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
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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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The freaky floor of Mars’ Hellas Basin

The perplexing floor of Hellas Basin
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Today’s cool image takes us to the Death Valley of Mars, Hellas Basin, a place I like to call the basement of Mars. The photo to the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on September 28, 2020, and gives us another example of the very strange and inexplicable geological formations that are often found on the floor of Hellas.

The picture was taken not as part of any particular research project, but somewhat randomly for engineering reasons. In order to maintain the proper temperature of MRO’s high resolution camera, it must take images in a regular cadence. When large gaps in time occur between requested images, the camera team then picks locations to fill those gaps, sometimes randomly, sometimes based on a quick review of earlier wide angle images.

Sometimes these “terrain sample” images are quite uninteresting. More often they hold baffling surprises.

I think the photo to the right falls into the latter category. Though the terrain covered by the full image is largely flat and lacking in large features, the surface is strewn with perplexing small details.

The light streaks might be dust devil tracks, but why are they light here when such tracks are routinely dark everywhere else on Mars? What formed the many parallel small ridges? What caused the smooth solid patch near the photo’s center top? And why do the ridgelines at the western edge of that patch run in almost a perpendicular direction to the other ridges?

All a mystery, but then the floor of Hellas Basin is filled with such mysteries. Below is a list of some other cool images of the floor of Hellas, all weird and mystifying. Also below is an overview elevation map of Hellas Basin, with darker blue indicating the lowest elevations. The white cross marks the location of today’s photo.
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Back to Mars’ glacier country

Tongue-shaped glacial flow on Mars
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The cool image to the right, rotated, cropped, and reduced to post here, was taken on November 3, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labels a “Possible Tongue-Shaped Flow Feature in Protonilus Mensae.” There is no caption, so I will try to provide.

Protonilus Mensae is part of the long string of chaos terrain that runs about 2,000 miles along the transition zone between the southern cratered highlands and the northern lowland plains at about 30 to 40 degrees north latitude, and includes the other mensae regions dubbed Deuteronilus to the west and Nilosyrtis to the east. This region of Mars I like to call glacier country, because almost every high resolution photograph appears to show glacial features. To get an idea what I mean, take a gander at these past posts, their locations indicated by number in the overview map of Protonilus Mensae below:
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The strange moated mesas of the Kasei Valley on Mars

Overview map

In showing my readers today’s cool image, I want to present it as it is seen by scientists, first from a far distance that with time increasingly zooms in to reveal mysteries on a very human scale.

The overview map to the right essentially gives us the view of Mars as seen by scientists following the Mariner 9 orbiter mission that began mapping the Martian surface in late 1971 after the conclusion of a global dust storm that had hidden its surface initially. As the first high resolution map of Mars, the orbiter revealed numerous puzzling and surprising features, including the largest volcanoes and canyons in the solar system. The orbiter also found that the red planet’s surface was comprised of two very different regions, the northern lowland plains and the southern cratered highlands.

The overview map, covering from about 13 degrees south latitude to about 34 degrees north latitude, shows us all but the southern cratered highlands. The white box in Kasei Valles is where today’s cool image is located. Both Kasai and Valles Marineris represent those giant canyons, all invoking to Earth eyes the possibility of catastrophic floods of liquid water sometime in the past.

Ascraeus Mons is the northernmost of the three giant volcanoes east of the biggest volcano of all, Olympus Mons. All sit on what scientists now call the Tharsis Bulge.

Chryse Planitia, where Viking-1 landed in 1976, is part of those northern lowlands that some scientists believe might have been once had an intermittent ocean sometime in the past. Today’s image is about 600 miles from the outlet into Chryse Planitia.

The geological mystery of all these features demands a closer look, something that scientists have been pursuing now for more than a half century.
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The pit caves of Mars: Can humans someday live in them?

Four more pits in the Tharsis Bulge on Mars

It has been more than four months since my last report on the pits of Mars. Time to do another.

The collage to the right shows the four different pits photographed by the high resolution camera of Mars Reconnaissance Orbiter (MRO) since October. The links to each image are:

Like almost all the cave pits so far found on Mars, all are in the Tharsis Bulge of giant volcanoes to west of Valles Marineris. The overview map below shows these pits in the context of every other pit in this region that I have featured on Behind the Black.
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The slowly disappearing dry ice cap at Mars’ south pole

The Happy Face crater near Mars' south pole
Click for the 2020 full image.

Cool image time! The photo to the right of two images taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) was posted as a captioned image by the orbiter’s science team today.

This crater, dubbed the Happy Face Crater because of the shape of the blobby features within it, is located on the south pole ice cap of Mars, about 200 miles from the south pole itself.

Today’s caption noted how these pictures, taken nine years apart, illustrate the change going on at the Martian south pole.

The “blobby” features in the polar cap are due to the sun sublimating away the carbon dioxide into these round patterns. You can see how nine years of this thermal erosion have made the “mouth” of the face larger. The “nose” consisted of a two circular depressions in 2011, and in 2020, those two depressions have grown larger and merged.

While this caption noted the importance of studying these long term changes in order to understand the evolution of Mars’ climate and geology, it did not give the very specific discovery these changes suggest for Mars globally, a discovery that is actually very significant.

The two ice caps of Mars have some fundamental differences, all presently unexplained. The similarities are obvious. Both have permanent caps of water ice that are presently believed to be in a steady state, not shrinking or growing. Both each winter get covered by a thin mantle of dry ice that sublimates away completely with the coming of spring.

The differences are more puzzling, as shown by the maps of the two poles below.
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Mysterious colors on Mars, near the landing site of Europe’s rover

Mysterious colors on Mars
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Cool image time! Today the science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) released a new captioned image, which I have cropped and reduced to post here to the right.

The photo was taken October 12, 2020, and shows a small very colorful area on top of an isolated hill. To quote the caption, written by Sharon Wilson:

An isolated, elongated mound (about 1 mile wide and 3.75 miles long) rises above the smooth, surrounding plains. Horizontal layers are exposed at the northern end of the mound, and its surface is characterized by a very unusual quasi-circular pattern with varying colors that likely reflect diverse mineral compositions.

…The origin of this mound is unknown, but its formation may be related to the clay-bearing rocks in the nearby Oxia Planum region.

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Craters in slush on Mars

Dust devil steak across a slushy plain on Mars
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on October 27, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It was taken not for any particular research project, but as one of the periodic images the camera team needs to take maintain the camera’s proper temperature. When they need to do this, they often will take a picture in an area not previously viewed at high resolution. Sometimes the image is boring. Sometimes they photograph some geology that is really fascinating, and begs for some young scientist to devote some effort to studying it.

In this case the photo was of the generally featureless northern lowland plains. What the image shows us is a scattering of impact craters that appear to have cut into a flat plain likely saturated with ice very close to the surface.

How can I conclude so confidently that these craters impacted into ice close to the surface? The location gives it away.
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The colorful and bright knobs of Ariadnes Colles on Mars

Colorful and bright knob in Ariadnes Colles
Click for full image.

Today’s cool image gives us a sample of the strange colorful hills in an even stranger knobby depression on Mars called Ariadnes Colles. The photo to the right, cropped and color enhanced to post here, was taken on September 10, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It focuses on just one of those colorful hills. The color strip only covers the western half, which is why that is the only part of the hill in color.

Ariadnes Colles is a patch of chaotic terrain 110 by 100 miles in size, located in the southern cratered highlands due south of Mars’s volcano country, at latitude 34 degrees south. What makes this particular patch of chaos distinct from the many others on Mars is that the hills, knobs, and mesas within it are routinely bright and colorful, compared to the darker surrounding terrain. Moreover, as noted in this Mars Express press release for images of Ariadnes Colles from that orbiter,

In contrast to other chaotic terrains … Adrianes Colles is not a water-source region. It is still debated, therefore, whether Ariadnes Colles was formed by the action of water or wind.

The darker material in the southern areas is most likely sand or volcanic ash; some slopes of the flat-topped features have been covered by this dark material that was blown up on the slopes.

The sand or volcanic ash most likely come from the Medusae Fossae Formation several hundred miles to the north, the largest volcanic ash deposit on Mars. The colors on the hill likely come from a variety of minerals.

The overview map below shows the entire patch, with the location of the hill above indicated by the white dot in the red rectangle that shows the full image location.
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Partly engulfed Martian craters

An engulfed crater on Mars
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 31, 2020. It shows a crater that appears buried in a sea of material so that pretty much the only thing visible is top of its rim.

The full image shows a second larger crater to the northwest that looks the same. In both cases the material fills the craters also fills the surrounding terrain.

Yet, both craters appear to be surrounded by a faint skirt of uplifted material.

What caused this situation?
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Draping moraines on Mars

Draping moraines on Mars
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Cool image time! The photo on the right, rotated, cropped, reduced, and annotated to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on October 6, 2020. It shows the northern interior rim of 42-mile-wide Greg Crater in the southern cratered highlands of Mars.

What makes it interesting is the curving ridge that appears to drape itself around several larger hilltops. That ridge is a moraine, the debris or glacial till that accumulates at the foot of glaciers as push their way down hill. As the glacier had flowed those hills became obstacles, so that the glacier (and its moraine) were forced to go around.

The overview map and wider view from the context camera on MRO below give the setting.
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A glacier filled canyon on Mars?

Large glacial flow exiting Mamers Valles
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The photo to the right, rotated, cropped, and reduced to post here, was taken on September 9, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the northern half of a 15-mile wide canyon on Mars whose floor appears to be completely filled by a glacier. The full picture shows both the north and south rims, and captures the canyon’s outlet from the southern cratered highlands into the chaotic terrain of Deuteronilus Mensae, the region of Mars I like to call glacier country. This region of canyons and mesas forms the transition zone down to the northern lowland plains, and is a region where almost every MRO image shows glacial-type features.

The size and age of this glacial feature is what makes it stand out. First, note the craters on its surface. The glacier has to be quite old and inactive for a long time for those craters to still exist as they appear. Any movement would have distorted them, and they show little distortion.

The overview map below gives a sense of this glacier’s size.
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A Martian “glacier” made of volcanic ash

A Martian
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Of the numerous cool images I’ve posted on Mars, many have documented the growing evidence that in the mid-latitudes of the Red Planet are many buried glaciers of ice.

Today’s cool image to the right, rotated, cropped and reduced to post here, shows something that at first might resemble the features one would expect from an ice glacier, but in reality is actually a flow of volcanic ash being blown almost like a river, with the prevailing winds blowing from the south to the north.

The photo was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on November 1, 2020. The location, very close to the equator and in the transition zone dubbed the Cerberus Plains, is also smack dab between Mars’s biggest volcanoes, a region I like to dub Mars’s volcano country. The overview map below gives the context.
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Summer at the Martian south pole

Overview of the Martian south pole

Today we have two cool images, both giving us a tiny glimpse at what it is like in the middle of summer on the fringes of Mars’ south pole ice cap. Their location is indicated by the blue crosses on the overview map on the right.

To review, the south pole on Mars is, like its north pole, mostly made up of a permanent icecap of water. In the south, this icecap is mostly mixed with dust and debris in the area outlined in black and dubbed the layered deposits. On top of this is a smaller thick water ice cap, indicated by light blue, which is in turn topped by a thin cap of frozen carbon dioxide, or dry ice, indicated by white. During the winter the entire pole, down to 60 degrees latitude also gets covered by a temporary mantle of dry ice, that sublimates away each spring.

Now for our cool images!
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Striped dunes in crater on Mars

Striped dunes in crater on Mars
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Cool image time! The photo on the right, rotated, cropped, and color-enhanced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 1, 2020. It shows some large dunes with what appear to be black or dark features across their surface, reminiscent of tiger stripes.

The dunes are located on the floor of 42-mile-wide Kunowsky Crater, located in the northern lowland plains of Mars at the high mid-latitude of 57 degrees north.

What are the tiger stripes? The second image below, provided at the image link, zooms in at full resolution at the area in the white box, and shows that the stripes appear to actually be made up of spots strung together.
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A Martian polliwog

Three-mile-wide crater with exit breach
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on September 30, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

It shows one half of what scientists have dubbed a pollywog crater, in which there is a single breach in the crater wall, aligned with the low point in the crater’s floor. Such craters suggest that they were once water- or ice-filled, and that they drained out through the breach either quickly in a single event or slowly over multiple events.

The second image below was taken by the wide angle context camera on MRO, and not only shows this entire crater, but several other adjacent craters, all of which show evidence of glacial fill in their interiors. The latitude here is 34 degrees south, placing these craters within the mid-latitude bands where such glacial features have been found by scientists in great numbers.
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Terraced mesas in Martian crater

Terraced mesa in Martian crater
Click for full resolution image.

The cool image to the right, reduced and annotated to post here, was a captioned photo released by the Mars Reconnaissance Orbiter (MRO) science team earlier this week. Taken by MRO’s high resolution camera, it shows in color a beautifully stair-stepped mesa located in an unnamed 22-mile-wide equatorial crater in Arabia Terra, the large transitional zone between the lowland northern plains and the southern cratered highlands. As the caption notes,

Several craters in Arabia Terra are filled with layered rock, often exposed in rounded mounds. The bright layers are roughly the same thickness, giving a stair-step appearance. The process that formed these sedimentary rocks is not yet well understood. They could have formed from sand or volcanic ash that was blown into the crater, or in water if the crater hosted a lake.

If volcanic ash, the layers are signalling a series of equal eruptions of equal duration, which seems unlikely. Water is also puzzling because of the equatorial location. Like yesterday’s mystery cool image, water is only likely here at a time when the red planet’s rotational tilt, its obliquity, was much higher, placing this at a higher latitude than it is today.

Regardless, make sure you look at the full image here. This crater floor is chock-full of more such terraced mesas, some of which are even more striking than the sample above.

I have also posted below the MRO context camera photo of the entire crater.
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A splat on Mars

A splat on Mars
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Cool image time! The photo to the right, cropped to post here, was taken on October 31, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labelled simply as a “Terrain Sample”, it was not taken as part of any specific science research but because the MRO science team need to regularly take pictures to maintain the camera’s temperature. When such engineering images are required they try to pick spots of some interest, but sometimes the resulting picture is somewhat bland.

If you look at the full image, you will see that blandness generally describes it. However, in the upper left corner was a most intriguing-looking crater, which I have focused on above. From all appearances, when this impact happened the ground was quite soft, almost like mud, and thus the ejecta splattered away not as individual rocks and debris but as a flow.

The map below gives a little context, but really doesn’t explain this crater fully.
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Cones on Mars!

Today’s cool image is actually a bunch, all found recently in the monthly image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO).

All the photos I post below show pimple-like cones, all of which appear to be a type of small volcano. The cones are found in a wide range of locations, from the northern lowland plains to the cratered highlands to the mid-latitude transition zone between the two. They are also found at the bottom of deep canyons, in the floors of craters, and amidst mountains.

Let us begin.
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