice cap that have broken off and have begun floating away.

The problem with this theory is many fold. First, this is on Mars and not on Earth. Second the “sea” these blocks are supposedly “floating” in is actual solid lava. There is no water or ice here, on the surface or even underground. This is in the dry tropics of Mars, where little or no near-surface ice has so far been detected.

The overview map below provides some context, and possibly an explanation.
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Cool image time! The picture above, cropped, reduced, and sharpened to post here, was taken on April 18, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a gully that cuts down from the western rim of a 21-mile-wide unnamed crater in the southern cratered highlands of Mars.

The small rectangle on the overview map to the right marks the location, with the inset providing a close-up of this crater, with the white bar indicating the area covered by the photo above. The overall elevation loss from the rim on the left down to the crater floor on the right is about 3,800 feet.

The first high resolution picture of this gully was taken in 2016, with subsequent pictures taken in 2021 and 2022. In comparing the newest picture above with the 2016 photo I can detect no changes, but I am not looking a the highest resolution available. In addition, both of these pictures were taken during the Martian spring. The 2021 and 2022 pictures were taken during the Martian summer, and in both the north-facing wall where the gully is beginning to narrow seemed brighter.

It is likely the researchers are looking to see if any frost — either ice or dry ice — appeared during the winter and then sublimated away in the summer. Such a change could cause some of the erosion that produced this gully.

For the original images go here and here.

Today’s cool image is actually a comparison of two different high resolution images from Mars Reconnaissance Orbiter (MRO), both of which illustrate why it is very dangerous to come to any conclusions about such images without knowing a lot more about them.

The top image to the right, cropped to post here, was a terrain sample image taken on March 30, 2024. Such images are usually taken not to complete any particular research project, but are taken to fill a gap in the schedule in order to maintain the camera’s proper temperature. When the camera team has to do this, they attempt to pick a spot that might have some geological interest. Sometimes they get something surprising. Often however the features in the picture are boring.

In this case they spotted a place where the ground appears appears to be eroding away in a random pattern.

The bottom image, cropped, reduced, and enhanced to post here, was taken on March 24, 2024 and was part of planned research. It shows a section of the Martian south ice cap, specifically the area where scientists believe there is a residual permanent small cap of dry ice on top of a thick underlying water ice cap.

Like the top image, the features here suggest some sort of erosion process eating away randomly at the ground’s upper layers.

The two images illustrate the difficulty of interpreting orbital images. At first glance the geological features of both appear very similar. Yet the top image is located in the very dry equatorial regions of Mars, and in fact is inside the Medusae Fossae Formation, the largest field of volcanic ash on the red planet. The layers here are likely ash, and the erosion that carved out the hollows likely came from wind. If there ever was near-surface ice at this location, it was many eons ago.

The bottom image however likely shows the sublimation process that is slowly eating away at the residual dry ice cap at the south pole. The Martian north pole does not have residual permanent cap of frozen carbon dioxide, and the reasons why the two caps are different in this way are complex and not completely understood.

Both images show erosion that produces features that look similar. But the materials involved and the causes are completely different.

Remember this when you look at any orbital picture taken of Mars, or any other planetary object. Without the larger context (location, make-up, known history), any guess about the nature of the features there is nothing more than a wild guess, no different than throwing darts at a wall while wearing a blindfold.

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Cool image time! The picture to the left, cropped, reduced, and sharpened to post here, was taken on April 25, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

It shows what the science team labels a “scour pit island,” an area about 13 miles long and 3.5 miles wide where the ground is covered by these pits.

Your eye may play tricks on you, reversing the elevations. These are all pits, with most having a central peak or ridgeline. To help, note that the sunlight is coming from the west. The arrow on the center left of the picture sits on a plateau above these pits.

According to this paper [pdf], the pits are slowly dug out by the wind coming from the southeast blowing to the northwest, as indicated by the arrows. The central peaks or ridges are thought to be a hint of the original topography, with the wind only able to pull ash from the terrain around these peaks.
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For original images go here and here.

Today’s two cool images above provide a nice sense of the massive nature of many Martian landslides. Scientists often call this kind of slide “mass wasting,” because rather than it occurring because a single rock propagates a larger flow of rocks as it starts rolling downhill, this slide occurs because a large section of the hillside suddenly breaks free and moves downward as a unit, carving a path as it goes.

Mars has a lot of these kinds of slides, likely caused partly by its lower gravity, 39% that of Earth’s.

The overview map to the right marks the location of both slides by their numbers. Number one took place on the eastern interior rim of a 56-mile-wide and 7,000-foot-deep unnamed crater the dry tropics of Mars. The slide dropped about 3,000 feet, beginning about halfway down from the top of the rim and not quite reaching the crater floor. The picture was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on March 31, 2024.

Number two occurred on the western interior rim of a 32-mile-wide and 6,500-foot-deep unnamed crater in the mid-latitudes where near-surface ice and glacial features are often found. In this case the slide fell downward about 3,500 feet. The picture was taken by MRO’s high resolution camera on March 14, 2024.

Despite the different latitudes and thus different climates and geological settings, both landslides look similar. It is possible they occurred under similar conditions, but at very different times. Or it is also possible that the Mars gravity and general environment promotes these mass wasting events everywhere.

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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on April 25, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The scientists label this layered deposits, but that hardly describes what we are looking at. This slope, as shown in the overview map above, is the north flank of the central ridgeline inside the giant enclosed canyon depression dubbed Hebes Chasma, located just north of the main canyon of Valles Marineris, the largest known canyon in the solar system.

From floor to peak the ridge is around 16,000 feet high. Yet, its peak sits more than 6,000 feet below the plateau that surrounds Hebes. In this one picture the drop from high to low is only 5,700 feet, with thousands of feet of cliff unseen below and above.

Yet every single foot of these gigantic cliffs is layered. Based on close-up data obtained by Curiosity on the slopes of Mount Sharp in Gale Crater on the other side of the planet, the layers we can see here only represent the most coarse sedimentary boundaries. Within these layers are likely thousands upon thousands of thin additional layers, each likely representing some cyclical climate proces on Mars, even down to individual years.

Note too that the lower slopes in this picture (near the top) suggest some form of erosion flowing downhill. What caused that erosion process however remains unknown. It could have been liquid water, or glaciers, or some other process unique to Mars that we still haven’t uncovered.

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Today’s cool image is another example of how little we really understand the geology of Mars. The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken on February 22, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The focus of the image is the eastern end of a large and very distinct dune field inside 31-mile-wide Matera Crater, as shown by the white rectangle in the overview map above. The field fills an area 10 by 11 miles inside the floor of the crater. On that eastern end is a very pronounced drainage gully dropping downhill about 2,000 feet to the east.

Gullies on Martian slopes, especially on the interior rims of craters, are not unusual. Though their true cause is not yet confirmed, the theories behind their existence all relate to some form of water/ice process, mostly relating to the seasonal freeze-thaw cycle.

This picture was taken in the spring, exactly when seasonal changes might be spotted. In fact, scientists have been taking regular MRO images of this gully since 2007, when it was featured image. From that 2007 caption:
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on February 26, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as the “relation between flutes and flows”.

The flood lava plain in the northern part of this picture represents the flows. At some point in the distant past some event, either a volcanic eruption, or a large impact, caused lava to spew out across this terrain, leaving behind a smooth plain that has only partly been marked by later crater impacts.

The many parallel ridges pointing to the northeast in the southern part of the picture represent the flutes.

One other very important flow is not directly visible. The prevailing winds that blow to the southwest are what carved these flutes, slowly pushing the material southward while carving out the many gaps between the ridges.
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Sometimes the cool geological features I find in the Mars Reconnaissance Orbiter (MRO) image archive are so large they are difficult to present on this webpage. Today is an example. The picture to the right, cropped, reduced, and sharpened to post here, was taken on March 13, 2024 by the high resolution camera on MRO. It shows the distinct run-out of debris from a landslide that flowed downhill to the north as a single unit of material. Along the way it carved its track in the ground, almost like a ramp.

The full picture however suggested something much more spectacular. In that full image this landslide is merely a small side avalanche to a landslide many times larger. And that high resolution picture only shows what appears to be a small section of that giant slide. Obviously, this required a look at the global mosaic produced by MRO’s context camera to find out how far that avalanche actually extended.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on February 10, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label boringly “Lava Interactions with Landscape.”

What is the lava, and what is the landscape? Here’s is my initial guess, based simply on looking at this image alone. The mound in the middle is the landscape, the rounded top of a very ancient mountain or hill. The flat plain that surrounds it is flood lava, that in the far past poured in and mostly buried the mountain.

Everything here signals a very old terrain. To get this mountain worn so smooth from the thin Martian atmosphere has to have taken more than a billion years. And that flood lava has to also be as old, because of the number of craters on its surface. I don’t know the impact rate, but I know it takes time to accumulate this number of impacts.

The sense of age is further underlined by the moat that surrounds the hill. When that lava poured in, it would have flooded right up to the mountain slope. Over time the weakest section of lava, most prone to erosion, would be that contact point. To wear it away as we now see it must have taken many eons.

All these speculations are a very unreliable guesses. To get a better understanding of this terrain it is essential we look at more than this picture alone.
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Cool image time! The picture to the right, rotated, cropped, and enhanced to post here, was taken on December 17, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label “banded terrain and possible breached crater.”

Banded terrain is another name for a geological feature dubbed “taffy terrain” and only found on Mars, and furthermore only found there in Hellas Basin, the deepest giant impact basin on the red planet. This taffy terrain is considered very young, no than 3 billion years old, and formed from the flow of some form of viscous material, though what that material is remains unsolved.

This image however may help solve that mystery. The breached crater is just off frame to the upper right. The two-fingered flow coming down from the picture’s top is the flow coming out of the crater’s gap.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on February 25, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small spot of the floor of Mars’ giant canyon Valles Marineris, the largest such canyon known in the solar system, as indicated by the white dot on the overview map above.

This location is not actually at the very bottom of the canyon, but on a very large mountainous bench extending out about 20 miles from the canyon’s south rim. It seems there is a lot of dust and sand on this bench, producing many miles of swirling dunes. It also appears there are many terraced layers in the region as well, which also swirl in curves going in many different directions. Though it appears that most of the swirls in this picture are from layers in the bedrock, this conclusion is not certain. For example, are the curves on the top of the mesa dunes or bedrock layers? The answer is hardly clear.

For scale, the canyon at this location is about 80 to 90 miles wide. The northern rim rises five miles from the bottom to the top, while the south rises seven miles. And yet, though five to ten times larger than Earth’s Grand Canyon, this is only a small side spur of Valles Marineris.