Tag: geology

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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on April 12, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists simply label as “Northern Mid-latitude Terrain”.

I have focused in on that meandering channel and the landscape around it. On Earth we would assume that channel marks the drainage of a river or stream, possibly also shaped by a glacier at some point because of its U-shaped profile. This guess is strengthened by the elevation data from MRO, which shows the channel descending to the southwest about 440 feet along its 2.2 mile length.

The channel and the eroded look of the surrounding terrain suggests strongly the presence of near-surface ice at this location, which is not unreasonable based on its 32 degree north latitude. The wider look below only adds further strength to this hypothesis, but also adds a lot more details explaining the genesis of this strange landscape.
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Today’s cool image could be labeled a “What the heck?!” photo, as the origin of its most distinct feature is utterly baffling. The picture to the right, cropped, reduced, and sharpened to post here, was taken on June 18, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what look like a collection of meandering ridges peeking out from a terrain covered by thick dust.

The scientists label this dust-covered ground, as well as the ripple dunes to the south in the full image, “sand sheets.” Without question, the ground here seems to resemble a Sahara-like terrain. It is utterly featureless, other than the few bedrock features that poke up out of that sand. In the full image some peaks stick out, but it the meandering ridges in this section that are most intriguing. They are reminiscent of rimstone dams in caves, but what formed them remains baffling, since cave rimstone dams are formed by the interaction of limestone and water, and there is absolutely no evidence of any near surface ice at this location in the dry equatorial regions of Mars.

All the ridges signify is a buried terrain formed in some inexplicable way.
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Today’s cool image is actual one new picture and four past images, which taken together reveal something about the larger wind patterns on Mars. The picture to the right, cropped, reduced, and sharpened to post here, was taken on June 27, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and shows a tiny wind-swept section of the giant volcanic ash field dubbed the Medusae Fossae Formation, about the size of the subcontinent of India and thought to be source of most of the dust on Mars.

The innumerable parallel thin ridges here all suggest that the prevailing winds blow from the southeast to the northwest. As they blow, the scour the surface ash out, and sometimes reveal the underlying bedrock, which here shows up as those small peaks and a handful of northeast-to-southwest trending larger ridges. Note too that the picture shown is only a small section of the full image, which shows that this landscape continues for a considerable distance in all directions.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on April 10, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows an unnamed 1.2-mile-wide crater at about 35 degrees south latitude with what appears to be residual glacial ice hugging its north interior wall.

As this is in the southern hemisphere, the ground immediately below the south-facing interior wall of the crater is going to be in shadow the most, and thus it will also be the place where any surface or near-surface ice will survive the longest. In this case it appears that from the bumpy nature of that residual ice it has also been sublimating away. Within it however remains the faint hint of multiple layers, suggesting about a dozen past climate cycles with each new cycle producing a new but smaller layer with less ice.

The material in the southern half of the crater floor appears to be dust formed into ripple dunes.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on May 13, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists call a “channel and depression”, though to my eye everything looks like flow channels, descending to the east.

The drop from the narrow northern channel to wider southern channel is about 200 feet, with the small crater on the left sitting about halfway between. To our Earthbound eyes, something clearly flowed downhill from that northern channel into the wider channel. What we don’t know now is what the material was that did the flowing?

Was it liquid water? Glaciers? The overview map below provides some context, though it doesn’t actually provide an answer.
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Today’s cool image to the right, cropped, reduced, and sharpened to post here, provides us a glimpse at the lower mid-latitudes of Mars where the terrain is beginning to dry out as we move south. The picture was taken on April 29, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what the scientists label “large linear features.”

The main north-south ridge is only about 20-25 feet high, and its meandering nature (which can be seen more clearly in the full image) suggests it is possibly an inverted channel, formed when the bed of a former canyon gets compressed by the water or ice that flows through it, and when the surrounding terrain gets eroded away that channel bed becomes a ridge.

These ridges however could also possibly be volcanic dikes, where magma had pushed up through fractures and faults to form these more resistant ridges.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on June 22, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as “The tip of Cerberus Fossae,” a thousand-mile-long crack in the surface of Mars formed when the ground was pulled apart by underground forces.

If you look closely at the picture’s right edge, you can see that beyond the end of the fissure it actually continues but appears filled with material. In the full picture this however is the end of the crack. Beyond this point the ground is as smooth and as generally featureless as seen within the picture itself, and as also shown in this MRO context camera view of the same area.

Cerberus Fossae is actually three parallel cracks, with this the northernmost one. The eastern tip of the middle crack was previously highlighted in a cool image in July 2022.
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Of all many cool images I’ve posted, today might take the cake (pun intended) for the best illustration of the alien nature of Mars. The picture to the right, cropped, reduced, and sharpened to post here, was taken on June 28, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what the scientists simply label as “flow features.”

I personally don’t see any obvious flow features in the full image, unless one wants to call the brain terrain that covers this entire plain a flow feature. Brain terrain is a feature unique to Mars whose origin remains a mystery to geologists. As noted by scientists in captioned MRO image in 2019:

You are staring at one of the unsolved mysteries on Mars. This surface texture of interconnected ridges and troughs, referred to as “brain terrain” is found throughout the mid-latitude regions of Mars.

…This bizarrely textured terrain may be directly related to the water-ice that lies beneath the surface. One hypothesis is that when the buried water-ice sublimates (changes from a solid to a gas), it forms the troughs in the ice. The formation of these features might be an active process that is slowly occurring since HiRISE [MRO’s high resolution camera] has yet to detect significant changes in these terrains.

The wedding cake inside the small crater to the upper right only adds to the alienness of this terrain.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on July 3, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Dubbed a “terrain sample” by the camera team, it was likely taken not as part of any scientist’s specific research program but to fill a gap in the camera’s schedule in order to maintain its proper temperature. When the camera team needs to do this they try to pick something of interest that is below during that gap.

In this case MRO was over the vast flood lava plains of Mars where for many hundreds of miles the only features are small variations produced from different overlapping lava flood events. The layers of lava in this region in fact appear so thick that there are relatively few places where the older topography still sticks up through the lava. In the case of this picture, the ridges might indicate such buried topography, but they also might simply be dikes of lava, pushed up through fissures from underground.
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