A new global map of the near-surface ice on Mars

Global map of near-surface ice on Mars
Click for interactive map.

A project begun in 2019 to use all the presently available orbital data to compile a global map of the near-surface ice on Mars has now been released that global map, shown by the graphic above, taken from Figure 16.7 from the project’s science paper.

The various areas in blue show the evidence of ice down to about 5 meters, or about 15 feet, with darker blue areas indicated ice at greater depth. The study focused on latitudes below 60 degrees latitude, while also blocking out areas above one kilometer in elevation (as indicated in black on the map above). As the paper noted,
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The icy terrain near one of Starship’s prime candidate landing spots on Mars

The icy terrain near Starship's prime landing spot on Mars
Click for original image.

Cool image time! The picture to the right, cropped to post here, was taken on August 22, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The camera team labeled the picture a “terrain sample,” which generally means it was not taken as part of any scientist’s specific research request, but to fill a gap in the schedule so as to maintain the camera’s proper temperature. When the team needs to do this, they try to pick a location in the gap that might have some interesting features. Sometimes such pictures show relatively boring features. Sometimes the results are fascinating.

In this case the location chosen was in the northern lowland plains of Mars, in a region called Amazonis Planitia. At 38 degrees north latitude it is not surprising that the photo shows ice features. All the depressions here appear to have an eroding glacier, while the surrounding plateau resembles an untouched snow field in the very early spring, the snow beginning to sublimate away to leave the top rough and stuccoed. Note too that these depressions are likely not impact craters (they have no upraised rims and many are distorted in shape), but were likely formed by that same sublimation process.
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A low mid-latitude crater on Mars apparently filled to overflowing with ice

ice filling a Martian crater to overflowing
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on June 18, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a steep 1,000-foot-high cliff with what appears to be extensive glacial material at its base.

The many layers all suggest past climate cycles, where snow was deposited and the glacier grew, followed by a period when no snow fell and the glacier either shrank or remained unchanged. The terraced nature of the layers near the base of the cliff suggest that with each active cycle less snow was deposited and the glacier grew less.

The latitude is 33 degrees south, which puts it just outside the dry equatorial regions of Mars and inside the mid-latitude region where many such glacial features are found. Its closeness to the tropics however is significant, because by this point we should be seeing a diminishment of such features. Instead, the wider view shows us that the near surface ice in this region is extensive and in fact appears to cover everything.
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The fractured floor of the south Utopia Basin

The fracture floor of South Utopia Basin

Cool image time! The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken on August 5, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The central darker strip however comes from a September 27, 2008 image by MRO’s lower resolution context camera, inserted to fill in the blank section where one component on the high resolution camera has failed.

The picture focuses on what the scientists call a “pit interacting with a mound.” The 100-foot-deep pit is one of a very long meandering string of such pits, all of which suggest the existence of an buried river canyon into which debris is sinking. Altogether this particular string runs from several dozen miles, and its interaction with the triangular 300-foot-high mound suggests at first glance that the river that created the canyon did a turn to the left to avoid a large underground mountain, now mostly buried but revealed by its still exposed peak.

As is usual in planetary research, the first glance is often wrong. The overview map below provides a different answer, which says the formation of the aligned pits is related to the formation of the mound itself.
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Erosion revealing ridges on Mars?

Erosion revealing lava dikes on Mars?
Click for original image.

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 science team calls the features here “narrow ridges”, but what makes these criss-crossing ridges interesting is their location within the picture.

They appear only inside the hollows and depressions, as if erosion had stripped out a top layer of softer material to reveal these ridges, made of a harder material. The almost random but straight orientations of the ridges also suggest they formed along faults or cracks, which also suggests we are seeing dikes where lava was pushed up from below.

Whether the eroded softer material is lava or volcanic ash is unclear, though it certainly resembles the ash layers seen in the giant Medusa Fossae Formation ash field on the opposite side of Mars.

As always, a wider look helps clarify things.
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Location of mud volcanoes in Martian chaos terrain suggest past existence of mud lake

Mud volcanoes in the inland sea

Scientists mapping the location of mud volcanoes in chaos terrain in the dry equatorial regions of Mars have found numerous mud volcanoes, adding weight to the theory that an intermittent shallow lake once existed there.

The inset on the overview map to the right indicates the location of those mud volcanoes (of two types) in white and orange dots. What is significant is that none of the volcanoes are found on the mesas within this chaos terrain, only in the low flats below. From the caption:

Both feature types result from sedimentary volcanism – instead of magma upwells and eruptions, wet sediments, and salts reach and breach the surface, forming mounds and flows. Interestingly, these mounds only occur over the chaotic terrain floor materials and not on the mesas (red-shaded areas) they embay. This suggests a material composition link rather than a genesis by regional extensional forces generated by magmatic rises.

The blue areas are where this same science team think an intermittent inland sea once existed. This new data reinforces that hypothesis.

Features that look like mud volcanoes are common in the icy northern lowland plains. Finding them in the dry equatorial regions strengthens the theory that water was once common there. For this reason the scientists are proposing a mission to this location, especially because the possibility of water might increase the chances of discovering past life.

Review of orbital images confirms source of largest Mars quake was not an impact

Location of May quake
The white patches mark the locations on Mars of the largest quakes
detected by InSight. The green dotted patch marks this particular 4.7 quake.

Scientists reviewing images from several different orbiters have confirmed that the source of the largest Mars quake detected by InSight, 4.7 magnitude, was not caused by a meteorite impact and thus proves that movement in the interior of Mars is still occurring.

The quake, which had a magnitude of 4.7 and caused vibrations to reverberate through the planet for at least six hours, was recorded by NASA’s InSight lander on Wednesday 4 May 2022. Because its seismic signal was similar to previous quakes known to be caused by meteoroid impacts, the team believed that this event (dubbed ‘S1222a’) might have been caused by an impact as well, and launched an international search for a fresh crater.

…During its time on Mars, InSight (which was co-designed by the University of Oxford) recorded at least 8 marsquake events caused by meteoroid impacts. The largest two of these formed craters around 150m in diameter. If the S1222a event was formed by an impact, the crater would be expected to be at least 300m in diameter. Each group examined data from their satellites orbiting Mars to look for a new crater, or any other tell-tale signature of an impact (e.g. a dust cloud appearing in the hours after the quake).

After several months of searching, the team announced today that no fresh crater was found.

You can read their paper here. To do the survey, the team used data from the American orbiters Mars Reconnaissance Orbiter and Mars Odyssey, and also enlisted help from scientists controlling the data from Europe’s Mars Express, China’s Tianwen-1, India’s Mangalyaan, and the United Arab Emirates’ Al-Mal.

The results suggest the quake occurred at “a dip-slip fault in the mid-crust, consistent with an origin between 18 and 28 km depth,” as stated in the conclusion of their paper. More analysis is necessary, but this result proves that the Martian interior still active enough to produce relatively large quakes..

More Martian inverted rivers?

More Martian inverted rivers?
Click for original image.

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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Ancient flood lava on the upper slopes of the solar system’s largest volcano

Ancient flood lava
Click for original image.

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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Martian pseudo-frost terrain

Martian pseudo-frost terrain
Click for original image.

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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Massive landslide in Martian canyon

Massive landslide in Martian canyon
Click for original image.

Cool image time! The picture to the right, cropped, reduced, enhanced, and annotated to post here, was taken on September 5, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The image shows a gigantic landslide collapse on the southern interior wall of a long meandering canyon on Mars dubbed Bahram Vallis. The collapse was what scientists call a mass wasting event, in which the entire section of cliff wall breaks off and moves downward as a large unit. In this case the falling section, a half mile wide and long, got squeezed near the bottom, piling up rather than flowing out into the canyon floor.

At this particular location the canyon is 2.4 miles wide, with cliff walls about 1,700 feet high. Imagine when this piece broke off: In one instance a giant section of mountain about a half mile long fell about a thousand feet. Even in Mars’ thin atmosphere the sound must have been thunderous.
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Distorted Martian craters

Overview map

Distorted Martian craters
Click for original image.

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.

Enigmatic terrain amid camera problems on Mars Reconnaissance Orbiter

Enigmatic terrain amid MRO camera problems
Click for original image.

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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Layered ice sheets on Mars?

Overview map

Layered ices sheets on Mars?

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.

Is this the source of the sand for the giant dune sea that surrounds the Martian North Pole?

Overview map

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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A gully in Mars’ glacier country

Overview map

A gully in Mars' glacier country
Click for original image.

Cool image time! The picture to the right, cropped, reduced, sharpened, and brightened to post here, was taken on July 8, 2023 by the high resolution camera on Mars Reconnaisance Orbiter (MRO).

The white dot in the southwest corner of 146-mile-wide Lyot Crater on the overview map above marks the location, smack dab in the middle of the 2,000-mile-long northern mid-latitude strip I dub glacier country, since practically every high resolution picture shows some glacial features. This picture is no different. The material in the upper right of the picture appears to be ice that fills the crater and laps up against its interior slope. The gully appears to suggest a drainage down into that ice that partly covered it.

The elevation change from the high to low points is about 4,500 feet. What drained down this slope to carve this gully however remains an unsolved mystery, though most scientists presently favor some form of water or brine flow in the past and no longer active.

The global wind patterns on Mars, determined by the orientation of dunes

Mars global wind patterns

Wind patterns at the Martina North Pole

Scientists have now roughly determined the global wind patterns on Mars, based on the orientation of one type of crescent-shaped dune called barchan dunes.

The global map above and the north pole map to the right come from figure 2 of the paper. The colored letters indicate the location of additional close-up images. On the polar map Olympia Undae is Mars’ largest dune field. From the abstract:

Crescent-shaped sand dunes are prevalent across the deserts of Mars. Here, we use the physical relationship between the shape of these dunes and the winds that form them to infer the directions of surface winds on Mars on a global scale. We find that dunes typically adhere to the global circulation patterns of Mars’ atmosphere, and that local topographic winds are mostly important in areas with high topographic roughness such as inside deep impact craters. Our global wind map can serve to calibrate numerical climate models, which in turn can help us learn about the recent and modern-day climate of Mars.

The arrows on both maps indicate the direction of the prevailing winds. This data will also help clarify the orientation of many surface features seen by Mars Reconnaissance Orbiter’s high resolution camera. This data also helps explain why the lander InSight never got a burst of wind to clear the dust from its solar panels, while the rovers Spirit and Opportunity did. The rovers were located in regions with clear prevailing winds. InSight was not.

The base of the long and deep south rim of Valles Marineris

Overview map

The base of southern slope of Valles Marineris
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on July 14, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), showing the very bottom section of the long and endlessly deep south slopes of Valles Marineris, the largest known canyon in the solar system.

The many layers here are likely evidence of repeated volcanic flood lava events, over several billion years, after which the canyon formed.

On the overview map above the black dot in the southeast section of the area of the canyon dubbed Melas marks this location. The picture’s northeast corner is essentially the floor of Valles Marineris. From this point the elevation gain to the southwest corner of the picture 3.5 miles away is about 3,300 feet.

The rim itself however is far far higher, about fifty miles farther to the southwest and climbing about 22,000 feet more. Along those fifty miles you’d have to also climb over two intervening mountain ranges, one about 4,000 feet high and the second about 6,000 feet high.

Valles Marineris is big, so big it is hard to imagine a canyon this size. It makes many moutain ranges on Earth seem small.

A mountain buried by lava on Mars

A mountain buried by lava on Mars
Click for original image.

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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Almost all of Mars’ geological mysteries in one spot

Almost all of Mars' geological history in one spot

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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Strange wormlike tube features on slopes of Martian shield volcano

Strange tubes on Mars
Click for original image.

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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A close-up of the giant crack that almost splits Mars

A close-up of the crack that splits Mars
Click for original image.

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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Visible ice layers in a crater in the lower mid-latitudes of Mars?

Visible ice layers in the low-mid-latitudes of Mars?
Click for original image. For the original color image, go here.

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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The northern interior rim of the largest volcano in the solar system

Northern interior rim of Olympus Mons
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 8, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the northernmost interior rim of the caldera of Olympus Mons, the largest volcano in the solar system.

This one picture provides another way to illustrate the monumental scale of much of Mars’ topography. From the top to the bottom this steep scarp descends about 5,900 feet, in a little more than two miles. Compare that to the trails that descend the Grand Canyon’s south rim, which drop about the same distance but do it in distances ranging from three to five times longer.

In other words, this cliff wall is steep. Finding a route for a trail either up or down would be difficult at best.
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A triangular Martian hill

A triangular Martian hill
Click for full image.

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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Polygons and scallops in the high mid-latitudes of the Martian lowland plains

Polygons and scallops in the high mid-latitudes of Mars
Click for original image.

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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The drying out of Mars’ tropics

The drying out of Mars
Click for original image.

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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Ridge in Martian lowland plains

Tiny ridge in Martian lowlands
Click for original image.

Today’s cool image is interesting not because it shows us some spectacular Martian terrain, but because the most distinct feature is a thin ridge only a few feet high that pokes up out of the northern lowland plains for apparently no reason.

The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 1, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The ridge is about 1.8 miles long, and is only about five feet high on its western end, rising to about 25 feet on its eastern end.

The colors differences indicate that the ridge’s peak is likely bedrock, and the surrounding greenish/blue hue suggesting sand and rocks covered with dust. The ridge might be the top of a deeper buried topological feature but that is only a guess.
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Layered glaciers in two small Martian craters

Layered glaciers in two small Martian craters
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on April 7, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what planetary scientists label somewhat vaguely as “layered deposits,” because though the features inside both of these craters strongly resemble glacial ice features, until this is confirmed a good scientist remains skeptical.

I can be more bold, and call the layers glacial in both of these small and very shallow craters (less than a 100 feet deep). To explain this it is important to understand that the lighting and shadows make it hard to distinguish the high points of these layers. Based on the elevation data from MRO, the ground descends to the south, and the mesa in the southern half of each crater’s floor is actually far below the layers and material to the north.

This elevation data suggests that the layered material is surviving best against the crater’s northern interior wall, which at this latitude, about 36 degrees south, will be in shadow the most.
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Martian mounds surrounded by moats

Martian mounds with moats
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on February 1, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the camera team labels “Circular Mounds Surrounded by Moats,” which when all the known data is considered are probably caused by a spray of small meteorites landing on a field of ice.

Why ice? The location is at 37 degrees south latitude, in the cratered southern highlands of Mars, where many images show glacial-type features inside many craters. In fact, all the nearby craters at this location appear to have such features, suggesting the presence of near-surface ice trapped in these craters.

The picture actually looks at the floor of another such crater, with the mounds in the image’s upper left the crater’s indistinct central peaks. Though only 8.5 miles wide, the crater is deep, with interior walls that quickly rise 2,800 feet to the rim. That depth further suggests ice, as any snow that fell here in the far past could easily become trapped, inside what could be thought of a cold trap.
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