Tag Archives: Mars Reconnaissance Orbiter

A hanging crater on Mars

Hanging crater
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Overview

Cool image time! The image to the right, cropped and reduced to post here, was taken by Mars Reconnaissance Orbiter (MRO) on May 1, 2020, and shows a truly intriguing crater that they dub a “Crater Hanging on Mesa Wall.”

Located in Deuteronilus Mensae, a chaos region of mesas and cross-crossing canyons in the transition zone between the northern lowland plains and the southern cratered highlands, the crater literally overhangs the edge of this canyon’s cliff. The overview map to the right, with this location indicated by the red box, illustrates what this region’s geology is like.

The most likely explanation is that the impact occurred prior to the creation of the canyon, and when the canyon eroded, the material in and of this crater was more resistant, probably because the impact had packed it together to increase its density.

At the same time, the features inside both craters in the photo, as well as below them on the floor of the canyon, suggest the presence of buried glaciers, something not unlikely at the 45 degree north latitude where this crater sits.

So, here’s a guess at the geological history. First we had the impact, then during the eons of glacial ebb and flow on Mars due to wide swings in the planet’s obliquity (its rotational tilt), the canyon was cut, with that erosion leaving the crater sitting high above the canyon floor below it.

One more curious detail: The material in the canyon seems asymmetric, suggesting that the crater actually dips down toward the canyon, as if it as a unit has tilted to the east as the canyon was worn out below it.

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Two wedding cakes on Mars

Tall wedding cake on Mars
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It it time for two cool Martian images from the high resolution camera on Mars Reconnaissance Orbiter (MRO). Though both show features that are similar and likely had some comparable geological origins, they are located in two very different places on Mars and thus also had very different histories.

What makes them fun is how much both resemble classic tall wedding cakes, though the second has unfortunately fallen down and is no longer eatable.

The first, cropped on the right to post here, was taken on May 18, 2020, and is described by the science team as a “Tall Layered Mesa in Crater in Deuteronilus Mensae.” Deuteronilus Mensae is in the transition zone between the northern lowland plains and the southern cratered highlands, and being in the high mid-latitudes (42 degrees north) shows a lot of evidence of buried and eroded glaciers. Many of these glaciers are found inside craters.

What caused this layered mesa however to form is beyond me. It is taller than the crater in which it sits, as well as the surrounding terrain. A glacier would settle into the lowest regions, and would not last if exposed above the rim like this is. Its height suggests that the surrounding terrain was once much higher, and has been eroded away. Yet if so, why does this mesa also sit inside a depression?

The second “wedding cake” is even more intriguing, though less baffling.
» Read more

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More strange terrain in the Martian “Death Valley”

More strange terrain in Hellas Basin
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Today’s cool image, rotated cropped, and reduced to post here, might show what the science team for the high resolution camera of Mars Reconnaissance Orbiter (MRO) have labeled “strange banded terrain”, but anyone who has spent any time perusing images of Hellas Basin, what I have labeled the basement of Mars because it has the lowest elevation on the planet, will recognize the features.

They might be inexplicable, but for Hellas Basin they are entirely familiar. Just take a look at some of my earlier posts:
» Read more

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Enigmatic layering and chasms on Mars

Enigmatic layering and chasms
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Overview map

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on April 28, 2020 by the high resolution camera on Mars Reconnaissance Orbiter. (MRO). The science team entitled it “Enigmatic Uplifts in Echus Montes,” indicating a sense of bafflement on their part about this geology.

The features here are certainly somewhat puzzling. At first glance the terrain is reminiscent of Martian chaos terrain, mesas cut by canyons in an almost random pattern. As I explained at the link,

Chaos terrain is typically a collection of mesas separated by straight-lined canyons. It is found in many places on Mars, most often in the transition zone between the southern highlands and the northern lowlands where an intermittent ocean might once have existed. It is believed to form by erosion, possibly caused by either flowing water or ice, moving along fault lines. As the erosion widened the faults, they turned into canyons separating closely packed mesas. With time, the canyons widened and the mesas turned into a collection of hills.

What makes this particular image puzzling however is that there seem to be multiple layers of mesas and canyons. Look at the top of the rectangular mesa in the upper middle of the image. It appears to have its own miniature chaos terrain on its plateau. Somehow that first layer of chaos was abandoned when the more prominent larger canyons started to form around it.

The location of this feature is indicated by the black cross on the overview map to the right. It is in the middle of the large and wide northward trending part of the giant valley dubbed Kasei Valles. And as usual, knowing the location helps explain what we are seeing.
» Read more

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Deciphering the strange geology of Mars — or anything!

Eroding Medusae Fossae Formation ash deposits
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Today’s cool image is for once not taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Instead, the image to the right, cropped and reduced to post here, was taken by Mars Odyssey on April 5, 2020, and shows the scouring and erosion caused by winds over many eons in a region dubbed Zephyria Planum. (Note that the image might fool your eye. Sunlight is coming from the east, and the rough terrain at the top is higher than the smooth plain at the bottom.)

Years ago, when I first started to rummage through the archives of images from the various Mars orbiters, I would have seen this image and posted it because I was completely baffled by what I saw, and thought that mystery made it worth showing to the public. Since then my incessant probing of research papers as well as asking a lot of questions of scientists has taught me a lot more about what scientists now surmise of the Martian geology. This greater knowledge in turn makes it possible for me to look at an image like this and immediately make a reasonable guess as to an explanation. This photo, while still containing much that is mysterious, is no longer completely baffling to me.

This willingness to ask questions and dig deeper is fundamental to all things. To have a deeper understanding and not simply guess about any subject, you always have to recognize that your assumptions are likely wrong, and that to learn anything you have to repeatedly ask what I call “the next question.” The first answer will force you to recognize that your first guesses are wrong, raise more questions, which in turn will lead to more questions, and then more questions, and so forth.

Whether I am researching Mars or early space history or politics, this rule always applies. Don’t leap to a conclusion. Think it possible you could be wrong. Ask the next question. And the next. You will repeatedly find that what you thought you knew was not correct, and in the end you will gain a deeper understanding of what is actually known about any subject, as well as what is unknown. And knowing the unknowns is probably the most important thing you can learn.

To gain a better understanding of today’s particular image, our first questions must start with context. Where is this feature on Mars? What is the surrounding history of that location? And what is already known about this place?

The location immediately reveals a great deal, as shown in the overview map below.
» Read more

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Isidis Basin, on whose margin Perseverance will roam

Pedestal craters in Isidis Basin
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Overview map

Today’s cool image to the right, cropped and reduced to post here, highlights the floor of one of Mars’ largest basins, dubbed Isidis Planitia, and located at the transition zone between the planet’s northern lowland plains and the southern cratered highlands.

The overview map below of Isidis Basin provides some context. The white box shows where this particular image is located. Jezero Crater, indicated by the red circle (which is also about the size of the crater), is where the rover Perseverance is going to land and roam come February 2021, should all go well. For scale, Isidis is about the size of the eastern half of the United States. If Chicago was located at Jezero Crater, Baltimore would be on the basin’s eastern edge, at around 4 o’clock.

This particular section of the full photo, taken on April 5, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), shows many features very typical of the floor of Isidis Basin, which also immediately reveal a great deal about its possible history.

In this small snippet we can see what at first glance appear to be pedestal craters standing up like mesas, with ordinary craters scattered about on that lower surrounding terrain. Clearly, if these are pedestal craters they had to have been created first, and then over a very long time erosion processes ate away at that plain, leaving these pedestals (which had become resistant to erosion because the impact had packed their material together and made it harder) behind as mesas.

Then, after this period of erosion was complete enough additional time was required for at least one or two rounds of cratering to occur, leaving behind the many more younger craters on the plain floor, many of which are now partly buried by dust and sand.

The problem is that these mesas are almost certainly not pedestal craters, despite their appearance. » Read more

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Fading Martian slope streaks

Fading Martian slope streaks
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Cool image time! I’ve covered the topic of the mysterious slope streaks on Mars previously in great detail (see here and here). Essentially they are generally dark streaks (but sometimes light) that appear randomly on slopes and then fade over time. Unlike recurring slope lineae, another changing streak found on Martian slopes, the coming and going of slope streaks is not tied to the seasons. They can appear at any time in the year, and will take several Martian years to fade away.

The image to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on March 26, 2020. It shows numerous slope streaks down the eastern interior rim of a crater in the transition zone between the northern lowlands and the southern cratered highlands in a region dubbed Arabia Terra.

Though I can find no previous high resolution image of this crater to measure any temporal changes, you can clearly see that this slope has experienced many streaks over time, with some darker than others. The different shades suggest that the lighter streaks are older and have faded, with the darker streaks more recent events.

At the moment there is no strong consensus on the causes of these streaks. As one science paper noted, “The processes that form slope streaks remain obscure. No proposed mechanism readily accounts for all of their observed characteristics and peculiarities.” We know they occur in equatorial regions and dusty locations, and that they are triggered by some disturbance at the topmost point of the streak, which then causes a chain reaction down the slope. Other than that, the facts are puzzling, and suggest that these streaks are a phenomenon wholly unique to Mars.

The crater itself, located at 24 degrees north latitude, has some other mysteries. The features on its floor, for instance, are very puzzling. Though suggestive of the buried glaciers found in many craters in the mid-latitudes, this crater is a bit too far south. Maybe its higher altitude allows for some ice to remain here? Then again, the features on that floor might have nothing to do with ice. Maybe we are looking at sand carved by wind? Or hardened mud that was once wet?

I am merely guessing, a dangerous thing to do when one’s knowledge is limited. Then again, it’s fun, so please join in with your own guesses.

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An exposed dry waterfall on Mars

An exposed dry waterfall on Mars
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Close overview map

Wide overview map

Cool image time! The photo to the right, cropped and reduced to post here, was taken on April 30, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Uncaptioned, the science team titled the release as a “Cataract in Osuga Valles.”

To understand what we are looking at it is necessary to also see a wider view, as provided by the context map below and to the right. As you can see, this image straddles across the canyon called Osuga Valles, and heads downstream to the east. It also shows a point where the grade of that canyon suddenly drops. If water ever flowed here this place would have been the location of a truly spectacular waterfall.

More likely, these cataracts mark the location where sometime in the past a glacier had flowed down this valley, cutting a path until it broke out into the large and wide dead end area that appears to have no clear outlet. For some reason at this point the downhill grade of this canyon suddenly dropped, with the glacier following that sudden steep drop.

There is no glaciers here now, as this location is at 14 degrees south latitude, too close to the equator for any ice to remain close to the surface. Instead, dust dunes remain as the only feature flowing down through these cataracts.

The second overview map provides further context, showing the location of Osuga Valles relative to nearby Valles Marineris, the largest known canyon system in the solar system. Whatever process formed that gigantic canyon system certainly was a factor in forming Osuga Valles. The details however are not yet understood with any certainty. All we presently have are theories.

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The strange squashed ridges at the basement of Mars

Squashed ridges at the basement of Mars
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Overview map

Cool image time! The photo on the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on April 9, 2020, and shows the very weird and very packed ridges and layers that are found routinely at the deepest part of Hellas Basin, what I have dubbed the basement of Mars.

Be sure to click on the image to see the full photograph. There’s lots more strangeness to see there. And be sure to read my post in the second link, which highlights a similarly strange set of packed ridges, and where I note:

This is the basement of Mars, what could be called its own Death Valley. The difference however is that unlike Death Valley, conditions here could be more amendable to life, as the lower elevation means the atmosphere is thicker.

The context map to the right shows Hellas, with the location of today’s image indicated by the white box, close to basin’s lowest point, more than five miles below the basin’s rim. Overall the Hellas Basin is about the size of the western United States, from the Mississippi River to the Pacific Ocean. It is believed that the entire basin was created by a single gigantic impact that occurred about four billion years ago when the solar system’s inner planets were undergoing what has been labeled the Late Heavy Bombardment.

The specific process that formed these ridges, dubbed honeycomb terrain by scientists, remains unknown however. There are of course theories, none of which are very convincing. Here’s mine, as outlined in the previous post:
» Read more

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Thar’s ice in them Martian hills!

Icy mountains in Erebus Montes?
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Overview map of Starship landing site images

Cool image time! Today we return to the Erebus Mountains, located just to the west of SpaceX’s prime candidate landing site for Starship on Mars. The photo to the right, taken on April 4, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and rotated, cropped, and reduced to post here, shows one particular area between the peaks in those mountains, and also happens to be very close to what I have labeled image #1 in SpaceX’s Starship landing site photos.

The second image below and to the right shows an overview map of this region, with the SpaceX photos indicated by the numbered white boxes and the location of this image indicated by the red box, right next to image #1. The black boxes were images that SpaceX had obtained from MRO earlier, when it was first planning to send a Dragon capsule to Mars using a Falcon Heavy, a project the company has put aside in its focus on building Starship.

To my eye, everything in the first image above reeks of an icy, glacial terrain. I certainly am guessing, but it is an educated guess based on looking at numerous similar images in this region (see here and here, ) as well as in the nearby Phlegra mountains to the west. I also base my guess on what I have learned interviewing planetary scientists who are studying these images. The reasonableness of this guess is further strengthened in that the location is at 39 degrees north latitude, dead center in the mid-latitude bands where scientists have found evidence of numerous buried glaciers.

If Starship lands just to the east of the Erebus Mountains, the first colonists will likely not only have water available at their feet close to the surface in the flat lowland plains, if they find that resource insufficient they will need only climb uphill a bit into these hills to dig out as much ice as they could ever need.

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A Martian crater with a straight edge

A mis-shapened crater on Mars
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Cool image time! The image to the right, cropped and reduced to post here, was released today by the science team of the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small Martian crater whose northern rim for some reason is flattened into a straight line. Such a crater is rare, since almost all craters rims are round, even in the case of a low angle impact. The cause is unknown, though there are theories. From the caption, written by Ingrid Daubar of the Lunar and Planetary Laboratory in Arizona:

One possibility is that there was a zone of joints or faults in the crust that existed before the impact. When the impact happened, the crater formed along the straight line of these faults. Something similar happened to Meteor Crater in Arizona. Our image doesn’t show any faults, but they could be beneath the surface.

Perhaps some sort of uneven collapse changed the shape of the crater. There are piles of material on the crater’s floor, especially in the northwest and northeast corners. If those piles fell down from the rim, why did it happen there and not in other places? This crater is near the size where larger craters start to show wall slumping and terraces, so this type of collapse could be occurring unevenly.

The crater is located in the southern cratered highlands of Mars, at about 32 degrees latitude. At that latitude, it is also possible that some past glacial activity could have misshapen this crater, though I have no idea how. The crater itself does not appear to have any glacial material in it.

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Weird central peak in Martian crater

Textured central peak in Martian crater
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Cool image time! The photo to the right, cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on March 18, 2020. It shows a very strange central peak in a crater on Mars. Not only does this peak stick out like a sore thumb in a relatively flat crater floor, its surface is strangely textured, patterned with what look like scallops.

The overview map below shows the area covered in the crater by the full image.

My guess is that the peak is the final impact melt from the original impact. Think of a pebble thrown into a pond. You get ripples (the crater rim) as well as an upward drop of water (the central peak). Unlike pond water, the material in a crater freezes quickly, leaving both the ripple and the upward drop frozen in place.

Close overview of crater

This peak however also reminds me of volcanic cones found in the American southwest, the remnant cone of a much larger volcano that has long ago eroded away.

The textures might be evidence of that erosion process, as they resemble scallops that wind and water erosion can cause on rock faces.

We also could be seeing dunes on the slopes themselves, though I think this is unlikely. This crater is on the edge of the vast Medusae Fossae Formation, the largest volcanic ash deposit field on Mars, as shown by the white cross on the overview map below. Thus, being on the edge of this ash field there is a lot of available dust and sand that can pile up on these slopes.

Wide Overview map

Still, the sunlight side of the ridge suggests the scallops are in bedrock, not sand dunes. And to assign their origin to either wind or water or ice erosion I think is a stretch.

So while the peak is probably the frozen melt remains of the original impact, the scallops are a geological mystery that needs unraveling.

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Amazing layers

Bedrock layering in Holden Crater
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Cool image time! The science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) today released a cool captioned image entitled “Exquisite Layering”, showing a place on the floor of Holden Crater where the dust and sand that normally covers most of the Martian surface has been wiped away, cleared off because these layers are on higher sloping terrain.

The image to the right, cropped to post here, focuses in on that exposed layering, believed to be sedimentary and must have therefore happened in the eons following the impact that caused the crater.

Overview map

The overview map to the right shows with the red box the location of this layering inside Holden Crater. The map also illustrates why this crater was considered a candidate landing site for Curiosity. Like Gale Crater, it has evidence — the large meandering canyon system flowing into the crater — that suggests it had once been filled with a water lake. These sedimentary layers support that hypothesis, suggesting that this lake was intermittent. Each time it refilled and then dried up, it laid down a new deposit of those sedimentary layers.

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More pits found on Mars

Pit near Hephaestus Fossae
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Overview map

Since 2018 I have made it a point to document every new pit image taken on Mars by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The list of can be found at the bottom of this post.

In the most recent release from MRO, a number of new pits were photographed. All continue to suggest that Mars has a lot of underground voids, some caused by lava flow, some by tectonic activity, some by water ice erosion, and some almost certainly caused by processes we don’t yet know. The images also suggest that we have only identified a small fraction of those underground voids.

The first image to the right, cropped to post here, shows the one new pit in the northern lowlands of Utopia Planitia, near a series of meandering channels and canyons dubbed Hephaestus Fossae and Hebrus Valles.

This appears to be the fifth such pit found in this region. Previously I had documented the first four. The overview map to the right adds this fifth pit. Note how the pit is much closer to the head of Hephaestus. In the full image you can see fissures both to the north and south, as well as many nearby aligned depressions, suggesting the existence of more underground passages, some possibly linked to voids under this very pit.

The pit itself seems filled, with no apparent side passages, though to the southwest there might be something leading off in the shadows.

The overall terrain in this region, including these pits, the fissures, and the many aligned depressions, strongly suggests a lot of underground voids. As I noted in 2019:
» Read more

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A shadowed ice patch on Mars

A shadowed ice patch on Mars
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Cool image time! The evidence coming back from Mars in the past two decades has increasingly suggested that there is a lot of water in that planet’s mid- and high latitudes. In the mid-latitudes the evidence suggests that ice is locked in a lot of buried and inactive glaciers that were laid down during periods when the planet’s rotational tilt, its obliquity, was greater so that the annual seasons were more extreme. During those times the mid-latitudes were colder than the poles, and water was being transferred from the poles to those mid-latitudes.

The image to the right appears to be more such evidence. Taken on March 21, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and cropped and brightened by me to bring out the important details, it shows what looks to be a distinct patch of ice on the south-facing slope of the rim of a large crater. Since this crater is in the southern mid-latitudes (34 degrees south), that south-facing slope generally gets much less sunlight, even in the summer, so any remaining buried glacial ice on that slope will linger for a longer period.

Think of the lingering ice and snow patches on shadowed locations on Earth. Because the Sun does not directly shine on them, they will be the last patches to melt away.

What I think is likely important about this patch are the exposed layers along its edge. These are the spots that are melting first, as they are where the ice is exposed, unprotected by a layer of dust and debris. It is also here that we have a window into that geological history. Even at this resolution you can see that the ice was laid down in layers, meaning that it contains evidence of those repeated climate cycles produced by Mars’ shifts in obliquity.

Those layers even seem to show the same sharp and sudden change from brighter and dirtier layers, as seen in the layers of the north pole ice cap, that occurred about 4.5 million years ago.

How tantalizing. The entire climate history of Mars is sitting there for us to decipher. We need only drill a few core samples and voila! the pieces of that history will start to fall into place.

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The edge of an eroded buried Martian glacier

The edge of an eroded buried Maritian glacier
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Overview

Cool image time! The image to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on April 6, 2020.

The image shows the dying edge of a debris flow coming down from a mesa, the edge of which can be seen as the dark slopes in the upper left. The white arrows point up slope. It is located in the chaos terrain of a mid-latitude region called Deuteronilus Mensae, in the transition zone between the southern highlands and northern lowlands, where many such glacial-like features are found. I featured a similar nearby glacial edge only two months ago, where the image showed the glacier’s break up and collapse at its edge.

Here, the debris flow isn’t breaking up so much as crumbling away, its edge a line of meandering depressions, with the uphill slope covered with many knobs and tiny depressions, reminiscent to me of the many features I see in caves, where the downward flow of water shapes and erodes everything to form cups and holes and knobs, all the same size. If you click on the full resolution image and zoom into that debris slope and then compare it with the linked cave formation photo, you will see the resemblance.

We are almost certainly looking at a buried inactive glacial flow coming off that mesa, though it appears to be eroding at its foot. The overview image to the right shows the context, with the red dots indicating this image as well as similar features in adjacent mensae regions (featured in the linked images above). While the chaotic and rough terrain found along this transition zone does not make them good first settlement sites, the ample evidence of vast reservoirs of buried ice, combined with a variety of topography, will likely someday make this good real estate for those living on Mars.

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The blobby wettish flows of Mars

flow-like feature in Utopia Planitia
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Cool image time! Rather than talk about shut downs, lying politicians, and our tragically fear-filled society, let’s go exploring on Mars. The image to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on February 8, 2020. Dubbed a “Flow-Like Feature within the Adamas Labyrinthus”, it shows what appears to be a very distorted and eroded pedestal crater surrounded by strange triangular-shaped flow features.

It also shows, as does much other research, that the northern mid-latitudes of Mars have a lot of frozen water, much of it buried very close to the surface.

Assuming this is a pedestal crater (which it might not be), this feature has to be very old. Pedestal craters require age, as to stand out above the surrounding terrain a lot of time is needed to erode that terrain away. This age is confirmed by the bunch of newer craters on top.

At the same time, the partially filled small crater near its bottom, as well as the soft eroded depressions on top, suggest that much of this surface has been reshaped by more recent flows, changing its shape over time.

The surrounding triangular flows probably occurred at the original impact, and suggest that there is ice near the surface, making the material here act almost like wet mud when heated. Since this location is right in the middle of the mid-latitude bands where scientists have found lots of evidence of buried glaciers and ice near the surface, this supposition seems reasonable.

The overall location provides some further context.
» Read more

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A relaxed crater on Mars

A relaxed crater on Mars
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, shows what the science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) call a “Relaxed Crater.” This particular image was taken in July 2014. A more recent photo was taken in March 2020 to create a stereo pair, but because this older image shows more of the crater I decided to highlight it.

The crater is considered relaxed because it is very shallow and appears as if, after impact, some process caused the interior to in-fill with material even as the rim became less pronounced and degraded (as explained in this paper [pdf]). The process could have involved either molten magma or melted ice. As this crater is located in the northern highlands to the southwest of Erebus Mountains, in a region that research has consistently suggested has a great deal of ice just below the surface, the latter seems likely. This assumption is further reinforced in that the crater is also located in the mid-latitudes where scientists have found a lot of craters they think are filled with buried glaciers. This certainly seems the case here.
» Read more

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The eroding edge of Mars’ largest volcanic ash field

Eroding yardangs at the edge of Mars' largest volcanic ash field
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Cool image time! In the regions between the biggest volcanoes on Mars is the Medusae Fossae Formation, a immense deposit of volcanic ash that extends across as much surface area as the nation of India. As planetary scientist Kevin Lewis of Johns Hopkins University explained to me previously,

In general, much of the [formation] seems to be in net erosion now, retaining very few craters on the surface. …One hypothesis is that this long term erosion, since it’s so enormous, is the primary source of the dust we see covering the much of the planet’s surface.

The image above, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on January 25, 2020. It shows one very small area at the very edge of the Medusae ash deposit, in a region where that deposit is clearly being eroding away by the prevailing southeast-to-northwest winds. The mesas of this ash that remain are called yardangs, their ash more tightly pressed together so that it resists erosion a bit longer than the surrounding material.

In the context map below the location of these yardangs is indicated by the white cross, right on the edge of the Medusae ash field.
» Read more

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The edge of Mars’ north polar ice cap

The scarp face of the Martian north polar ice cap
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on December 29, 2019 by the high resolution camera of Mars Reconnaissance Orbiter (MRO) and shows the many-layered scarp face of the Martian north polar ice cap. I have also rotated the image so that north is at the top. The overall height of this scarp is quite high, more than 3,500 feet.

There are a number of very cool features in this image. For example, note what at first look like puffs of clouds just below the contact between the bright and dark layers. I count almost two dozen, with the largest near the center. They are not cloud puffs, however, but areas scoured by past avalanches. According to Patricio Becerra at the University of Bern in Switzerland,

An image from a few years ago shows evidence for the same patches, so they likely happened a while back. When the avalanches or “block falls” occur, they scour the Basal Unit [the dark layer] and break up the exposed surface, causing a brighter/cloudier appearance of the ground than the undisturbed parts.

Avalanches on the scarps of the North Pole icecap occur in great numbers at the beginning of every Martian summer. As sunlight hits the scarp, it causes the carbon dioxide frost layer that settled on the cap during the winter to sublimate away as vapor, and like the freeze-melt cycle on Earth, this sublimation disturbs any unstable ice boulders on the scarp face.

During the early Martian summer, images from MRO routinely capture many such avalanches. Scientists think there could be hundreds to thousands every summer. In many ways, this is similar to the large pieces of ice that routinely calf off the foot of glaciers here on Earth, and that tourists take cruise ships to see in the inside passage of Alaska.

For context, the overview map below indicates with a gold cross where on the icecap’s edge this image is located. The red and pink areas indicate the vast dune fields that surround the icecap.
» Read more

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Curiosity and other Mars orbiters threatened by budget cuts

The proposed budget for NASA in the Trump administrations 2021 budget request to Congress includes significant budget cuts to both Curiosity and several Mars orbiters needed to act as relay communications satellites.

The White House’s 2021 federal budget request allocates just $40 million to the mission, a decrease of 20% from the rover’s current funding. And that current funding is 13% less than Curiosity got in the previous year, said Curiosity project scientist Ashwin Vasavada, of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

If the 2021 request is passed by Congress as-is, Curiosity’s operations would have to be scaled back considerably. Running the mission with just $40 million in 2021 would leave unused about 40% of the science team’s capability and 40% of the rover’s power output, which comes from a radioisotope thermoelectric generator (RTG), Vasavada said.

In addition, the proposed budget will require a 50% reduction in imaging by Mars Reconnaissance Orbiter, the end to the Mars Odyssey orbiter, and a significant but unspecified reduction in the use of the MAVEN orbiter.

I reported these facts back in March but there is no harm in noting them again.

The question is not whether there should be cuts at NASA. Considering the overall federal debt and annual budget deficit, NASA’s budget should be cut. The question is what to cut. The planetary program, probably NASA’s most successful program, is certainly not the program to cut. Instead, the Trump administration should be cutting the waste and badly run programs, like SLS, that spend billions and accomplish nothing.

If Congress and Trump did this, they could cut NASA’s total budget and still have plenty left over for the commercial manned program — including going to the Moon — and also increase the budget to the planetary program. I’ve been saying this since 2011, and nothing has happened in the past decade to change that conclusion.

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A Martian lava flood plain

A Martian lava flood plain?
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Cool image time! The photo to the right, cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on March 2, 2020, and shows some inexplicable shallow pits and depressions in the middle of a relatively flat and featureless plain.

Make sure you click on the image to see the full photo. Though the plain looks remarkably smooth, a handful of dark splotches are scattered about, almost all of which occur on top of small craters.

What causes these depressions? The MRO team calls this “Landforms near Cerberus Tholi.” Cereberus Tholi is a a collection of several indistinct and relatively small humps that scientists think might be shield volcanoes.

More clues come from the overall context.
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Stucco on Mars

Stucco on Mars
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As a break from Wuhan flu madness I give you another cool image, cropped and reduced to post here, taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I call this stucco on Mars because that is exactly what it looks like. It is as someone laid down a layer of damp concrete and then ran over it roughly with a trowel to raise the knobs scattered across the surface.

The uncaptioned MRO image calls this “Aligned Mounds with Broad Summit Pits”. Those aligned mounds run across the top of the image. I suspect they are pedestal craters, left over because the impact had packed and hardened the crater so that it resisted erosion as the surrounding terrain was worn away.

The two insets, posted below at full resolutoin, focus on one of those pedestal craters as well as the distinct mesa at the bottom of the photo.
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Rock droplets hitting a Martian plain

Depressions in Amazonis Planitia
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Cool image time! The photo the right, rotated, cropped, and reduced to post here, is not only cool, it contains a punchline. It was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on February 11, 2020 and shows one small area between two regions in the northern lowlands of Mars, dubbed Amazonia Planitia (to the south) and Arcadia Planitia (to the north) respectively.

This region is thought to have a lot of water ice just below the surface., so much in fact that Donna Viola of the University of Arizona has said, “I think you could dig anywhere to get your water ice.”

I think this image illustrates this fact nicely. Assuming the numerous depressions seen here were caused by impacts, either primary or secondary, it appears that when they hit the ground the heat of that impact was able to immediately melt a wide circular area. My guess is that an underwater ice table immediately turned to gas so that the dusty material mantling the surface then sagged, creating these wider circular depressions.

Of course, this is merely an off-the-cuff theory, and not to be taken too seriously. Other processes having nothing to do with impacts could explain what we see. For example, vents at the center of these craters might have allowed the underground ice to sublimate away, thus allowing the surface to sag.

So what’s the punchline?
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Strange terrain in the Martian lowlands

Strange terrain in northern lowlands
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Cool image time! The science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) yesterday released a new captioned image, entitled “Disrupted Sediments in Acidalia Planitia”, noting that the photo

…shows a pitted, blocky surface, but also more unusually, it has contorted, irregular features.

Although there are impact craters in this area, some of the features … are too irregular to be relic impact craters or river channels. One possibility is that sedimentary layers have been warped from below to create these patterns. The freezing and thawing of subsurface ice is a mechanism that could have caused this.

The image to the right, rotated, cropped, and reduced to post here, shows the lower quarter of the full image. While in some areas it does appear as if changes below the surface caused the surface to warp and collapse, as suggested by the caption, in other places it looks more like the top layers themselves sublimated away without disturbing what was below them.

Note for example the pits near the bottom of the photograph. They clearly show sedimentary layers on their cliff walls, including the tiny circular mesa in the middle of the rightmost pit.

If these pits were collapsing from below, their cliffs would be more disturbed, because it would have been those lower layers that sublimated first. Instead, it appears that the top layer disappeared first, followed by each lower layer, one by one.

This region of strange terrain is located in the middle of the northern lowland plains. The overview map below gives some context, with the small white box showing this photo’s location.
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Baby Martian volcanoes

Cratered cone near Noctis Fossae
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Cool image time! I came across this strange feature shown on the right in my normal rummaging through the archive of the high resolution camera on Mars Reconnaissance Orbiter (MRO). The photo, rotated, cropped, and reduced to post here, focuses on what they label a “cratered cone.”

The immediate thought is that this is a volcano cone, and the craters at its peak are not impact craters but calderas. In science however such a knee-jerk conclusion is always dangerous. For example, this might instead be a pedestal crater, where the surrounding terrain was worn away over eons, leaving the crater sitting high and dry.

It is therefore important to look deeper to determine what origin of this feature might be.

First, its location, as shown in the overview map below, provides us our first clue.
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Seasonal avalanches in Martian dune gully

Seasonal changes in Martian dune gully
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The science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) today released a very cool pair of images, taken a Martian year apart, showing some significant changes that had occurred during that time in a large sand dune slope inside a crater. On the right is that pair, reduced and with the top image slightly lightened to bring out the features. As they wrote in the caption,

One large gully in particular has had major changes in every Martian winter since [MRO’s high resolution camera] began monitoring, triggered by the seasonal dry ice frost that accumulates each year.

This time there was an especially large change, depositing a huge mass of sand. The sand divided into many small toes near its end, or perhaps many individual flows descended near the same spot. Additionally, a long sinuous ridge of sand was deposited. This could be a “levee” that formed along one side of a flow, but there is not much sand past the end of the ridge, so it might also be the main body of a flow.

Nor is this dune gully the only active one in this crater, dubbed Matara Crater, located in the southern cratered highlands at about 50 degrees south latitude. If you look at the full image and compare it with an image from 2009 there are many changes across the entire slope field that extends a considerable distance to the north and south of the cropped section shown above.

At this latitude atmospheric carbon dioxide settles as frost during the winter, then sublimates away with the coming of spring. The freeze-sublimation process disturbs the sand each year, causing these avalanches.

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The icy Phlegra Mountains: Mars’ future second city

Icy glaciers in the Phlegra Mountains of Mars
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About a thousand miles to the west of the candidate landing site for SpaceX’s Starship spacecraft rises a massive mountain wall dubbed the Phlegra Mountains, rising as much as 11,000 feet above the adjacent lowland northern plains.

Phlegra Montes (its official name) is of special interest because of its apparent icy nature. Here practically every photograph taken by any orbiter appears to show immense glacial flows of some kind, with some glaciers coming down canyons and hollows [#1], some filling craters [#2], some forming wide aprons [#3] at the base of mountains and even at the mountains’ highest peaks [#4], and some filling the flats [#5] beyond the mountain foothills.

And then there are the images that show almost all these types of glaciers, plus others [#6]. Today’s cool image above is an example of this. In this one photo we can see filled craters, aprons below peaks, and flows moving down canyons. It is as if a thick layer of ice has partly buried everything up the highest elevations.

None of this has gone unnoticed by scientists. For the past decade they have repeatedly published papers noting these features and their icy appearance, concluding that the Phlegra Mountains are home to ample buried ice. SpaceX even had one image taken here [#3] as a candidate landing site for Starship, though this is clearly not their primary choice at this time.

The map below gives an overview of the mountains, their relationship to the Starship landing site, and the location by number of the images listed above.
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A river canyon on Mars?

Cool image time! In the most recent download of new images from the high resolution camera of Mars Reconnaissance Orbiter (MRO) were two photos, found here and here, that struck me as very intriguing. Both were titled simply as a “Terrain Sample” image, which generally means the picture was taken not because of any specific request by another scientist doing specific research but because the camera team needs to take an image to maintain the camera’s proper temperature, and in doing so they try to time it so that they can do some random exploring as well.

As it turned out, the two images were more than simply random, as they both covered different parts of the same Martian feature, what looks like a branching dry dendritic river drainage. Below is a mosaic of those two images, fit together as one image, with a wider context image to the right, taken by Mars Odyssey, showing the entire drainage plus the surrounding landscape with the white arrow added to help indicate the drainage’s location.
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Weird flat plateau on Mars

Weird flat plateau on Mars
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Cool image time! The image to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on December 15, 2020, and was actually a follow-up observation from an earlier image taken by the camera on Europe’s Trace Gas Orbiter (TGO), according to Dr. Livio Tornabene of the University of Western Ontario. As he explained in an email:

The team is rather polarized with their verdict on what exactly the feature is… while at first glance it appears to be a lava flow, it very well could be that these deposits eroded to yield this flow/lobate like appearance and isn’t lava at all. So as someone that is both involved with [TGO] and [MRO], I noticed that the lobate feature causing quite the debate had no coverage from [MRO].

It appears that some scientists think that instead of lava, this is a mud flow. Research presented [pdf] during the 2019 Lunar & Planetary Conference in Texas found evidence that mud could flow like lava under the right conditions.

At this point neither Tornabene nor anyone working on the TGO team have yet analyzed this new MRO image to see if they can answer this question. That this feature is located in a region just to the southeast of Marineris Valles where there is evidence both of volcanic activity and sedimentary deposition, makes answering the question even more challenging.

The data from TGO indicated [pdf] that the plateau was about 30 to 65 feet thick. Based on crater counts the age is thought to be between 1.6 to 1.9 billion years old.

What struck me about the plateau is that though it really does look like a flow, it also appears remarkably flat and smooth. Even more puzzling is that, according to the TGO paper, the plateau slopes downhill very gently (a 1% grade) to the south, not to the north as suggested by the shape of the flow. Maybe later geological events tilted the entire feature after it solidified, thus changing the grade?

Meanwhile that channel near the bottom of the image crosses through the grade and the flow, as if it was cut after the flow was placed. In other words, the flow and channel were formed separately, at different times.

Ah, the mysteries of planetary geology. If only we could just go there with a geologist’s hammer. These questions would then be so much more simple to answer.

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