Tag Archives: MRO

Tadpole on Mars

Tadpole on Mars
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Cool image time! The image on the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 7, 2019, and shows a crater on the northern fringe of Arabia Terra, one of the largest transitional regions between the Martian northern lowlands and the southern highlands. It shows a crater with an inlet canyon that makes the entire crater resemble a wiggling tadpole.

This is certainly not first tadpole-resembling crater found on Mars. See for example this press release from February 2018, showing a tadpole crater with the tail being an outlet channel. In today’s image however the channel feeds the crater.

In fact, take a look at the full image. This crater apparently occurred right at the edge of a large mesa cliff, with this impact cutting into the cliff near its bottom. The canyon might have actually existed before the impact, with the crater merely obliterating the canyon’s outlet.

If you look along that escarpment to the east you can see similar southwest-to-northeast flows. One is a canyon flowing downhill through the escarpment, probably resembling what the first canyon might have once looked like before the impact. To the east of this is another tadpole crater. This second tadpole impact however took place on top of the mesa, so the channel flows out from the crater and then down off the mesa, the reverse of the tadpole crater above.

These flow features are consistent with the nature of this transitional zone, a region with many features suggesting it was once the shoreline of an intermittent ocean. That ocean, if it had existed, is long gone, though scattered across the Martian surface are geological ghost features like these that speak of its past existence.


Martian dry ice frost on glacial remains?

Frost on ridgelines and inside crater
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Close-up of frost

Cool image time! The photo on the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on November 30, 2019. Located just east of Hellas Basin in southern mid-latitudes, the color strip shows dry ice frost both in the crater as well as on the ridgelines to the north. As noted in the caption, written by Candy Hansen of the Planetary Science Institute in Tucson, Arizona,

When we acquired this image, it was [winter in the southern hemisphere] on Mars, but signs of spring are already starting to appear at latitudes not far from the equator. This image of Penticton Crater, taken at latitude 38 degrees south, shows streamers of seasonal carbon dioxide ice (dry ice) only remaining in places in the terrain that are still partially in the shade.

The turquoise-colored frost (enhanced color) is protected from the sun in shadowed dips in the ground while the sunlit surface nearby is already frost-free.

Note for example how the frost disappears in the southern half of the crater floor, the part exposed to sunlight.

What immediately struck me however were the underlying features. The entire northeast quadrant of the crater’s rim appears to have been breached by some sort of catastrophic flow, as if there had been a glacial lake inside the crater that at some point smashed through suddenly, wiping that part of the rim out as it ripped its way through.

To the right is a full resolution inset, indicated by the white box above, of the dry ice frost on the outside of the crater. I find myself however drawn more to the underlying features, which once again have a chaotic aspect suggesting a sudden violent event, coming from the south and moving north.

I have no idea if my visceral conclusions here have any validity. At this latitude, 38 degrees, scientists have found a lot of buried inactive glaciers of ice, so I could be right. Or not. Your guess is as good as mine.


Gully on Mars

Gully in crater on Mars
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Cool image time! If we were told that the photo on the right was taken by an airplane over some southwest desert gully, no one should be surprised if we were to accept that description entirely. The gully sure looks like a lot of drainages one can routinely see when flying over the American southwest, dry, treeless, but showing the typical dendritic pattern seen for most desert water drainages.

Of course my readers all know that this is not in the American southwest, but on Mars, in a crater located in the transition zone between the southern highlands and the northern lowland plains. The image, cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on October 12, 2019.

It appears that this particular gully has been subject to repeated monitoring, since November 2015. A rough and very quick comparison of the earlier image with today’s image does not show any obvious change. This does not mean there hasn’t been any evolution, as my look was cursory, and I could easily be missing changes. Seasonal variations might also be occurring that I could be missing.

The reasons for the monitoring are of course obvious. This gully strongly suggests the flow of liquid downhill. Is that occurring today, or are we seeing the evidence of a past flow from long ago? Only some long term monitoring can tell.

There is also the possibility that we are looking at a buried glacier. The crater is located at 42 degrees north latitude, well within that mid-latitude band where scientists have located many buried Martian glaciers. If so, then the monitoring is to see if that glacier is active in any way.


Pedestal craters in the Martian northern lowlands?

Pedestal craters on Mars?
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Cool image time! The photo on the right, cropped and reduced to post here, shows a cluster of really strange mesas, craters, and pits, located in Utopia Planitia, the largest and deepest plain of Mars’ northern lowlands where an intermittent ocean might have once existed.

The image was taken on October 26, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) as part of its regular image-taking program. In this case it was dubbed a “terrain sample” image, meaning that it was not specifically requested by any researcher, but was taken because they need to use the camera regularly to maintain its temperature, and thus sometime produce images over previously untouched areas, not knowing what they will find, as part of that maintenance schedule.

In this case the terrain sampled is especially intriguing. Are the upraised depressions what are called pedestal craters, created when the impact landed on what was once an icy plain, which subsequently sublimated away to leave the crater sitting high above the surrounding flats? Maybe, but this location is at 23 degrees north latitude, and research has generally found these pedestal craters at latitudes higher than 30 degrees.

Moreover, that many of these upraised depressions are not circular suggests that their formation was not impact related.

Other mysteries: Why are all the ridgelines bright? What caused the parallel white streaks to the east and west of some mesas? And if these are impact craters, why are some distorted?

If this region was once the seabed of an intermittent ocean, this fact might explain the features. Then again, it is more likely that this lowland area was once covered in ice in the far past, when the planet’s tilt was greater and the lower latitudes were actually colder than the polar regions, and thus allowed ice to build up in those lower latitudes. We might therefore be seeing the end result of an erosion/sublimation process as that ice disappeared when Mars’ inclination shifted.

Lots of questions, and no answers.


Darkened craters on Mars

Darkened craters on Elysium Planitia
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It’s time for the first cool image of 2020! The photo to the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 10, 2019. It shows a handful of darkened craters on the vast volcanic Elysium Planitia plain between the giant volcanoes Olympus Mons to the east and Elysium Mons to the north.

My first thought was that these dark craters were recent crater impacts, possibly a set of secondary impacts from a larger nearby impact. However, in looking at the archive of MRO’s high resolution camera at this location (Latitude 5.925° norther; Longitude 164.965°) I found that almost no high resolution images have been taken in this region, as shown by the overview map below to the right.
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Giant scallops on Mars

Scallops on Mars
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It’s a slow news week, with the too much partying only real space news today the expected third launch of China’s Long March 5 rocket (supposedly scheduled for this morning but so far no word). (To my gentle reader: For some reason I have been losing a day during this whole week, always thinking that Christmas was on Thursday and that today was Friday. Thus my error in thinking the Long March 5 flight was today. It is tomorrow morning. Forgive me for my absent-mindedness.) So let’s look at a cool image!

The photo on the right, cropped and reduced to post here, was taken my the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 8, 2019. Entitled “Scalloped Depressions in Utopia Planitia,” it shows a strangely eroded surface in the northern lowlands of Mars, where an intermittent ocean might have once existed.

The location of these scallops is shown to the right.

Location of scallops in Utopia Planitia

I have taken the same overview map used from two recent cool image posts, showing how these scallops relate in location to the strange crater in Utopia Planitia as well as the glacial-surrounded mesa in Protonilus Mensae.

In caves, scallops like this form from water or wind flow, but when they do, they are all oriented the same way. Here the scallops are at different orientations, terracing down from the center of the image. In this case it appears that scientists believe [pdf] the formation process is related to the sublimation of underground ice at this location.

According to [one hypothesis] scallop formation should be ongoing at the present time. Sublimation of interstitial ice could induce a collapse of material, initially as a small pit, then growing southward because of greater solar heating on the southern side. Nearby scallops would coalesce together as can be seen to have occurred.

What is most cool is that the geologists think the process that forms these scallops is related to the same processes that cause the formation of the swiss cheese landforms in the south polar regions.


Crater in the Martian northern lowlands

Crater in Utopia Planitia
Click for original full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 26, 2019. It shows a crater in the western edge of Utopia Planitia, the largest and deepest region of the Martian northern lowlands where it is theorized that an intermittent ocean might have once existed.

My first uneducated guess at looking at this image is that the impact occurred in some sort of wet slushy mud or ice, which then melted and filled the crater interior, ponding in the crater’s center as it froze.

A more educated guess, based on what I have learned in the past year, is not much different. The crater is located at 40 degrees north latitude and therefore sits in the middle of the mid-latitude band where scientists think there are a lot of buried inactive glaciers.

Overview map

The map to the right, revised from my December 20, 2019 post about glaciers flowing off the slopes of a mid-latitude mesa, illustrates this even more clearly.

This crater, indicated by the white cross, sits at approximately the same latitude as that mesa and its glaciers in Protonilus Mensae. It also sits at in an area where accumulated data from several spacecraft have mapped a lot of water ice, close to the surface.

Thus, it is reasonable to suppose that the impact that made this crater pushed into that ice-table, melting the water which subsequently froze and then subsided downward into the ground to form the crater’s central ponded features.

Or to put it as I did initially, the impact smashed into some wet slushy mud/ice, melting it so that it filled the crater interior to then freeze as we see it.


A deep dive into Valles Marineris

Dunes on the floor of Valles Marineris
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The vastness of Mars is sometimes hard to fathom. While the planet is much smaller than Earth, its entire global surface is approximately the same as the Earth’s land area. This is a lot of territory. It took humanity many tens of thousands of centuries to expand outward to settle all of it. It took even longer before humanity was successfully able to map all of the Earth so that its entire surface was known to all humans, a task that was only completed a handful of centuries ago.

While we now have the technology to quickly map the entire globe of a planet like Mars, the devil is always in the details. At this time the resolution of our global maps give us only a glimpse of the Martian surface.

The image to the right, reduced and cropped to post here, is a good example. Taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 30, 2019, it shows a set of large dunes on the northern floor of a side canyon on Mars that is part of Coprates Chasma, a canyon that forms only a small part of the vast Valles Marineris canyon system east of the giant volcanoes of the Tharsis Bulge.

The sand of these dunes is mostly volcanic material, dark basalt that was deposited as lava from those giant volcanoes, then later ground down in landslides and erosion to be recycled as sand that formed dunes trapped within the canyon bottom. The dunes themselves are slowly moving eastward, driven mostly by the predominate west-to-east winds that blow down this side canyon of Coprates Chasma. The motion is very slow, so slow that even though the image title is “Coprates Chasma Dune Changes”, I was unable to spot any changes when I compared this 2019 image with a photo taken in June 2019.

To find out what had changed, I contacted Matt Chojnacki of the Lunar and Planetary Laboratory at the University of Arizona, who has been studying the nature of the sand dunes in Valles Marineris. After making a quick preliminary blink test using more sophisticate tools than I have available, he found “minor advancements. The rocks move a bit too in places.” Without a full analysis he also added, “I can tell some dune crests have moved to the east.”

The research by Chojnacki and others has found that the dunes within Valles Marineris are in many ways different than dunes found elsewhere in the mid-latitudes on Mars, suggesting that being trapped within this giant canyon has produced some specific regional features. They tend to be darker, the canyon contains several sand dune seas, called ergs (only seen elsewhere on Mars in the polar regions), and the dunes tend to be more hardened, so that they change relatively little when compared to similar dunes elsewhere on Mars.

These particular dunes in Coprates Chasma however are not hardened, since if so they would have been covered by the landslides and material that comes down from the canyon’s nearby northern slopes. Instead, they move, but appear to move far slower than similar dunes elsewhere on Mars.

To me, this image provides a good vehicle for getting a sense of the size of Valles Marineris. Coprates Chasma itself only one of about a dozen named sections of the entire Valles Marineris canyon system, and this particular image shows only the floor of a side canyon of Coprates. The map below gives an overview of the entire system.
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Buried glaciers flowing off of Martian mesa

Glacial flow off of mesa
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Cool image time! Planetary geologists now think that the mid-latitudes of Mars contain many buried and inactive glaciers, formed several million years ago when the planet’s inclination was more than 50 degrees [pdf], rather than the 25 degrees it is now. At that time the mid-latitudes were actually colder than the poles, and water would sublimate from the poles to the colder mid-latitudes to pile up as snow and glaciers.

With today’s 25 degree inclination those mid-latitude glaciers are inactive, and have been so for several million years. It might even be that Mars’ water is beginning a shift back to the poles, but this is uncertain. If anything the planet is presently in a balance, and won’t start transferring water back to the poles until its inclination drops closer to zero.

The image to the right, taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on September 23, 2019, is of one of those glacial flows, coming off a mesa in a region called Protonilus Mensae, located in the transition zone between the southern highlands and the northern lowland plains where an intermittent ocean might have once existed.

Much of the geology of Protonilus Mensae is chaos terrain, places where the surface has eroded along angled fissures to form many mesas. The overview map below focuses in on the particular mesa where this flow is located. The red boxes indicate all the MRO images taken of this mesa, with the image above indicated by the black dot.
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Megadunes in the giant canyon of Mars’ north polar icecap

Martian megadunes at the beginning of summer
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Cool image time! The photo to the right, cropped and reduced to post here, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on September 15, 2019, right at the beginning of summer at the north polar icecap of Mars.

Without a larger context it is very difficult to figure out what this image shows. The image title, “Seasonal Changes of Chasma Boreale Megadunes,” gives us some basic clues. The streaks of black and dark grey are giant dunes, with this image showing their trailing edge. The darkest streaks are likely places where the thin winter mantle of dry ice has begun to sublimate away with the coming of spring, exposing the darker sand dunes below. The surrounding flat white areas are either the permanent water ice of the icecap or the surface of the lowland northern plains that surround that icecap.

The montage below shows a series of monitoring photos, beginning in 2018 during the last Martian summer and continuing through the start and middle of the spring and ending with the photo above. It shows the seasonal evolution of that upper carbon dioxide dry ice mantle, which reveals the darker dunes below as that dry ice mantle sublimates away.
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Martian impacts and streaks

Slope-streaked crater on Mars
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In the most recent image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO), there was the cool image to the right, reduced and cropped to post here, of a crater that appeared to have hundreds and hundreds of slope streaks along its inner slopes.

Slope streaks are quite mysterious. They are found in the equatorial regions as dark (though sometimes light) streaks on steep slopes, appearing throughout the year and slowly fading over time. They also appear to be a geological phenomenon unique to Mars. Nothing on Earth or any other planet appears to correspond.

As such, their nature and cause remains unknown, though there are a bunch of theories, with the most popular being that these are a kind of dust avalanche. They are always found in connection with dust-covered terrain, but they also make no significant topological change to the surface, other than brightness.

The slope streaks in this crater are especially intriguing, because of the number of streaks. In digging further into the MRO archive I found a number of images of this crater and its surrounding terrain. It appears that sometime before 2012 there was a relatively recent impact close to the exterior of the eastern rim of this crater. The image below, taken in 2014 by MRO, shows this impact as the large dark splotch, with the new crater indicated by the arrow..
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The dark splotches on Mars: Magnets for dust devils

Olympus Maculae, land of dark splotches

One of the numerous geological mysteries that planetary scientists have discovered among the many high resolution images taken by the various Martian orbiters are a series of dark splotches, ranging in diameter from one to fifteen miles, running in an east-west line on the lower western slopes of the giant volcano Olympus Mons.

Scientists have dubbed this string of splotches Olympus Maculae and, because of their superficial resemblance to the islands of Hawaii, have labeled each splotch, or macula, after those islands, as shown in the overview map above, created by geologist Kirby Runyon of the Applied Physics Lab in Maryland as part of a presentation [pdf] given at a science conference in September 2019.

Prior to the 2018 global dust storm on Mars scientists were not quite sure what caused these dark patches. The data suggested the maculae were less dusty than the surrounding terrain, but why this was so was not clear.

The advent of that storm however gave them a chance to get before and after photos. In October 2018 I found several images in monthly download of new images from the high resolution camera of Mars Reconnaissance Orbiter (MRO) and posted them, making a vain attempt to locate what had changed. As I wrote,

I found that MRO has taken images of this location twice before, in 2007 and in 2009. I spent about fifteen minutes trying to find something that had changed, but was unable to locate anything, other than what look like a few wind-blown streaks probably caused by dust devils. I suspect I do not know what to look for.

I then made some guesses about what caused these splotches, all wrong I have since learned.

Since then more images of these splotches have been downloaded from MRO, all once again indicating that changes have been detected. Below is a sequence of images of the splotch dubbed Ka’ula, the first taken in 2008, the second in 2018 just after the global dust storm, and the third in 2019, one year after the storm. Set side-by-side the changes are more obvious.
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A crack in the Martian crust

Crack in the Martian crust
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Cerberus Fossae

The photograph to the right, reduced and cropped to post here, was imaged on October 20, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a spectacular thousand-foot-deep canyon in the region of Cerberus Fossae, an area of Mars crossed by numerous deep east-west fissures and depressions.

Hidden in the small white box on the eastern end of that canyon are Martian geological features, small and at first glance not that interesting, that are of great significance and the focus of intense research.

The map to the right shows an overview of the region. The yellow cross shows the location of this particular crack.

In my previous post about Cerberus Fossae, I had incorrectly assumed that these cracks and similar lines of pits or depressions were caused by the sinking of surface material into underground lava tubes. While this is possible in some cases, it is not the main cause of these cracks. Instead, they were formed due to the pressure from below caused by the rise of the surrounding giant volcanoes, Elysium Mons to the north and Olympus Mons to the east. That pressure stretched the crust until it cracked in numerous places. In Cerberus Fossae this produced a series of parallel east-west fissures, some more than seven hundred miles long.

The young age of Cerberus Fossae is dramatically illustrated by the wider mosaic below, showing the entire crack.
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Martian “What the heck?” formations

What the heck caused these?
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Cool image time! In digging through the new images that come down from the high resolution camera on Mars Reconnaissance Orbiter (MRO), my reaction sometimes is “What the heck caused that?”

That was my reaction when I looked at the image to the right, cropped to post here.

The full image, taken on October 6, 2019, shows the floor of one of the many north-south fissures found in the volcanic Tharsis Bulge west of Valles Marineris and east of Olympus Mons. The fissures are caused when the crust is pushed upward by volcanic pressure, causing the surface to crack.

In this case the mystery is that patch of east-west ridges at the bottom of this somewhat wide fissure. While they might be dunes, they do not resemble dunes, as they have a rigid and somewhat sharp appearance. More puzzling is their somewhat abrupt appearance and disappearance. Except for its northern end, the edges of the patch are so sharply defined. If these were dunes you’d think they’d fade away more gradually.

Could the ridges be a more resistant subsurface feature slowly being revealed as surface material erodes away? Sure, but their orientation is completely opposite to the north-south fissures that dominate this region. One would expect deeper features to reflect that same general orientation. These ridges do not.

This image was dubbed a “Terrain Sample,” which means it was taken not because of any specific research goal, but because the scientists who run MRO’s high resolution camera had a gap in their schedule and needed to take a picture to maintain the camera’s proper temperature. In such cases they often take somewhat random images, not knowing what they will find. In this case they struck geological gold, a mystery that some postdoc student could spend a lot of time analyzing.


More Martian pits, filled and unfilled!

Pit in Ceraunius Fossae
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Overview of Ceraunius Fossae

Time for what has almost become a monthly pit report from Mars Reconnaissance Orbiter (MRO). The November image download from the spacecraft’s high resolution camera included two pit-related photographs, both very different. To the right is the first, cropped to focus on the pit and the immediate surrounding terrain. Below that is a wider overview map to provide the context.

This pit’s location is indicated by the white box at the southern end of a region dubbed Ceraunius Fossae, made of hundreds and hundreds of parallel north-south fissures extending more than seven hundred miles south of the giant volcano Alba Mons and caused when the ground was stretched from below, causing it to crack.

This surrounding terrain helps to explain the pit’s origin. First it is located in a north-south depression with a number of other less pronounced depressions. While these do not line up precisely, they still suggest that they are sinkholes where the surface material is draining downward into voids below. Normally the assumption would be the existence of a lava tube, but here the downward grade is very small. Instead, what is likely happening is that the ground is being stretched, causing cracks to form into which surface material slips downward.

The Ceraunius Fossae fractures are extensional features produced when the crust is stretched apart…. Mechanical studies indicate that a regional pattern of radiating graben and rifts is consistent with stresses caused by loading of the lithosphere by the enormous weight of the Tharsis bulge….Several generations of grabens with slightly different orientations are present in Ceraunius Fossae, indicating that stress fields have changed somewhat over time.

In addition to producing normal faults and graben, extensional stresses can produce dilatant fractures or tension cracks that can open up subsurface voids. When surface material slides into the void, a pit crater may form. Pit craters are distinguishable from impact craters in lacking raised rims and surrounding ejecta blankets. On Mars, individual pit craters can coalesce to form crater chains (catenae) or troughs with scalloped edges.

That’s what we see here. The pit is suggestive of a void below, but it is likely not going to be a long coherent underground passage but a serious of random gaps, aligned roughly along the larger crack and producing the various depressions on the surface.

Today’s second pit is of an entire different nature.
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Mid-latitude Martian glacier?

Glacier on Mars?
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Cool image time! I have posted a lot of Mars photographs in the past few months showing possible glaciers in the mid-latitudes of Mars, where scientists think they have identified a lot of such features. Today is another, but unlike many of the previous examples, this particular feature more closely resembles a typical Earth glacier than almost any I have so far posted.

Based on the image’s title, “Lineated Valley Fill in Northern Mid-Latitudes,” given by the science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO), I suspect that it remains unproven that these are features of buried glacial ice. Thus, they use a more vague descriptive term, lineated, to avoid pre-judging what these features are.

Nonetheless, a glacier is sure what this lineated valley fill looks like. See for example the Concordia confluence of two glaciers in the Karakoram Mountains of Pakistan, near the world’s second highest mountain, K2. Though obviously not the same, you can see many similarities between this Martian feature and Concordia.

MRO has taken only three photographs of this particular valley, with one image useless because it was taken during a dust storm. Yet, the other good image, farther downstream in this valley, shows very similar features.

The valley itself is formed from chaos terrain, located in the transition zone between the southern cratered highlands and the flat northern lowlands where a possible intermittent ocean might have once existed. Thus, for buried ice to be here is quite possible.


Unearthly pit in Martian northern icecap

Giant pit in Martian North polar icecap
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Cool image time! It is spring in the Martian north, and thus the Sun has risen and remains in the sky for most if not all of each day, circling the horizon. As such, it illuminates polar icecap features that are strange and weird and hard to decipher based on our expectations here on Earth.

The photograph to the right, cropped and reduced to post here, is a good example. It was taken on September 20, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows a pit in the outer regions of the polar icecap, an area where that water icecap remains relatively stable, but that is also at a low enough latitude that summer sunlight can cause some erosion and sublimation of the ice.

The bottom of the pit is the center of the bullseye, with the layered features in the surrounding walls showing the many layers inside the icecap, built up over centuries, then slowly revealed as the ice in this pit slowly sublimated away.

You can get a better sense of what you are looking at by the overview map below.
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Sinkholes galore!

Sinkholes galore south of Olympus Mons
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Cool image time! The photograph to the left, cropped to post here, was part of the November image dump from the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a wind-swept dusty plain trending downhill to the west that is filled with more than a hundred depressions or sinkholes.

Unlike other pit images I have posted previously, this one is not focused on one particular pit or a string of pits. Instead, what makes it interesting is the large number of pits, scattered across the terrain in a random pattern. Their random distribution suggests that they are unrelated to any specific underground feature, such as a lava tube. Instead, some aspect of the underground geology here is causing the ground to sink at random points.

Below is an overview map showing where this dusty pit-strewn plain is located, indicated by the blue cross.
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Recent impact on Mars

Recent impact on Mars
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Cool image time! While finding recent impacts on Mars is not that unusual, the image to the right, found among the November image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO), was dramatic enough that I decided that more people besides planetary scientists should see it. For scale the photograph is exactly 500 meters wide.

The photograph, taken September 26, 2019, also illustrates all the typical aspects of impact craters, and how they change the landscape.

This impact took place sometime between July 17, 2012 and January 4, 2018. We know this because it wasn’t there in a low-resolution image taken by the wide angle survey camera on MRO on the first date but was there when that same camera took another picture on the second date. Below is a side-by-side comparison of that July 17, 2012 image with the high resolution 2019 image above.
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A journey into the depths of Valles Marineris

Valles Marineris

Cool image time! Rather than start with the cool image, let’s begin with the long view. To the right is a wide mosaic of Valles Marineris on Mars, the largest known canyon in the solar system. About 2,500 miles long and 400 miles wide, this canyon is so large that it would cover most of the United States if put on Earth. The Grand Canyon, 500 miles long by 19 miles wide, could easily fit within it and not be noticed. In depth Valles Marineris is equally impressive, with a depth of more than four miles, about four times deeper than the Grand Canyon.

A closer view of the central regions of Valles Marineris

The white cross in the mosaic above is where we are heading. You can see it as the white box in the zoomed in overview to the right. This central part of Valles Marineris is named East Melas Chasma, and the red boxes indicate locations where the high resolution camera of Mars Reconnaissance Orbiter (MRO) has already taken images.

As you can see, we do not yet have many high resolution images of this part of the canyon floor. The white box is the most recent image, and is the subject of today’s post.
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Polygons on Mars

Scallops and polygons on Mars
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Cool image time! The photograph on the right, cropped to post here, was taken on September 25, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and made public in its November image release. It shows the weird but very typical scalloped terrain, with its adjacent polygon pattern of fractures, found routinely in the northern lowland plains of Utopia Planitia on Mars. From an earlier captioned image from 2006 of these same features:

The scalloped depressions are typical features; a smooth layered terrain located between 40 and 60 degrees in both hemispheres. Scalloped depressions probably form by removal of ice-rich subsurface material by sublimation (ice transforming directly from a solid to a gaseous state), a process that may still be active today. Isolated scalloped depressions generally have a steep pole-facing scarp and a gentler equator-facing slope. This asymmetry is interpreted as being the result of difference in solar heating. Scalloped depressions may coalesce, leading to the formation of large areas of pitted terrain.

The polygonal pattern of fractures resembles permafrost polygons that form in terrestrial polar and high alpine regions by seasonal-to-annual contraction of the permafrost (permanently frozen ground). On Earth, such polygons indicate the presence of ground ice.

On Earth these polygons are most often seen in mud, usually suggesting a drying process where the ground contracts with the lose of fluid. On Mars the cracks probably also form from contraction, but not by the lose of fluid but the lose of water ice as it sublimates into a gas.

These polygons and scallops illustrate an important feature of Mars’ vast northern plains. On large scales these plains appear flat and featureless. Up close however many many strange features, like the polygons and scallops in this image, come into view.
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Mars’ seasonally vanishing carbon dioxide polar cap

Buzzell dunes, March 19, 2019
Click for full image.

Since the onset of the Martian spring in the northern hemisphere back in March of this year, scientists have been busy using the high resolution camera on Mars Reconnaissance Orbiter (MRO) to monitor the expected sublimation and disappearance of the cap of dry ice that falls as snow to become a winter layer mantling both the more permanent icecap of water 7,000 feet deep as well as the giant dune sand seas that surround that northern icecap.

The image on the right was first posted here on Behind the Black on June 6, 2019 as part of a long article describing that northern polar icecap and its annual evolution. It shows a set of dunes that Candice Hansen of the Planetary Science Institute in Arizona, who requested the image, has dubbed “Buzzell.” When that picture was taken in March, the frozen dry ice layer of translucent carbon dioxide still coated the dunes. The image’s darkness is because the Sun has just begun to rise above the horizon at this very high latitude location (84 degrees). The circular feature is likely a buried ancient crater, with the streaks indicating the prevailing wind direction blowing both sand and frost about.

On August 9, 2019 I provided an update on this monitoring, when new images of this same location were downloaded from MRO in April and June. MRO has now taken a new image of Buzzell, on October 2, 2019. Below the fold are all these images so that you can see the sublimation and disappearance of that dry ice layer over time.
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Lava-draped terrain on Mars

Lava surrounding hill and partly covering crater
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Hill surrounded by lava flows
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Cool image time! Continuing this week’s series of lava-related images from Mars (previous posts here, here, and here), today’s post is ironically the first to actually show lava flows.

The two images to the right, reduced and cropped to post here, are sections taken from an uncaptioned picture, titled “Lava-Draped Surface in Cerberus Palus” and found in the most recent download from the high resolution camera on Mars Reconnaissance Orbiter (MRO).

It is obvious why the MRO scientists gave this image this title. The hills in both pictures clearly seem to stand up like islands in a surrounding sea of frozen lava. Older craters, created prior to the lava flow, are partly obscured by the lava flows, their interior floors filled and their rims broken as the lava flooded this region.

Nor are these the only high points captured in the image that this flood of lava inundated. If you look at the full image there is even a low mound where it appears the surrounding lava flood worked its way up the hill’s gently sloping flanks only to freeze just before it completely covered the top of the mound.

The location of this image, shown by the red box in the overview map below and to the right, gives us a hint where the lava came from, though the distances involved to the nearest giant volcano, Elysium Mons, are so large it is likely that this flow is not directly linked to that volcano.
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Sinkholes on Mars

Collapse pit on Mars
Click for full image.

Cool image time! In this week’s exploration of Martian geology that is reminiscent of Earth-based lava geology, today’s image is of a collapse pit in Ceraunius Fossae, the vast region of north-south fissures found to the south of the volcano Alba Mons. The photo to the right, cropped to post here, zooms in on that pit.

The picture was part of the most recent image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO). What makes it especially interesting is the sharpness of its rim, in comparison to the collapse channel to the east. This suggests the pit is younger and fresher than the channel, and happened more recently. This also implies that the voids below the ground in which the surface is sinking are either still there, or due to on-going processes might be still be forming (like caves are on Earth).

For example, if there is underground ice, temperature changes or even thermal heat from the nearby giant volcanoes could melt that underground ice periodically, allowing it to flow and erode the surrounding material, forming voids. That this pit is located at 30 degrees north latitude, just inside the northern hemisphere band where glaciers are found, adds weight to this possibility.

The image below, reduced and rotated so that north is to the left, shows the entire sequence of collapse channels, with the more distinct pit from above in the bottom center of the picture.
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A discontinuous Martian channel

Discontinuous channel near Olympica Fossae
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Close-up of channel

Time for more strange Martian geology! As I said in my post yesterday of a cool image of skylights into what might be a Martian lava tube, this is lava week on Behind the Black. The image at the right, rotated, reduced, and cropped to post here, is similar to yesterday’s photograph, showing a line of sinks and depressions that strongly suggest the existence of an underground lava tube.

The problem with this theory is that at present we really have no idea what flowed here. It could have been lava, but it also could have been mud, water, ice, or some as yet unimagined Martian geological process.

The image was part of the most recent image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO), and was uncaptioned. The top image shows the whole channel as captured by the photograph, with the white box indicating the area covered by the second image, posted here at full resolution.

Though the overall slope of the terrain here is downhill to the west, the grade is relatively shallow, so there is no guarantee that the local slope of this particular channel follows that trend. Downhill could be either to the west or the east.

The reason I favor lava (as an amateur geologist) is the location of this channel, as shown in the overview map below and to the right.
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Skylights into Martian lava tube?

Possibly connected skylights into lava tube
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Close-up of skylights
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Cool image time! In the archive of images from the high resolution camera on Mars Reconnaissance Orbiter (MRO) I came across the uncaptioned image on the right, dubbed “Possibly Connected Lava Tube Skylight Pair in Tharsis Region.”

The top image, cropped and reduced to post here, is a wide view, showing a narrow depression oriented in a north-south direction. Downhill is to the north, with the caldera of the giant volcano Arsia Mons to the south. The white box indicates the area covered by the bottom image, cropped and expanded to post here. Within this close-up are two dark spots, each about 150 feet across.

The two dark spots surely look like small pit openings. Their alignment with the north-south depression strongly suggests that an underground lava tube is below. That this depression is also aligned with the downhill slope further reinforces this supposition.

The depression itself also aligns with the gigantic fault that runs from the northeast to the southwest through all three of the giant Tharsis Bulge volcanoes. Arsia Mons is the southernmost of the three. It is also where that fault is most clearly expressed by two dramatic breaks in the volcano’s rim in the northeast and southwest, as seen in the overview image below. Scientists have taken of lot of images of these breaks in an effort to better understand the geology and how it fits in with the formation of the volcanoes.

Overview of Arsia Mons

However, a review of the entire image archive of MRO’s high resolution camera shows that scientists have taken very few close-up images in this region. The black box in the overview map on the right is the location of this image. As of now, only three other high resolution images, as indicated by the white boxes, have been taken by MRO of this part of the volcano’s north slope.

That the skylights and depression align with this giant fault is not evidence that this supposed lava tube is linked to that fault. Lava will flow down the mountain’s slopes, fault or no fault. At the same time, the fault’s existence is also going to encourage north-south cracks and fissures, which in turn could have served as a convenient flow route for the lava. Without a closer look, on site, it is hard to know one way or the other..

I’ve located a few more lava related cool images in the MRO archive, so I’m going to make this week lava week on Behind the Black. Stay tuned!


Ice! Ice! Everywhere on Mars ice!

Ice scarp in Milankovic Crater
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In January 2018 scientists announced the discovery of exposed ice in a number scarp cliff faces found in the high-mid-latitudes of Mars.

These scarps, which have so far been found in one southern 50-55 degree latitude strip and in one crater, Milankovic, at the same latitude in the north, are important because they are one of the first places on Mars in its lower latitudes where we have found ice actually exposed and visible, not buried like the many buried glaciers very near the surface found in the 30 to 60 degree northern and southern latitude bands.

Since that press announcement, scientists have been monitoring these sites for changes, as well as expanding their survey to see if they can locate more of these scarps.

Overview map

My previous posts on this subject were mostly focused on that southern strip near Hellas Basin, as shown on the map on the right. In reviewing the most recent image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO), I noticed that the only new images of ice scarps were taken in the northern location, in Milankovic Crater, as indicated by the white dot north of Olympus Mons. The first image above shows the north-facing scarp of one of these images, cropped to focus in on the color section where, if you look close, you will see a strip of blue across the base of the scarp. That’s the ice layer, exposed as the scarp sublimates away over time from the north to the south.

over view of all MRO images taken so far in Milankovic Crater

This scarp, labeled #2 on the overview map of Milankovic Crater on the right, is located inside the crater’s eastern rim. The second image, posted below and labeled #1 on the overview map, shows a wider area of several ice scarps located on the inside of the crater’s southwestern rim.

The red boxes in the overview map indicate all the images taken by MRO inside this crater. If you go to the camera’s archive and focus in on Milankovic Crater at 54.5 degrees north latitude and 213.3 degrees longitude, you can then click on each red box to see the high resolution image. In practically every image along the crater’s inside rim can be found numerous scarps.
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Swirls and layers in Martian depression

Close-up on swirls and layers

Context of depressions in Columbus Crater
Click for full resolution image.

Cool image time! The southern highlands of Mars is littered with numerous craters, making it look from a distance not unlike the Moon. A closer inspection of each crater and feature, however has consistently revealed a much more complex history than seen on the Moon, with the origins of many features often difficult to explain.

The two images on the right, rotated, cropped, and reduced to post here, shows one such feature in the floor of one southern highlands crater, dubbed Columbus Crater. The top image is a close-up of the area shown by the box in the bottom image.

The uncaptioned full photograph was taken on May 20, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and was simply titled “Depression in Columbus Crater.” Since the photo included two large depressions, as shown in the wider view in the bottom image, I’m not sure which depression this title refers. In both cases the features do not appear to be impact craters. The top depression is far too irregular, while both do not have the upraised rims that are found on most impact craters.

I have zoomed into the top depression because of its many swirls and layers. On Earth such terrain is usually caused by either water or wind erosion, slowly carving a smooth path across multiple geological layers. Here, there is no obvious evidence of any flows in any direction. Something ate out the material in this depression, exposing the many layers, but what is not clear.

The lower depression reminds me of sinkholes on Earth, where the ground is subsiding into a void below ground The same process could have also formed the top depression.

The surrounding terrain is equally baffling, resembling the eroded surface of an ice block that has been sprayed with warm water. In fact, the entire floor of Columbus Crater appears to have intrigued planetary scientists, as they have requested a lot of images of it from MRO. So far they do not have enough of these images to produce a full map. Since the terrain appears to change drastically over short distances, it is therefore hard to fit the geology of each image together. The overall context is missing.

When I first saw this image I tried to reach the scientist who requested it in the hope he might provide me a more nuanced explanation of what we see here, but despite repeated requests he never responded. Therefore let me propose one theory, based on my limited knowledge of Martian geology.
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Weird glacial features in Martian crater

weird glacial feature in crater on Mars
Click for full image.

Cool image time! In reviewing today’s October release of new images from the high resolution camera of Mars Reconnaissance Orbiter (MRO), I came across the strange geology shown in the image to the right, rotated, cropped, and reduced to post here.

The uncaptioned image calls these “glacial features within crater.” The crater is located at 35 degrees north latitude in Arabia Terra, one of the more extensive regions of the transition zone between the northern lowlands and the southern highlands. It is also located within the northern band from 30 to 60 degrees latitude where most of the buried Martian glaciers are found.

The most abundant type of buried glaciers are called concentric crater fill (CCF) because they are found inside craters, and often show decay in a concentric manner. This weird feature likely falls into that category, though I would hardly call these glacier features concentric.

I’m not even sure if this is an impact crater. If it is, its rim has been heavily obscured, making it look instead like an irregular depression with one outlet to the south. In fact, I suspect it is possibly one of the lakes that scientists believe pepper this part of Arabia Terra and might have contained liquid water two to three billion years ago. That water would have later frozen, and possibly become covered by dust and debris to protect it.

According to present theories, Mars is presently in a period where its mid-latitude glaciers are shrinking, the water sublimating away and being transported back to its poles. The weird formations here suggest this process. Imagine what happens when you spray warm water on a big block of ice. It dissolves, but randomly to form weird shapes.

In this case the glacier is shrinking randomly where the ice has gotten exposed. In the thin Martian atmosphere, it transitions directly from a solid to a gas, sublimating into the atmosphere to leave these inexplicable shapes.


The slowly changing dunes of Mars

Map of Mars

In order to better understand the climate and geology of Mars, scientists need to study how the thin Martian atmosphere causes changes to the planet’s numerous sand dunes. To do this, they have been using the high resolution camera on Mars Reconnaissance Orbiter (MRO) to periodically snap photos of the same places repeatedly over time, to track any changes that might occur.

Recently the monthly download dump of images from MRO included one such location in the northwest quadrant of Hellas Basin, what I call the basement of Mars because it the planet’s lowest point. The uncaptioned image was taken on May 20, 2019 and was titled “Hellas Region Sand Dune Changes.” A review of past images shows that MRO has taken pictures of this location several times in the past, in 2011 and in 2017. All these images were taken during the Martian autumn season, and were taken to see if over time there were any significant changes to the dunes due to winds.

My superficial comparison of the 2011 and 2017 images does not show much obvious change. There could be small changes that my quick review did not spot, and there is also the strong possibility that the entire dune field could have shifted as a unit over those three Martian years, a change that would require a more detailed analysis beyond my technical capabilities. Click on both links, put the photographs in separate tabs, and switch quickly between them to see if you can spot any differences.

Comparing the 2011 and 2019 images however shows some significant changes, most of which I think are due to the 2018 global dust storm. Below is that comparison.
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