Twisted and tilted bedrock in Martian crater

tilted strata in Martin Crater
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Cool image time! The photo to the right, rotated cropped, and reduced to post here, is only a small example of the strangely tilted and twisted strata in the central peak region of 38-mile-wide Martin Crater on Mars. The full image shows more.

The picture was taken on January 12, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The section I’ve cropped out shows a series of stratified strata that are are not only significantly tipped from the horizontal, but have also been bent and deformed.

The crater itself is located about 260 miles south of Valles Marineris, as shown on the overview map below.
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A visit to Cydonia on Mars

Strange geology in Cydonia on Mars
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Cool image time! The Cydonia region on Mars, located at around 30-40 degrees north latitude in the northern lowland plains just beyond the transition zone up to the southern cratered highlands, is well known to many on Earth because it was here that the Viking-1 orbiter took a picture of a mesa that, because of the sun angle, made its shadows resemble a face. Thus was born the “Face on Mars” that consumed the shallow-minded among us — and thus the culture, media, and Hollywood — absurdly for decades, until Mars Global Surveyor took the first high resolution image and proved without doubt what was really obvious from the beginning, that it was nothing more than a mesa.

Cydonia however remains a very intriguing region of Mars, mostly because it is home to a lot of strange geology, as shown by the photo to the right, rotated, cropped, and reduced to post here. Taken on January 16, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), it shows some of that strange and inexplicable geology.

While Cydonia is inside that 30-60 degree latitude band where MRO has imaged numerous glacial-type features, I do not know if many such features have been found there. Except for the pits and depressions in the photo’s lower right — which suggest decay in an ice sheet — little else at first glance in the picture clearly invokes any of the obvious glacial features one comes to expect. There appear to be what might be lobate flows in the image’s center going from the west to the east, but if they are glacial, they are so decayed to as leave much doubt.

The overview image below shows where Cydonia is on Mars, and helps explain partly what is found here.
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Volcanic badlands on Mars

Volcanic badlands on Mars
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on January 29, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a particularly ugly region of rough terrain located about 900 miles to the southwest of the giant volcano Arsia Mons, the southernmost of the chain of three giant volcanoes between Olympus Mons and Valles Marineris. The picture sits inside the floor of a very old and degraded 185-mile-wide crater dubbed Koval’sky.

The section I cropped out was picked at random, because the entire full image looked like this. Though only a handful of images have been taken of the floor of Koval’sky Crater by MRO’s high resolution camera, all show similar rough terrain. In June 2017 the MRO science team posted one of those few such photos with the following caption:
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SpaceX narrows Mars landing site for Starship to four prime locations

The prime and secondary Martian landing sites for Starship

Capitalism in space: During this week’s 52nd Lunar and Planetary Science Conference, one poster [pdf] caught my eye as something significant. It was titled “SpaceX Starship Landing Sites on Mars.” The map to the right is figure 1 from that poster, annotated slightly by me based my earlier stories about SpaceX’s use of the high resolution camera on Mars Reconnaissance Orbiter (MRO) to research potential Martian landing sites for its Starship spacecraft. The stars indicate MRO images, most of which were described and linked to in my last major post about this SpaceX effort in November 2019.

The red spots covering some stars are the big story: SpaceX has narrowed its choice for its Starship landing site to four prime locations (indicated by the bright red spots) and three backup locations (indicated by the dark red spots). The images under the red spots numbered 2, 4, and 6 were linked to in my November 2019 post. The images under red spots marked by a “D” are earlier images taken by MRO when SpaceX was researching a potential Dragon landing site. The images under red spots labeled 1P and MRO are subsequent images taken by MRO since November 2019, with the 1P image previously linked to in a post in April 2020 entitled “The icy Phlegra Mountains: Mars’ future second city.”

The poster outlined why the prime candidate sites — PM1, EM16, AP1, and AP9 — were favored. For example, PM-1 in the Phlegra Mountains “…has the lowest latitude and elevation of the group, a clear association with LDAs [lobate debris aprons that resemble glacial features], well developed polygons, and has the highest SWIM [Subsurface Water Ice Mapping] score for geomorphic indicators of ice.”

EM 16 “…has a clear association with an LDA with nearby brain terrain and the strongest radar return for shallow ice and the highest combined SWIM score.”

AP1 “…appears to be the safest site and has a moderate combined SWIM score for ice.”

AP9 “…has the thickest ice from radar returns and geomorphology indicating shallow ice. It has the highest combined SWIM score for ice, but appears slightly rocky and rough.”

Below the fold are images, rotated, cropped, and reduced to post here, of the four primary landing sites, as well as links to the full images of all four plus the three back-up sites (AP8, EM15, and PM7).
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A drainage channel on Mars

A drainage channel on Mars
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Today’s cool image from Mars highlights what is probably the biggest geological conundrum the red planet presents for planetary scientists. The photo to the right, rotated, cropped, and reduced to post here, was taken on February 1, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Though I have cropped it, I have cropped out very little, because the entire meandering drainage valley is its most interesting feature, and that takes up almost the entire image.

The photo was simply labeled by the camera team a “terrain sample northwest of Sytinskaya Crater”, so I suspect this was taken not in connection with any specific research but because they must use the camera at a regular intervals to maintain its temperature, and when they have gaps in their schedule they try to pick spots of interest in areas that have not had many high resolution photos taken. In this case however I suspect the location choice was very far from random, as they clearly wanted to capture this drainage system, in its entirety.

I called this merely a drainage channel without indicating what caused the channel, be it liquid water, ice, or wind, because in this case that is a main question. At first glance an Earthman will immediately suspect water, which is what scientists supposed for the last half century. The problem with that conclusion is that the Martian atmosphere is too cold and thin for liquid water to exist on its surface, and though there seems to be plenty of evidence that liquid water once existed there, no scientist has yet come up with a completely accepted climate model that allows for such conditions in anytime in Mars’ past.

The rover Opportunity found that some channels it explored might have been carved by wind, though to our human eyes it seems unlikely that a meandering tributary system such as this could have been carved by wind. The possibility however must not be dismissed out of hand, since Mars is an alien planet and alien things (to Earth) happen there.

The overview map below might provide some context.
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Scallops of Martian ice

Scallops of Martian ice
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Cool image time! The photo to the right, cropped to post here, was yesterday’s captioned image from the MRO science team. From the caption, written by Shane Byrne of the Lunar and Planetary Lab University of Arizona,

About a third of Mars has water ice just below the dusty surface. Figuring out exactly where is vital for future human explorers. One of the ways scientists do this is to look for landforms that only occur when this buried ice is present. These scallops are one of those diagnostic landforms.

A layer of clean ice lies just below the surface in this image. As the ice ablates away in some spots the surface dust collapses into the hole that’s left. These holes grow into the scallops visible here as more and more ice is lost.

You can see those holes near the top of the scallop’s slopes.
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A cracking Martian glacier?

A cracking Martian glacier?
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Cool image time! The photo to the right, cropped to post here, was taken on December 4, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO)

I have cropped it to show at full resolution the area that contains what the scientists apparently consider the most interesting feature in this image, which they have labeled as “pits forming lines.” These are the vertical cracks and strings of holes that can be seen in this glacier-like flow. In addition, you can see that the cracking is not just vertical, but also extends out in horizontal directions, though the widest cracks are all vertical.

The next image below, which is a lower resolution crop of the full photo, shows a wider view to provide a better picture of the glacier itself.
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How the blobby craters on Mars help map the planet’s existing accessible water

Distorted blobby crater rim in Utopia Planitia
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Today’s cool image on the right, rotated, cropped, and reduced to post here, is part of a series of cool images that have repeatedly shown the blobby and squishy look of crater impact sites in the Martian northern lowland plain dubbed Utopia Planitia. Taken on January 2, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), it shows the southeast rim of a very distorted crater that appears filled with glacial material and is also surrounded by an apron of smooth material.

At 42 degrees north latitude, it is somewhat expected to find evidence of glacial-like features in such a crater. Moreover, throughout the 30 to 60 degree mid-latitude band in Utopia Planitia are found numerous such blobby craters (other examples found here, here, and here), all suggesting that the impact occurred on a flat plain with a layer of water ice close to the surface. The heat of the impact melted that ice layer. In such a circumstance, the crater rims were easily deformed because as liquid water (for a short time) it could flow into any number of shapes.

At least that’s my theory. According to Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona,

The exact processes that create the patterns are still debated. The flattened/degraded rims are not necessarily related to this morphology, as such craters can have sharp rims, so they may relate to post-impact modification.

In other words, later erosion after the crater formed could have rounded the rim and maybe even distorted it from a circle.

Regardless, the processes that made this crater rim look as it does were clearly widespread, as shown in the wider view below, provided by the context camera on MRO.
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Strange ridge ripples on the windswept plateau above Mars’ biggest canyon

Strange ridges on Mars
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Today’s cool image is once again another of what I dub a “what the heck?” photo. The picture to the right, cropped to post here, was taken on December 17, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and captures some very strange ridges on the plateau above Mars’ biggest canyon, Valles Marineris.

The image, labeled merely as a “terrain sample,” was taken not as part of any specific research project but scheduled by MRO’s science team in order to maintain the camera’s temperature. When they do this they try to take pictures covering something interesting, but often it is a potshot that sometimes shows little of interest.

In this case the photo shows something very strange. The ridges in the sample are packed into one area only, but if you look at the full image you will see that they are also scattered about randomly and sometimes isolated on the flat plains surrounding this spot.

Interestingly, these ridges resemble the first “What the heck?” image I ever posted in 2019. That photo was located at about the same elevation as these ridges, but due west in the volcanic plains near Mars’s giant volcanoes and just off the western edge of the overview map below.
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A iceberg of water ice floating on a Martian dry ice sea

Ice mesa near Mars' south pole
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British biologist John Haldane once once wrote, “The universe is not only queerer than we suppose, but queerer than we can suppose.”

Today’s cool image to the right, cropped to post here, is a fine example of Haldane’s words. It was taken on January 15, 2021 by the high resolution camera on Mars Reconnaissance Orbiter of a single lone mesalike feature sticking up in a flat expanse of Mars’ south polar dry ice/water ice cap.

I emailed Shane Byrne of the Lunar and Planetary Lab University of Arizona, who had requested the photo, to ask him what he thinks we are looking at. His response:

This region has a thick layer of CO2 ice sandwiched between water ice that’s above and below. CO2 ice is denser than water ice so I think a fragment of water ice of the underlying layer has risen up through the denser CO2 ice that covers this area (what geologists call a diapir).

Byrne also admits this remains merely “just a wild theory,” not yet confirmed.

Assuming this theory to be right, in a sense then this mesa is not really a mesa at all but an iceberg of water, floating not in a saltwater liquid ocean as on Earth but on a frozen sea of dry ice. Talk about queer! The wider shot below, taken by MRO’s context camera, illustrates how isolated this water iceberg is on that dry ice sea.
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Mars: Planet of many glaciers

Moraines on Mars
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Today’s cool image more than simply cool, it reveals a wider picture of Mars that should be quite exciting to future colonists. The photo to the right, rotated, cropped, and reduced to post here, was taken on January 30, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). What drew my attention to it was the title given to this uncaptioned photo: “Moraine-Like Ridges in Nereidum Montes.”

Moraines are the debris pile pushed ahead of any glacier. The picture shows what appear to be a series of moraines, likely caused by different periods of glacier activity when the glacier was growing. It also suggests that past active periods were more active than later ones, as with each active period the moraine did not get pushed out quite as far.

The location, Nereidum Montes, intrigued me, as I am not that familiar with it. I emailed the scientist who requested the image, Dan Berman, senior scientist at the Planetary Science Institute in Arizona, and asked him for more information. He suggested I read a very recent paper he co-wrote entitled “Ice-rich landforms of the southern mid-latitudes of Mars: A case study in Nereidum Montes.” From that paper I was able to produce the map of Mars below that shows the regions on the planet where scientists now think hold the greatest concentrations of glaciers.
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Ice-filled Martian sinkhole

Ice-filled pit on Mars
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Cool image time! The pit shown in the high resolution photo to the right (image rotated, cropped, and reduced to post here) was taken on January 25, 2021 and labeled by the Mars Reconnaissance Orbiter (MRO) “Collapse Pit in Graben with Ice Fill.”

There is a lot of information in that title. First, a graben is a geological feature where a section of terrain drops relative to the surrounding terrain, producing a depression. Second, it appears the graben in this region is mostly filled with debris, probably wind-blown dust or sand or volcanic ash.

Third, at this particular spot the filling material sank, like a sinkhole on Earth, creating the pit.

And fourth, and maybe most intriguing, the scientists think that this pit is now filled with ice. At 47 degrees north latitude, the location is prime for such ice, and the interior material resembles similar glacial features seen in many other mid-latitude craters.
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Dao Vallis: A giant river of ice on Mars

The glacier in Dao Vallis
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on December 26, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows an apparent glacial flow in a canyon heading downhill to the southwest, with evidence of a gully on its western wall whose collapse apparently squeezed into that glacial flow, pushing it to the east.

What makes this particular image interesting is not its uniqueness but just the opposite. Almost every high resolution picture along the length of this 750 mile long canyon, dubbed Dao Vallis, shows the same thing, an ice-filled ravine with that ice flowing like a river downhill.

The overview map below provides some spectacular context.
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Mining country on Mars?

The southern end of Nili Fossae

Today’s cool image might very well be giving us a glimpse of one of the most promising regions on Mars for future mining. The photo to the right, rotated, cropped, and reduced, is made up of two context camera images from Mars Reconnaissance Orbiter (MRO), found here and here. I chose to begin with this wider context camera mosaic because this is one of the rare times the context camera is more exciting an image than the close-up high resolution photo.

This photo covers the southern end of the one of the two curved fissures dubbed Nili Fossae and are thought to be left over evidence of the giant impact that created Isidis Basin to the southeast. These two fissures are about 300 miles long, and can be as much as 1,600 feet deep in places. At this southern end, we can see what look like at least two different drainage channels feeding into the fissure.

The overview map below provides the context of this location on Mars, including its relationship to Jezero Crater where Perseverance now sits.
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Cave boxwork on the Martian surface

Boxwork in Wind Cave on Earth
Boxwork inside Wind Cave, South Dakota, mere inches across.

Anyone who has ever visited either Wind or Jewel caves in South Dakota has likely seen some wonderful examples of the cave formation boxwork, formed when the material in cracks is more resistant to erosion that the surrounding bedrock, which once eroded away leaves behind the criss-crossing ridges seen in the picture to the right.

Today’s cool image provides us what appears to be an example of boxwork on Mars. However, unlike on Earth it is not in a cave but on the surface. It is also much larger. Instead of the ridges being almost paper thin and stretching for inches or feet, this Martian boxwork is feet wide with ridges extending hundreds of feet in size, as shown by today’s cool image below.
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A deep south Martian dune with bright patches

Dune with bright patches
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Cool image time! Last week the MRO science team posted a new captioned image entitled “Bright and Dark Dunes” featuring a particularly large single dune in the floor of a 25-mile-wide unnamed crater located at about 68 degrees south latitude. The photo to the right, rotated, cropped, reduced, and color enhanced to post here, shows that dune. According to the caption, written by Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona,

This image shows a large sand dune with bright patches. Martian dunes near the poles often have bright patches in the spring, when seasonal frost is lingering. However, this image is from late summer, when frost is long gone. What is going on here?

A close-up look with [MRO’s high resolution camera] provides some clues. The bright patches are made up of large ridges that look like wind-blown bedforms. Additionally, the bright patches are yellowish in the infrared-red-blue image. In enhanced color, most sand on Mars is blue but dust is yellow. This suggests that the bright bedforms are either built from, or covered by, dust or material with a different composition.

Thus, the bright patches reveal either aspect of the dune’s underlying structure, either inherent in the bedrock itself, or the texture of its surface that allows it to hold more dust. As Dundas adds, “I think more study would be needed to determine the answer in this particular case.”

There are other aspects of this dune that can be seen by a look at the wider view afforded by MRO’s context camera below.
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Skiing dry ice boulders on Mars, captured in action!

Grooves in dune created by sliding dry ice blocks
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Today’s cool image is an update on a previous cool image published in April 2020 about how scientists believe the grooves seen on the slope of a giant dune in Russell Crater on Mars are believed to be formed by frozen blocks of carbon dioxide sliding down the slope when spring arrives. The photo to the right, taken on March 3, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and rotated and cropped to post here, shows these grooves. As I wrote then,

Because the block is sublimating away, the gas acts as a lubricant so that it can slide down the hill. If large enough, the dry ice block will stop at the base of the hill to disappear in a small pit. If small enough, it actually might completely vaporize as it slides, explaining the grooves that appear to gradually fade away.

The scientists actually did a test on Earth, buying a dry ice block at a grocery store and releasing it at the top of a desert dune. Go to my April 2020 link above to see the very cool video.

Several planetary scientists did further combing through many MRO photos of this dune and now think they have spotted examples where the camera actually captured a block as it was sliding downhill.
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Searching for ice in the Martian low latitudes

Low latitude crater with intriguing debris on its floor
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Today’s cool image well illustrates the effort of planetary scientists to map out the range of buried ice on the Martian surface. Taken on December 13, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and rotated, cropped, and reduced to post here, it shows a 3.5-mile-wide crater located in the southern cratered highlands, but for those cratered highlands at the very high northern latitude of 24 degrees.

The black streaks on the crater’s interior slopes are probably slope streaks, but these are not the subject of this article. Instead, it is the material that covers the crater’s floor. These features resemble the glacial fill material that scientists have found widespread in the latitude bands between 30 to 60 degrees latitude. However, this crater is farther south, where such ice would not be stable and should have sublimated away.

Could there still be ice here? I emailed the scientist who requested the photo, Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona, and asked him what I was looking at. His answer:
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Martian pits or dark splotches?

Martian pits or dark splotches?
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Cool image time! The photo to the right, cropped to post here, was taken on January 2, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a windswept sandy region of ridges and dunes with two dark features nestled between ridges.

What are these dark patches? At the available resolution they appear to be deep pits, with the one on the right having a significant overhang. And if these are pits, they would appear significantly different than most of the previously identified Martian pits, which are usually somewhat circular in shape. These features have very complex shapes, as if the pit is conforming itself to the terrain that surrounds it.

The resolution, however, is not good enough to confirm this interpretation. These dark patches could also be exposed volcanic material, darker than the surrounding terrain. The location, as shown in the overview map below, adds weight to this interpretation.
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All systems on Perseverance so far check out good

The Perseverance science team reported this past weekend that all systems on the rover have so far reported back and are operating as expected, including the test helicopter Ingenuity.

Some more images were sent back, all visible at the Perseverance raw image website. The most spectacular new image of Perseverance released however was one taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and posted below.
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Partly ice-filled Martian crater?

Partly ice-filled Martian crater?
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Time for another cool Martian image. The photo to the right, rotated, cropped, and reduced to post here, was taken on January 3, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The section I have focused on is a single crater about a mile and a half wide.

What makes this crater interesting is the material that appears piled up against the crater’s northern half. Furthermore, both the floor of the crater as well as this piled up material looks like it is eroding away, kind of like a block of ice which is having warm water sprayed on it.

So, is this glacial ice?
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Eroded mound in Mars’ glacier country

Eroded mound in Mars' glacier country
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Cool image time! The image to the right, reduced to post here, was a captioned release today by the science team of the high resolution camera on Mars Reconnaissance Orbiter (MRO). It is located in Deuteronilus Mensae, a region of chaos terrain in the transition zone between the northern lowland plains and the southern cratered highlands that is also part of a 2,000 mile-long band that I call Mars’ glacier country. From the caption, written by Dan Berman, senior scientist at the Planetary Science Institute in Arizona:

Lobate debris aprons are commonly found surrounding dissected plateaus in the Deuteronilus Mensae region of Mars. They have been interpreted as debris-covered glaciers and radar data have shown their interiors to be composed of pure ice.

The mound in this image is slightly removed from most of the other plateaus, and the [debris apron] surrounding it is highly degraded. The sharp scarps on the western and eastern sides of the mound indicate that a great deal of the ice once found in these landforms has since sublimated away, leaving behind these collapsed debris cliffs.

I wonder if further research might find an ice layer in those cliff walls, especially because this photo strongly suggests that much of this mound is made of ice that is sublimating away or has flowed downward to form the debris aprons as well as that central gully.

The overview map below shows its location in Deuteronilus Mensae as well as showing almost all of the entire band of Mars’ glacier country.
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Enigmatic channel on Mars

Enigmatic channel on Mars
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Cool image time. The photo to the right, rotated, cropped, and reduced to post here, was taken on October 26, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and labeled by the science team as simply an “Enigmatic Channel in Syrtis Major.”

It shows a channel going downhill to the northeast east in a series of steps, separated cliffs that in the southwest hikers call pour-offs, with the channel becoming initially deeper and then slowly becoming more shallow, until the next pour-off. On Earth the pour-offs would be waterfalls, with a deep pond at the base. On Mars?

Without doubt this channel poses mysteries, but maybe with a little research we can make it less enigmatic. Asl always, the overview map below gives context, and helps give a possible explanation for what created this channel.
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Strange corroding features on Mars

Strange corroding features on Mars
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Cool image time! The photo to the right, rotated, cropped, and enhanced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 4, 2020. It shows what appears to be features that are either corroding or eroding away, with the lower areas filled with rippling sand dunes.

The circular features might be ancient craters. The material that partly fills them might be a layer of dust or sand that the wind is slowly blowing away to dig out the depressions along the southern cliff wall.

According to the MRO science team’s interpretation of the colors produced by the high resolution camera [pdf], the dark blue colors here are likely “coarser-grained materials (sand and rocks)”, while the orange-red material on the higher terrain is likely dust.

Could this material be evidence of buried ice eroding away? At first I thought so, and then I took a look at the photo’s location, as shown in the overview image below.
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New paper: Underlying ice layer seen in Martian gullies at LOW mid-latitudes

Snow on Mars?
Click to see full image.

In a paper just published, scientists are proposing that bright areas seen in the low mid-latitude gullies on Mars are the underground ice table newly exposed as surface dust is removed.

This paper is a reiteration in more detail of a previous presentation [pdf] by these same scientists at the 2019 the 50th Lunar and Planetary Science Conference in Texas and reported here in March 2019.

The image to the right, from the paper, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) in 2009, and has been cropped to post here. The white streaks are what the scientists propose is that exposed underground ice table. At 32.9 south latitude, this particular gully would be the closest to the equator that such an ice layer has been identified. All the previous ice layer discoveries have been in the ice scarps found at latitudes above 50 degrees. As the paper’s lead author, Aditya Khuller at Arizona State University, explained in to me in an email, “We believe we are seeing exposures of dusty ice that likely originated as dusty snow.” From their paper:

We suggest … that the light-toned materials are exposed H2O ice. … [T]he appearance, and then subsequent disappearance of these light-toned materials, suggests that they are some form of volatile, such as dusty ice, rather than dust alone. … [The appearance] of these light-toned materials is similar to the >100m thick, light-toned ice deposits exposed on steep mid-latitude scarps, indicating that these materials are probably also ice, with some amount of dust on, and within the ice.

The layer would have likely been laid down as snow during a time period (a long time ago) when the rotational tilt of Mars, its obliquity, was much higher than today’s 25 degrees. At that time the mid-latitudes were colder than the poles, and water was sublimating from the polar ice caps to fall as snow in the mid-latitudes.

The overview map below reveals some additional intriguing possibilities.
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Rover update: The rovers are coming! The rovers are coming!

With the imminent landing on Mars of both the American rover Perseverance only days away on February 18th followed by China’s rover in April, I think it time for a new rover update, not only providing my readers a review of the new landing sites but a look at the most recent travels of Curiosity on Mars and Yutu-2 on the Moon.

Curiosity

Curiosity's view of the base of Mount Sharp, February 12, 2021
Click for full resolution image.

Overview map of Curiosity's most recent and future travels

The panorama above, made from four images taken by Curiosity’s right navigation camera on February 12, 2021 (found here, here, here, and here), looks south to the base of Mount Sharp, now only a short distance away. The yellow lines on the overview map to the right show the area this panorama covers. The white line indicates Curiosity’s previous travels. The dotted red line in both images shows Curiosity’s planned route.

The two white dots on the overview map are the locations of the two recurring slope lineae along Curiosity’s route, with the plan to get reasonable close to the first and spend some time there studying it. These lineae are one of Mars’ most intriguing phenomenon, seasonal dark streaks that appear on slopes in the spring and fade by the fall. There are several theories attempting to explain their formation, most proposing the seepage of a brine from below ground, but none has been accepted yet with any enthusiasm.
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Inexplicable ridges in Hellas Basin on Mars

Sinuous ridge in Hellas Basin
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Time for some more cool but mysterious Martian images! The photo to the right, rotated, cropped, and reduced to post here, is the first of two images today, both of which show the ridges but of a completely different nature. Both are located in Hellas Basin in Mars southern hemisphere.

This first picture was taken on September 4, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows a sinuous complex that resembles to a remarkable extent a set of river tributaries, but is instead a set of raised ridges rather than a canyon system.

Scientists have found more than 10,000 miles of such ridges in the northern hemisphere in Arabia Terra, the most extensive transition zone between the southern highlands and the northern lowlands, and have dubbed them fossilized rivers. From a 2016 press release:

The inverted channels are similar to those found elsewhere on Mars and Earth. They are made of sand and gravel deposited by a river and when the river becomes dry, the channels are left upstanding as the surrounding material erodes. On Earth, inverted channels often occur in dry, desert environments like Oman, Egypt, or Utah, where erosion rates are low – in most other environments, the channels are worn away before they can become inverted. “The networks of inverted channels in Arabia Terra are about 30m high and up to 1–2km wide, so we think they are probably the remains of giant rivers that flowed billions of years ago. Arabia Terra was essentially one massive flood plain bordering the highlands and lowlands of Mars. We think the rivers were active 3.9–3.7 billion years ago, but gradually dried up before being rapidly buried and protected for billions of years, potentially preserving any ancient biological material that might have been present,” added Joel Davis.

Nor are such features on Mars limited to Hellas and Arabia Terra. For a particularly spectacular feature in the cratered highlands see this 2019 post.

The origin of these sinuous ridges in Hellas might have a similar origin as these other fossilized rivers. At present the bottom of Hellas, the deepest basin on Mars, is a place with little signs of ice. In the past there is evidence that lakes once existed here, so we cannot rule out water as a cause.

At the same time, Hellas was formed by a gigantic impact. One cannot dismiss the possibility of a volcanic origin, impact melt left over from the heat of that crash.

Today’s second ridge complex in Hellas looks far different.
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Another “What the heck?!” image on Mars

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Click for full image.

Today’s cool image, taken on September 2, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and cropped and reduced to post here, is one that I will make very little attempt to explain. It falls into a category I call “What the heck?!” The uncaptioned website labels this “Ringed Ridges in Kasei Valles”, which merely describes what we see.

This isn’t an impact crater. The rings don’t fit any morphology I’ve ever seen for such features.

Could we be looking at some type of glacial feature? The latitude, 29 degrees north, makes this unlikely but possible. Even so, it sure doesn’t look like it. The ripples in the center and between the ridges are sand dunes, not glacial features.

Might this be a volcanic vent, with the concentric ridges marking multiple eruptions? Maybe, but if so I’ve never seen any volcanic vent or caldera that looked quite like this.

The overview map below gives some context, but hardly explains anything.
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More weird features and changes on Mars

Some strange stuff on Mars
Click for full 2020 photo.

Overview map

Cool image time! The photo to the right, rotated, cropped, reduced, and annotated to post here, was taken on September 28, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Uncaptioned and labeled “Reticulate Bedform Change Detection on Arsia Mons West Flank,” it shows a whole bunch of strange features in addition to a change that occurred sometime in the past two years.

I think it also well illustrates in one image how alien Mars is.

The main features in this photo are what scientists have dubbed reticulate bedforms. These features, found mostly in the high elevations on the flanks of the giant volcanoes in the Tharsis Bulge to the west of Valles Marineris, are thought to be ancient dunes made of volcanic dust and debris that has solidified into an aggregate. These dunes are found with a variety of patterns.

Aggregates on the flanks are transported downslope by katabatic winds and form linear and “accordion” morphologies. Materials within the calderas and other depressions remain trapped and are subjected to multidirectional winds, forming an interlinked “honeycomb” texture. In many places on and near the volcanoes, light-toned, low thermal inertia yardangs and indurated surfaces are present.

The photo to the right appears to show all three patterns, even though it is located on the northwestern slopes of of Arsia Mons, the southernmost of the string of three giant volcanoes in the Tharsis Bulge. On the overview map to the right, this photo’s location is indicated by the white box. The black boxes indicate the location of all the pits caves that surround Arsia Mons which I have previously posted about on Behind the Black.

It is intriguing that, at least at this point, these particular reticulate bedforms on the slopes of Arsia Mons happen to be in a region where few cave pits have so far been identified. It could be that the conditions that form each are mutually exclusive. If you get pits on the slopes of Martian volcano you can’t have reticulate bedforms. Or maybe not all the pits have yet been located, or the flanks of the volcano has many more reticulate bedforms that I simply have not documented.

Either way, this particular cool image has two areas of interest, as noted by the white boxes above.
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On the edge of Mars’ giant volcanic flood plain

Flows and pitted material on the edge of Mars' great volcanic flood plain
Click for full image.

Cool image time! The photo to the right, cropped and reduced to post here, was taken on September 30, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Uncaptioned, it shows what the science team labels “Flows and pitted material in Terra Sirenum.”

Downhill is to the southeast, which means the pitted material forms some sort of filled terrain, with the surface eroded similarly everywhere. At a latitude of 32 degrees south, these flows could conceivably be glacial features. Are they?

A wider look might help answer that question. Below is a photo taken by MRO’s context camera, cropped and reduced to post here.
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