Sublimating ice in the Martian dry tropics?

Sublimated ice in the Martian dry tropics?
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on May 3, 2025 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled merely as a “terrain sample,” it was likely snapped not as part of any specific research project but to fill a gap in the camera’s schedule so as to maintain the camera’s proper temperature.

When the MRO camera team does this, they try to pick features of interest at the time required, and I think succeed more often than not. In this case, they captured this one-mile-wide unnamed crater that appears to be filled with sublimating glacial debris. Similarly, the plateau surrounding the crater seems to also show signs that some sublimation is occurring of ice just below the surface, producing the areas that appear filled with pockmarks.

The location however suggests that if near surface ice here is sublimating away, it hints at a find of some significance.
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Scientists: Jezero Crater’s theorized lake overflowed intermittently four times in the past

The inlet and outlet valleys of Jezero Crater
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Scientists analyzing the Martian geology of the meandering outflow canyon from Jezero Crater, now think it was formed by four different very short-lived events when the theorized lake inside the crater overflowed the crater rim.

The map to the right, figure 1 of the paper (cropped and annotated to post here), provides the context. Two canyons, Sava Vallis and Neretva Vallis feed into Jezero Crater, and one canyon, Pliva Vallis, flows out. From the abstract:

By examining the shape of the valley, we noticed that Pliva Vallis was not like valleys carved by continuous rivers on Earth and propose instead that the valley was carved by at least four episodes of lake overflow. To give a minimum estimate of the duration of these events, we use a numerical model to simulate the overflow of a lake and the incision of a valley. Modeling suggests that the four (or more) episodes identified each incised part of the valley and that each episode lasted a few weeks at maximum.

The researchers also considered whether Pliva Vallis could have been carved by glacial flows, but rejected that possibility partly because “the general morphology of the valley shows a decrease in depth and width downstream, while subglacial channels [on Earth] tend to remain of similar width or become larger, as the flow regime does not decrease downstream.”

These conclusions of course carry a great deal of uncertainty. For one, they are based solely on orbital data. No ground truth exists as yet. Secondly, they assume the geology on Mars behaves in the same manner as on Earth. It could very well be for example that the reason the valley shrinks in size is because its Martian glacier sublimated away as flowed downhill, something that doesn’t happen on Earth.

Regardless, the data strongly suggests that water shaped Jezero in some manner.

Scientists: Martian gullies formed by CO2 frost, not water flows

Frost on Martian hillside
Dry ice frost on Martian cliffs. From a 2020 post.
Click for full image.

A new analysis of the gullies found on cliffs on Mars, usually on the interior rims of craters, has concluded that carbon dioxide frost is the cause of the erosion, not ancient flows of water.

This conclusion eliminates the need for liquid flowing water in the Martian past, at least in conjunction with gullies. From the paper’s conclusion:

These results show that CO2 frost is capable of producing Martian gully morphologies. Since flows powered by this process are known to be ongoing and capable of transporting the necessary volume of material, it is the simplest explanation for their formation. Variations in the frequency and fluidity of flows could have occurred over time due to variations in the CO2 cycle. CO2-driven gully formation would indicate that there was not necessarily regular, recurring meltwater during high-obliquity periods. This removes a constraint on recent climate, and also addresses a paradox: if obliquity regularly exceeds the current value as generally thought, and if gullies formed via snow melting at high obliquity, the Late Amazonian Epoch should have included regular snowmelt and widespread aqueous processes. Gully formation by CO2 frost processes is consistent with a cold-desert Late Amazonian with rare or small amounts of liquid water and little aqueous weathering, consistent with the observed mineralogy.

…Gullies, one of the most-discussed lines of evidence for liquid water on Mars, may in fact have no direct connection to H2O. CO2 frost-fluidized gully formation also has broader implications for geomorphology, widening an emerging field of new landform types and processes without Earth analogs. Similar processes could occur on other worlds with erodible substrates on steep slopes and volatile ices at their frost point, although we currently lack the high-resolution images needed to test this hypothesis. Such ices include N2 on Pluto and Triton, and SO2 on Io. [emphasis mine]

In other words, though the gullies appear at first glance to our Earth eyes to have been caused by water flowing downhill, in fact the data now suggests the annual CO2 frost cycle of Mars is the prime cause, even in the distant past. No surface water was required. And since no one has yet come up with a good model for liquid surface water even existing in the Martian past (the atmosphere being too cold and thin), this conclusion helps eliminate this conflict.

The paper also notes the lack of water likely eliminates the need for any planetary protection efforts at these gullies, as the lack of water makes the likelihood of any microbiology nil.

As these conclusions are based on lab work and analysis of images, there remains great uncertainty. Nonetheless, the results help reinforce the arguments that the geological features we see on Mars were formed not by flowing liquid water but by other processes, such as glaciers of ice.

Glacial material even in Mars’ Death Valley

Glacial material even in Mars' Death Valley
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on October 25, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels this a “layered feature,” which is appropriately vague in order to not prematurely push a conclusion that is not yet proven. Extensive orbital imagery and data however strongly suggests the layers inside this crater are glacial in nature, each layer laid down during Mars’ many thousands of climate cycles as the planet’s rotational tilt swung back and forth from 11 degrees to 60 degrees. According to the most popular theory today, when that tilt was high, the mid-latitudes (where this 3,000-foot-wide unnamed crater is located) were actually colder than the planet’s poles. The water ice at the icecaps would then migrate from the poles to the mid-latitudes, causing the glaciers to grow.

When the tilt was low the process would reverse, with the mid-latitudes now warmer than the poles, causing the glaciers to shrink. The wedding cake nature of these layers is likely because, over time, Mars has steadily lost its total budget of water to space, so with each cycle the glacier could not grow as much.

Though many such glacial-filled craters have been found in the mid-latitudes, reinforcing these theories, the location of this crater is even more interesting.
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The weird landscape in Mars’ glacial country

Overview map
Glacier country in the northern mid-latitudes of Mars

The weird landscape in Mars' glacier country

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on November 4, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels the features in the lowland below the mesas “ribbed terrain.” To me it looks like peeling paint. What it is however is glacial material, a lot of it. The white dot on the overview map above marks the location, in the middle of the 2,000-mile-long mid-latitude strip in the northern hemisphere I label glacier country, because practically every high resolution image of this region shows glacial features like those on the right.

The mesa with the crater on top gives a clue on the geological history. This is chaos terrain, a region of random mesas cross-crossed with canyons and wide low plains, as shown in the inset. The entire surface was probably once at the same height as the top of that mesa with the crater. Over time glacial ice eroded away along fault lines. As that sublimation process continued, the fault lines widened to became canyons, then the flat plains, with the isolated mesas remaining between.

The “peeling paint” terrain is likely a layer of ice that is in the process of sublimating away.

Gullies on crater wall

Gullies on Mars
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on August 8, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The picture’s research focus is the gullies, which the scientists’ describe as “perched pole-facing gullies on ancient crater wall.” Perched means the start and end of each gully is on that crater wall, linked neither to the top or bottom of the wall itself. That the gully starts below the top means whatever caused it came from within the wall itself, not from the plateau above. That it ends before the crater floor means the process that cut the gully out was not powerful enough to reach the bottom.

That the gullies are on the interior north wall of this unnamed 25-mile-wide crater means they get less sunlight year round, something that must play a part in causing the gullies.
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Meandering channel inside a larger glacial-filled valley

A meandering channel
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Cool image time! The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken on October 9, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The scientists label this “Channel in North Warrego Valles,” referring to the meandering channel on the left side of the picture. Note the stippled look of the surrounding terrain. This surface appears to be brain terrain, an as-yet unexplained feature on Mars that is always associated with near-surface ice features.

This location is at 40 degrees south latitude, placing it in the mid-latitudes where lots of glacial features are often found on Mars. Thus, it shouldn’t be surprising to find at this location brain terrain, or a meandering channel. The location however is a bit unusual, and reinforces once again that there is a lot of near-surface on Mars, readily available, as long as you are above 30 degrees latitude north or south.
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Ridges from fractures at the head of a 300+mile-long Martian drainage channel

Ridges from fractures on Mars
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on October 4, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels this “Exhumed Fracture Network,” referring to the criss-crossing ridges on the eroded mesa at the picture’s center. That mesa only rises about sixty feet from the east-west channel at the top of the picture, but the location is actually on the outside northern rim of an unnamed 70-mile-wide very eroded ancient crater. The rim itself rises another 500 feet to the south before descending 10,000 feet to the crater floor.

I am assuming by the title that the geologists believe this ridges were originally cracks that got filled with more resistant material, probably lava. The fracture network then got covered over. More recent erosion removed the material around the cracks, but the material in the cracks resisted that erosion.

The most intriguing feature in this picture however might actually be that nondescript channel.
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Graceful beauty found within the mid-latitude glaciers of Mars

Overview map

Graceful beauty found within the glacial mid-latitudes of Mars
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on October 27, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The red dot on the overview map above marks the location, about 35 miles southwest of the rim of 80-mile-wide Moreau Crater. This location is also deep within the 2,000-mile-long northern mid-latitude strip I label glacier country, as almost every high resolution picture from MRO shows glacial features.

This picture is no different, in that it shows the typical lineated parallel grooves seen on the surface of glaciers both on Earth and Mars, and especially found on glaciers flowing within a narrow canyon, as this glacier is. The parallel grooves are caused by the waxing and waning of the glacier. Each layer represents a past period when ice was being deposited on the surface, with the grooves indicates times when that ice was sublimating away. The graceful curves of the grooves is due to the drift of the glacier itself downhill.

This canyon is about seven miles wide at this point, formed from the confluence of two southerly tributaries to the south. The downward grade is to the north, but the low point is not where you would expect, out into the northern lowland plains. Instead, I have marked the low point in the inset with a white dot, inside the canyon itself. It appears this glacier drains into this low spot, but then this debris-covered ice appears to vanish.

It can’t really vanish, but there is a geological mystery here that involves the alien nature of Mars. For some reason the glacier dies at this point, its material sublimating away. Is there a drainage here that sends the ice to the north by underground passages? Your guess is as good as mine.

The lineated nature of this glacial flow however is no mystery in one respect. It is quite beautiful, as seen from space.

Strange mesas in the glacier country of Mars

Overview map

Strange mesas in the glacier country of Mars

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on October 2, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The white dot in the overview map above marks the location, inside the chaos terrain of Deuternilus Mensae and part of the 2,000-mile-long mid-latitude Martian strip I label “glacier country,” because practically every image of every part of its landscape has glacial features. For example, the splash apron around the picture’s largest crater as well as the material within it all suggest some form of glacial activity and near-surface ice.

The scientists label what they see here as “Mesas in Small Craters.” These features are located in a low flat plain that geologists think was created when the ground eroded away, leaving behind scattered high plateaus that indicate the previous surface elevation. The geological map [pdf] of this plain describes it as follows:

Smooth, relatively featureless materials with regions of variable albedo north of continuous cratered highlands; exhibits scattered clusters of small circular to irregular knobs.

Based on the many accumulated photos from MRO, the general conclusion is that we are looking at a sheet of ice/dirt and covered by a thin dust layer that acts to protect that ice from sublimating away. When wind blows that dust off and the summer sun hits that near-surface ice, however, it does sublimate in bursts, which thus provides an explanation for the erosion that caused these low featureless plains.

As for these strange terraced mesas inside these distorted hollows, my guess is that the mesas predate the icesheet and are made of material with less ice impregnated within it. As that ice sublimates away it creates the craters within which the mesas remain. The terraces suggest a earlier series of geological sedimentary history.

Unusual light-colored Martian dunes

Unusual light-colored Martian dunes
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 27, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The picture was simply labeled a “terrain sample,” which usually means it was taken not as part of any specific research request, but to fill a gap in the schedule so as to maintain the camera’s proper temperature. When such gap-filler pictures are necessary, the MRO camera team tries to snap something of interest. Sometimes the pictures end up somewhat boring. This time however the picture highlights a dune field that is unusually light in color.

Since most Martian sand is volcanic in origin, it tends to look dark in orbital pictures. That this sand looks bright could be because it is inherently different, or it could be that lighting conditions make what normally looks dark to look bright instead.
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Distinct gully draining the side of a Martian crater

Distinct gully in crater on Mars
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on August 20, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labels the entire picture simply as “gully,” obviously referring to that distinct and somewhat deep hollow in the middle of the picture.

Most gullies that have been found on Mars tend to look more eroded and rougher than this hollow. Here, it appears almost as if the process that caused this gully occurred relatively recently, resulting in its sharp borders that have not had time to crumble into softer shapes.

The crater interior slope is about 1,500 feet high. Whatever flowed down it however did not do it in an entirely expected manner. As it flowed it curved to the west, so that the impingement into the glacial material that fills the crater floor is to the west of the gully itself. Either that, or that impingement was caused by a different event at a different earlier time.
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Meandering channels on Mars

Meandering channels on Mars
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on August 2, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The scientists describe this as “meandering channels,” which seems appropriate. The downhill grade here is to the southeast. In wider views these channels extend from the northwest to the southeast about 31 miles total (with this location near the center), with the total elevation loss about 3,000 feet.

Note the splash apron around the 4,500-foot-wide unnamed crater as well as how the largest channel seems to terminate suddenly at the crater. Though at first glance it appears this impact occurred after the channels, that some of the channels cut into that splash apron suggests otherwise.
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A different kind of chaos on Mars

A different kind of chaos on Mars
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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, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I had originally chosen to feature a different picture of this spot, taken on August 1, 2024 in order to create a stereo pair, but this week the camera team featured this first photo, providing a caption.

This disrupted surface is characterized by a collection of rounded to flat-topped mounds of various sizes connected by narrow flat floors, typical of the aptly named “chaotic terrain” on Mars.

What could have caused this flat surface to break into pieces? You might imagine that a flat surface could be broken up if it was inflated or collapsed. One hypothesis is that large amounts of water were released from deep below the ground to cause the surface break up.

Normally on Mars, especially in the mid-latitudes, chaotic terrain is associated with glacial activity, suggesting that glaciers over time erode valleys along random criss-crossing fault lines to create the mesas and canyons. This patch of chaotic terrain however suggests a different formation process.
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A puzzling striped rock on Mars

A striped rock on Mars
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 13, 2024 by one of the high resolution cameras on the Mars rover Perseverance. The rock’s striped nature makes it unique, unlike any feature spotted by any rover previously. From an update today:

The science team thinks that this rock has a texture unlike any seen in Jezero Crater before, and perhaps all of Mars. Our knowledge of its chemical composition is limited, but early interpretations are that igneous and/or metamorphic processes could have created its stripes. Since Freya Castle [the name the science team gave the rock] is a loose stone that is clearly different from the underlying bedrock, it has likely arrived here from someplace else, perhaps having rolled downhill from a source higher up. This possibility has us excited, and we hope that as we continue to drive uphill, Perseverance will encounter an outcrop of this new rock type so that more detailed measurements can be acquired.

Without doubt the rock’s rounded surface suggests it was ground smooth by either water or ice. That surface certainly resembles glacial cobble seen across the northeast of the U.S. where ice glaciers once covered the entire landscape. The rock also resembles river cobble, smoothed by flowing water.

The stripes however suggest that prior to its being smoothed, this rock underwent a much more complex geological process, whereby two different materials were intermixed and squeezed together.

Finding beauty on Mars in all the strange places

Overview map

Beauty on Mars
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Cool image time! The picture to the right, cropped to post here, was taken on May 23, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The white dot in the inset of the overview map above indicates the location on Mars, smack dab in the middle of the 2,000-mile-long mid-latitude strip that I call glacier country, because practically every close-up image of this region shows glacial features.

This picture is no exception. The arrows in the inset show the downhill grade, falling about 1,700 feet across the entire inset. That grade is a reflection of the transition that takes place in this glacier country from the cratered southern highlands to the northern lowland plains.

I decided to crop the image at full resolution — showing only a tiny portion — because to my eye these curving linear grooves, produced naturally as Mars’ climate cycles cause glaciers to shrink and then grow repeatedly so that each cycle lays down a new line while squeezing the previous lines, are almost like a work of art. This might be nothing more than a glacier on an alien planet, but nature has caused it to form a very beautiful picture.

Buried peaks in a sea of Martian sand

Buried peaks in a sea of sand
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on April 13, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the MRO science team labels as “streamlined features”, though that doesn’t seem to me to be the best description.

Granted, the prevailing winds, from the northeast to the southwest, appear to pushing the sand dune fields to the southwest. The dark line — created recently by a dust devil — indicates the wind direction. The mesas, from 100 to 200 feet high, do not however appear very streamlined. Instead, they simply look like they are poking up through this sea of sand and dunes, with the wind able over time to successfully push that sand uphill a hundred-plus feet into the saddle between the mesas.

The overview map below provides some context and possibly an explanation, though not a very conclusive one.
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The insane mountain slopes of Mars’ deep canyons

Overview map

The insane mountain slopes of Mars' deep canyons
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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.

A Martian lava flow so strong it eats mountains

A Martian lava flow so strong it eats mountains
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Cool image time! The picture to the right, rotated, cropped, reduced, sharpened, and annotated to post here, was taken on March 19, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a crater that appears to sit on top of a plateau that was created by a flow of material coming from the northeast that — as the flow divided to get around that crater — it wore away the ground to leave the crater sitting high and dry.

What was the material in that flow? The location is at 9 degrees north latitude, in Mars’ dry tropics, so it is highly unlikely that the flows here are glaciers, even though they have some glacier-like features.

Instead, this is frozen lava, but Martian in nature in that its ability to push the ground out of its way suggests it was moving very fast, far faster than lava on Earth.
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Glacial tributaries draining south on Mars

Glacial tributaries draining south on Mars
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on March 27, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as a “valley network”, what appears to be several tributaries flowing downhill from the northeast to come together into a larger single flow to the southwest. The elevation drop from the high to the low points in this picture is about 600 feet.

What formed the valleys? This location is at 35 degrees south latitude, so we are almost certainly looking at what appear to be shallow glaciers within those valleys, protected by a thin veneer of dust and debris. It also appears that the stippled surrounding plains might also contain a lot of near-surface ice, also protected by a thin layer of dust and debris. The stippling indicates some sublimation and erosion.
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Flat tadpole depression in ancient Martian crater

Flat tadpole depression in ancient Martian crater
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Cool image time! The picture to the right, rotated, cropped, reducedl, and enhanced to post here, was taken on February 24, 2024 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 specific research project but to fill a gap in the camera’s schedule so as to maintain that camera’s proper temperature. When they have to do this, they try to pick interesting targets, though there is no guarantee the result will be very interesting.

In this case the camera team already knew this location would have intriguing geology, based on an earlier terrain sample taken a year ago only eight miles to the south. The landscape here is a flat plateaus surrounding flat depressions, some of which appear connected by drainage channels. Today’s picture shows one flat depression with a short tail-like channel flowing into it.

Note the pockmarked surface. The many holes could be impact craters, but they also could be holes caused when the near-surface ice at this location sublimated into gas and bubbled upward to escape. Now all we see is dry bedrock, the flat ground riddled with holes.
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Infeeder to a Martian paleolake

Infeeder to a Martian paleolake
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Cool image time! The picture to the right, rotated, cropped, and reduced to post here, was taken on December 21, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as an “inlet to a paleolake.” I have used this context camera lower resolution image taken January 14, 2023 to fill in the blank central strip caused by a failed filter on the high resolution camera.

The elevation difference between the plateau on the lower left and the lake bottom on the upper right is about 700 feet. The inlet channel floor is about 200 feet below the plateau. We know it is ancient because of the number of small craters within it as well as on the lakebed below. It has been a very long time since any water or ice flowed down this channel to drain into the lake to the north.

While a lot of analysis of orbital data has found numerous examples of paleolakes in the dry equatoral regions of Mars (see here, here, here, here, and here , this particular example is so obvious not much analysis is needed, as shown in the overview map below.
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A Martian rock with holes

A Martian rock with holes
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on April 13, 2024 by the high resolution camera on the Mars rover Perseverance.

The largest rock in the picture is probably only one or a few feet or so across. It has two holes, one very visible in the center and a second less obvious in the shadow on the right. What makes the obvious hole most intriguing is that it appears it was formerly entirely enclosed by the boulder, and was exposed when a section broke off. That section is the smaller rock in the foreground. I wonder if the Perseverance team will bring the rover around to get a view of that smaller rock, to see if it has its own corresponding part of this hole.

Note the smoothness of the rocks. This smoothness is very similar to what Curiosity saw when it was either on the floor of Gale Crater, or at the base of Mount Sharp. In both cases that smoothness suggests either flowing water or glacial ice erosion, like the smooth cobbles one routinely finds in streambeds or in the moraines of glaciers.

As Curiosity climbed Mount Sharp the smoothness was replaced with a delicate flaky fleecework indicating many layers but little violent erosion capable of smoothing the surface (see for example the images here and here). It appears Perseverance is still low enough in Jezero Crater to be within the ancient active region, formed from flowing water or ice.

As for the holes, my guess is that this rock formed from lava, and the holes are what geologists call “vugs”, bubbles formed within the lava as it solidified.

Bursting bubbles of water gas on Mars

Bursting bubbles on Mars
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Cool image time! The picture to the right, cropped, reduced, and enhanced to post here, was taken on January 12, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Because of a technical issue that leaves a blank strip down the center of recent high-res MRO images, I have filled in that gap using a MRO context camera photo taken on January 12, 2015. The resolution is much less, but by doing so we can see the ground features as a unit.

What are we looking at? According to the scientists, this picture shows “fresh-looking ruptures,” referring to the broken line of sharp tears inside that meandering canyon that almost resemble a fresh wound in flesh. As this location is at 28 degrees south latitude, it lies on the edge of dry equatorial regions, where orbital images have sometimes found hints of a few remaining buried glaciers that are much more common closer to the poles.

In this case it appears the warmer equatorial climate has acted to heat up the buried ice so that it sublimated into gas. At some point the gas pressure caused the surface to burst, much like bubbles bursting on the surface of a pot of simmering tomato sauce, leaving behind these scars.
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Some more “What the heck?” geology on Mars

What the heck?
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on January 1, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small part of a region dubbed Iani Chaos, but what this geology shows is way beyond my pay grade.

Why there are those tiny aligned mounds, oriented at right angles to the slope, is not clear at all. Nor is it obvious what created the lighter chaotic terrain at the base of the slope.

The elevation difference between the low and high points is about 400 feet. The slope continues up to the west for another 600 feet to the top of a north-south ridgeline. The patterns here suggest vaguely some flows downhill, such as that widening east-to-west gap, but only vaguely.

The look at the overview map only compounds the mystery.
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A Martian tadpole

Overview map

A Martian tadpole
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 28, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The white dot on the overview map above marks the location, with the rectangle in the inset marking the area covered by the picture. The science team labels this “inverted features,” a more vague way to describe the feature geologists dub “inverted channels.” The flow of a river or glacier acts to harden and increase the density of the channel bed. Later, the water or ice disappears, leaving just the canyon.

Even later, erosion begins to wear away the surrounding terrain. Because the canyon floor is now harder than that surrounding terrain, that floor is more resistent to erosion, and eventually becomes ridge following the exact same path as the long gone river or glacier.

This is what we have here, with this inverted channel, which is about five miles long, once draining into the deeper eroded valley to the south.

The location is at 38 degrees north latitude and inside the 2,000-mile-long mid-latitude region I dub glacier country, because almost every image shows evidence of glaciers or ice flows on the surface. This picture however is a rare exception. The features in this picture instead appear to be bedrock, something that is rarely seen in the canyons and craters in glacier country. It is beyond my pay grade however to explain why this spot lacks such features. Or it could be the near surface ice here looks so much like bedrock I am misinterpreting the picture.

Another helicopter mission under development for Mars?

Another helicopter mission for Mars?
Click for original image.

Today’s cool image to the right, cropped to post here, is probably on its own one of the more boring cool images I have posted over the years, a generally featureless plain with some ripple dunes within a few low hollows.

What makes this picture cool however is the label for the image: “Sample Landing and Traverse Hazards at Possible Helicopter Landing Site.” The picture was taken on January 23, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), with the obvious goal of seeing whether this location can serve as a landing site for a helicopter mission to Mars.

The site is relatively uninteresting because the first goal is to find a safe place to land, but to do so near a location where there is rough geology which only a helicopter can explore. And it appears, from the overview map below, that is exactly what this location is.
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A sunflower crater on Mars

Overview map

A sunflower crater on Mars
Click for original image.

Cool image time! The picture to the right, cropped and reduced to post here, was taken on December 17, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labels a “pedestal crater,” a crater that, because the impact smashed the ground to make it more resistent, when the surrounding terrain eroded away it left the crater sitting high and dry.

In this case the crater is only a few feet higher than that surrounding terrain. In fact, though it looks much deeper than the crater to the northeast, both are so shallow that their depth is below the resolution of MRO’s elevation data.

Both craters however suggest the presence of a lot of near surface ice, which is confirmed by overview map above. The rectangle marks the location, inside the 2,000-mile-long northern mid-latitude strip I dub glacier country, as almost every high resolution picture suggests glacial features and near-surface ice. The crater to the northeast appears filled with glacier debris, while the sunflower-shaped apron around the pedestal crater suggests the impact hit soft ice that splashed away and then hardened.

Though this pedestal crater does not appear to sit high above the plain, the rough edges of its apron illustrate the subsequent erosion. The impact likely stripped away the dust/debris layer that protected the glacial and near-surface ice of that splash apron so that sunlight would cause it to sublimate away. Thus we have that knobby surface at the edges.

Martian gullies caused by glacial and water erosion

A gully on the north rim of Niquero Crater
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 23, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The image shows us the north interior rim of 7-mile-wide Niquero Crater on Mars. From the high to the low points the elevation difference is about 2,500 feet, with a steep downhill slope averaging about 18 degrees. The terrain appears to show several avalanche collapses that pushed lower material out of the way, though at the bottom where that material has been pushed aside there is no obvious large debris pile.

The science team labels this image simply “volatiles and gullies”, a label that carries a host of significant information. These gullies, which were among the earliest found by Mars Global Surveyor in the late 1990s, were the first evidence that the surface of Mars had a lot of near surface ice. It is for this reason that this relatively small crater on Mars has a name. Most craters this small remain unnamed, but the gullies on Niquero’s north slopes required more study, and thus the crater was given a name.

Subsequent orbital imagery has now shown that craters like Niquero, located in latitudes higher than 30 degrees, quite often are filled with glacial debris. In fact, the material that these avalanches pushed aside at the base of the slope is that glacial material, protected by a thin layer of dust and debris. The avalanche essentially disturbed that protected layer, and thus the debris pile (made up mostly of ice) sublimated away when warmed by sunlight. Thus. no big debris pile.

The gullies tend to be on the pole-facing slopes. Scientists believe they are the remnant evidence of ancient glaciers that grew on these slopes because they were protected from sunlight. In subsequent eons, when the climate on Mars changed, those glaciers collapsed, leaving behind the gullies we see now.
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A small Martian volcano?

A small Martian volcano?
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on December 21, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labeled it a “fresh crater”, but that description I think is misleading, as it implies a recent impact.

The crater does not look like a fresh impact crater to me. Such things on Mars usually appear very dark, as the impact dredges up dark material. This crater is not dark. More significant is the crater itself. The small 300-foot-wide inner crater, surrounded by a circular plateau and all sitting inside the larger 1,200-foot-wide crater is completely unique compared to any impact crater I have ever seen. Impacts in soft material, such as ice-impregnated ground, can cause concentric ripple rings, but they don’t look like this.

Instead, this crater more resembles the caldera of a volcano, where subsequent eruptions can produce overlapping depressions at the volcano peak. (See for example this picture of Olympus Mons.)

Moreover, the crater sits on top of a peak approximately 300 feet high. While impacts in ice-impregnated ground on Mars can produce splash aprons as seen here, the crater usually sits at about the same elevation as the surrounding terrain, not at the top of a peak. This peak suggests the apron was forned not by a splash but repeated flows coming down from the top.
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