Tag: geology

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Today’s cool image could also be entered into my “What the heck?!” category of strange Martian geology. The picture to the right, cropped, reduced, and sharpened to post here, was taken on October 19, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels this as “Round Deposits in Crater.” And yup, that’s what we have, round and flat small mesas inside an unnamed 3,500-foot-wide very shallow crater (no more than 10-20 feet deep) that also appears to be sitting higher than the surrounding landscape. Furthermore, several nearby craters are also raised, with one having its own oblong flat interior mesa. Moreover, the terrain around the crater appears stippled, as if it has been eroding or sublimating away.

The latitude, 37 degrees north, provides the first clue for explaining this weird landscape.
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Just because there are no new images coming back from Mars at this time because the Sun is in the way does not mean we can’t enjoy more cool Martian images. The picture to the right, cropped, reduced, and sharpened to post here, was taken on October 20, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

Labeled merely a “terrain sample,” this means it was taken not as part of any particular research project but to fill a gap in the camera’s schedule. The camera team needs to take regular photographs in order to maintain the camera’s proper temperature, and when there is a long gap they add a terrain sample image to the schedule. Usually they try to pick some target of interest.

In this case the target is this 2,500-foot-high cliff, in which we can see a whole range of Martian geological mysteries. First there are the slope streaks on the cliff, a feature unique to Mars but as yet unexplained. Resembling avalanches, these streaks leave no debris piles at their base, do not change the topography in any way, and can appear randomly throughout the year, fading with time. Though the streaks in this picture are dark, streaks can also be bright.

Both the parallel ridges at the base of the cliff, as well as the cliff itself, are remnants of other major geological events, at least based on present theories.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on October 24, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels this simply as “irregular terrain.” It is far more than that. We are looking at a three-mile-wide shallow canyon, with what appear to be eroding glacial features on the canyon floor.

The location is at 35 degrees north latitude, so finding glacial features here is entirely unsurprising, especially because this location is the southern edge of the 2,000-mile-long mid-latitude strip in Mar’ northern hemisphere I label glacier country, because almost every picture shows such glacial features.

In this case, the channel also suggests a much more complex geological history, that could involve flowing water though flowing glaciers are increasingly becoming an alternative explanation.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 9, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labels “an inverted channel.” From the caption:

Topographic inversion is a process where geologic features that were once low-lying, like impact craters or riverbeds, become elevated over time, like mesas or ridges. In this process, a crater or channel is filled with lava or sediment that becomes lithified [hardened]. If this infill is more resistant to erosion than the surrounding landscape, the less-resistant material can be eroded away by wind or water. The former crater or valley fill, being more resistant, remains elevated as the landscape around it lowers. The original low-lying feature becomes a mesa or ridge.

In this image, an ancient river network and nearby impact craters have undergone topographic inversion. Impact craters contain round mesas within them, and the stream channel is defined by a network of ridges.

The location of this inverted channel makes its history even more interesting.
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Cool image time! On October 7, 2025, the science team that operates HiRISE, the high resolution camera on Mars Reconnaissance Orbiter (MRO), took its 100,000th picture since entering Mars orbit in March 2006.

The objective of this observation is to better resolve sand dunes and the rocky material underneath them. These dark, eroded rocks may be the source for some of these Syrtis Major sand dunes. Our image was suggested by a high school student enrolled in the Jefferson County Executive Internship program in Colorado in 2023, one of many public outreach programs the HiRISE Team engages in.

To celebrate this accomplishment and the fantastic geology of the scene, students and staff in the HiRISE Photogrammetry lab constructed this digital terrain model. This oblique image highlights the hummocky mounds of the plains that border Jezero Crater, which are among the oldest on Mars.

That oblique image, cropped, reduced, and sharpened to post here, is to the right. The location is about 50 miles to the southwest of Jezero Crater where the rover Perseverance landed.
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Cool image time! The picture to the right, cropped, reduced, sharpened, and annotated to post here, was taken on October 27, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I have also rotate the image so that north is to the top.

The science team labels this “Exposure of North Polar Layered Deposits,” an apt description of the horizontal red and grey and blue layers that dominate the image and make this geology look more like an abstract painting than a natural landscape. What we are actually looking at is a canyon 800-to-1,200 feet deep within the north polar ice cap of Mars.

The picture was taken in the summer with the Sun about 12 degrees above the horizon to the south. Thus, the northern cliff face is illuminated, revealing its many colored layers, while the south face is mostly in shadow, hiding those layers.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on October 27, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels this a “twisted surface,” to which I think we all can agree. What we are looking at is a geological feature found only on Mars in only one region that has been labeled “taffy terrain” by scientists. According to a 2014 paper, the scientists posit that this material must be some sort of “a viscous fluid,” naturally flowing downward into “localized depressions.” Because of its weird nature I have posted many cool images of it in the past (see here, here, here, here, here, and here).

In the case of the image to the right, the red dot marks the peak of a small knob, with the green dot on the upper left the low point about 900 feet below. As you can see, the taffy has migrated into the depressions, as some flowing material would.
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Cool image time! The picture to the right, cropped, reduced, and enhanced to post here, was taken on October 28, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled by the science team as “mottled ridged terrain,” it shows a relatively flat area of scattered broken-up flat-topped ridges and knobs, following no clear pattern of formation.

In trying to research this, I could only find one paper [pdf] discussing this kind of mottled ridges that did a survey of similar features across a large region to the northwest. That paper could not determine what caused such features, but came up with hypothesis. From the abstract:

While it is not possible to determine the precise formation mechanism of these polygonal ridge networks from our new data, their formation can be assessed in terms of three possibly separate processes: (1) polygonal fracture formation, (2) fracture filling and (3) exhumation. We find that polygonal
fracture formation by impact cratering and/or desiccation of sedimentary host deposits is consistent with our results and previous spectral studies. Once the polygonal fractures have formed, fracture filling by clastic dikes and/or mineral precipitation from aqueous circulation is most consistent with our results. Exhumation, probably by aeolian processes that eroded much of these ancient Noachian terrains where the ridges are present caused the filled fractures to lie in relief as ridges today.

To put this in plain terms, the initial polygon-patterned cracks were formed by either an impact or the drying out of the surface (similar to the cracks seen on dried mud here on Earth). Both could have contributed. Then material welled up from below, either lava or mud, that hardened to fill the cracks. Later erosion by wind stripped away the surface, leaving behind these broken ridges.

As always, the location adds some very interesting context.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 26, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The scientists label this image “Moraine-like assemblage exposed by ice retreat.” I say: If anyone still doubts the extensive presence of near-surface ice on Mars, this picture should put that doubt to rest.

The white dot on the overview map above marks the location, deep within the 2,000-mile-long strip in the Martian northern mid-latitudes that I label “glacier country,” because practically every picture taken there shows glacial features. This picture is just one more example. As the inset in the overview above shows, this flow is coming down from the exterior rim of an unnamed, partly obscured ancient 17-mile-wide crater, dropping about 7,000 feet from the rim’s peak. This particular section shows the last 3,000 feet of that descent, as the glacier worked its way through a gap in a ridge paralleling that rim.

The image label refers to the flow features that appear to be corroding away. It appears the full data set suggests that corrosion is exposing the material pushed downward by that glacier, what on Earth we call a moraine.

New data using the Sharad radar instrument on Mars Reconnaissance Orbiter (MRO) appears to disprove the 2018 observations that suggested a lake of liquid water might exist under the Martian south pole ice cap.

From the abstract:

Due to a novel spacecraft maneuver, SHARAD has now obtained a basal return associated with the putative body of water. Modeling of the radar response is not consistent with the liquid water explanation, instead suggesting a localized, low roughness region of dry rock/dust beneath the ice could explain the SHARAD response. Reconciling the divergent responses of SHARAD and MARSIS remains essential to determine the nature of this anomalous south polar region.

In other words, this reflectively bright area is caused not by liquid water, but by a very smooth patch in the south pole’s many underlying layers. What remains unknown is the cause of that smoothness. The scientists posit that “a crater floor with sediment or impact melt fill” could be the cause. Another study in 2022 suggested it could be volcanic rock, while a 2021 study claimed clay could be the cause.

At the moment no one has the ability to find out. The only certain way would be to drill deep cores, but that won’t happen until there is a thriving colony on Mars.

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Cool image time! The picture to the right is taken from a global mosaic created from images taken by the wide-view context camera on Mars Reconnaissance Orbiter (MRO). The original source image was probably a photograph taken on February 15, 2020.

I normally begin with an image from MRO’s high resolution camera, but the only images that camera took of this crater did not show it entirely. This context camera shows it in all its glory, what to my eye appears to be one of the weirdest craters I’ve seen on Mars.

First, note its oblong shape — 5.5 miles long and 3.7 miles wide — which appears to narrow to the southeast. It certainly appears that if this crater was caused by an impact, the bolide came in at a very low angle from the northwest, plowing this 700-foot-deep divot as it drove itself into the ground. Research has shown that an impact has to come in almost sideways to do this. Even at slightly higher angles the resulting craters will still appear round.

But wait, there’s more!
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 20, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The camera team describes these features as “ridges,” which in one sense is entirely true. The features are ridges that rise above the surrounding plain. The problem is that they are also cracks, with most showing a distinct central fissure in their middle.

Such double ridged cracks are reminiscent of the surface of dried mud or paint, when it begins to crack and shrink. The surface on each side of a crack pulls away, rising upward slightly as it does so. Is that what we are seeing here, the drying of this surface?

As always, location is critical to understanding the Martian geology.
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Cool image time! The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken on September 24, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels this as an “avalanche scarp”. At first glance it appears we are looking at a major mass wasting event flowing downward to cover the lighter banded terrain near the bottom of the picture.

The problem is that the overlying material didn’t move as an avalanche down onto that lighter material. Note that it has within it its own layers. To have flowed over that lower terrain it would have had to do that coherently, its many layers moving in unison. This doesn’t seem probable, though who knows considering the alien nature of Mars.

So what is going on? And why was this picture taken?
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