Tag: geology

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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 6, 2021, and shows a mid-latitude crater in the northern lowland plains of Mars with what appear to be layered glacial features filling its interior.

The theory that scientists presently favor for explaining many of the features we see on Mars is based on many climate cycles caused by the wide swings the planet routinely experiences in its obliquity, or rotational tilt. When that tilt is high, more than 45 degrees, the mid-latitudes are colder than the poles, and water ice sublimates southward to those mid-latitudes to fall as snow and cause active glaciers to form. When that obliquity is low, less than 20 degrees, the mid-latitudes are warmer than the poles and that ice then migrates back north.

Such cycles, which are believed to have occurred many thousands of times in the last few million years, will place many layers on the ground in both the mid-latitudes and at the poles. The layers in this crater hint at this.

The overview map below gives some further context.
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on February 2, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and was labeled as “Exhumed Craters Exhibiting Concentric Fill”.

The term “Concentric Fill” is used by planetary scientists to mark glacial-type features frequently found inside craters at latitudes greater than 30 degrees latitude. This crater however is at 22 degrees north latitude, too close normally to the equator to expect a buried glacier inside it. Any ice at such a latitude is expected to be underground and well protected. A debris covered glacier would likely sublimate away, which I think is why the scientists labeled this “exhumed.” Though there are the concentric features near its inside rim as well as covered by the sand dunes on the crater’s floor, they are assuming this is only evidence of past ice, no longer there. This assumption is strengthened by the splattered but eroded nature of the surrounding terrain. Such splats are typical of high latitude impacts in regions with ample buried ice. The eroded nature of this splat however suggests it is very old and has likely lost its ice.

Then again, this is an assumption.
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Every spring for the last seven Martian years scientists have eagerly aimed the high resolution camera on Mars Reconnaissance Orbiter (MRO) at the steep 1,500 to 3,000 foot high scarp at the edge of northern polar ice cap in order to capture images of what is Mars’s most spectacular annual event, the occurrence of tens of thousands springtime avalanches along that scarp.

Well, spring has returned to the northern hemisphere on Mars, and the scientists have begun another monitoring campaign. The photo to the right, cropped to post here, was taken on March 7, 2021 by MRO. It shows a particularly dramatic part of that scarp, a place where the scarp separates two curved alcoves and is thus narrowed down to a ridge about 1,000 feet high.

The nose of the ridge is sloping downward to the northwest, so the horizontal bands on its crest are actually evidence of older and older layers exposed as the elevation drops. The blue and black markings on the left slope are likely evidence of this season’s first avalanches, or might even be avalanches occurring as the picture was snapped! As explained to me by Shane Byrne of the Lunar and Planetary Lab University of Arizona during the last Martian avalanche season,

On Mars half of the images we take in the right season contain an avalanche. There’s one image that has four avalanches going off simultaneously at different parts of the scarp. There must be hundreds to thousands of these events each day.”

The overview map below shows the location of this picture, as well as all the other places the scientists have routinely monitored in the fourteen-plus Earth years since MRO reached Mars orbit.
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Today’s cool image to the right, rotated, cropped, and reduced to post here, was taken in January 2012 by the context camera of Mars Reconnaissance Orbiter (MRO). The location is a small section of the Tartarus mountain range that is cut by the Cerberus Fossae fissures, all located in Elysium Planitia, the large volcanic lava plain that lies between Mars’ big volcanoes. The white cross on the overview map below marks the location of the photo.

I picked this photo because it quickly shows us in one picture many of the typical features one finds in that lava plain.

For example, the distinct fissure that cuts across the mountains near the top of the picture is the northernmost large fissure of Cerberus Fossae. In my initial post on Cerberus I mistaken thought its large and many hundreds of miles-long fissures might be evidence of underground lava tubes. Since then I have learned while the depressions may signal underground voids, they are not a lava tubes but graben, cracks formed by the movement of the terrain on each side. The cracks opened when past volcanic activity caused the ground to swell upward, stretching and splitting it.

The dark splotch in the flat area just south of the fissure remains me of the maculae found in these lava plains to the west of Olympus Mons, splotches that for still undetermined reasons dust devils like to congregate, blowing off the red dust so that the dark basalt lava becomes visible. No high resolution image of this spot has yet been taken, so this is a pure guess on my part.

The mountains near the bottom of the photo illustrate the ancient lava flood that inundated these mountain peaks. The white box shows the area covered by the recent MRO high resolution image that I include below.
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on November 29, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled simply as “periglacial survey,” it is one of almost two hundred such images taken by MRO over the years, almost all of which are in the high latitudes above 60 degrees, with most being in the southern hemisphere. Most appear to be close to or above Mars’s Arctic Circle, which means these are locations that will see little or no sunlight for a portion of the year.

I have been unable to contact the scientists doing this survey, so I will have to make an educated guess as to its purpose and goals. “Periglacial” refers to the outer fringes or margin of a glacier or large ice sheet. Thus, in the context of this survey, the scientists appear to be studying places where they think the Martian high latitude ice sheets are beginning to sublimate away. Today’s photo is a good example. It is located at 67 degrees south latitude, in the southern cratered highlands but in an area that appears to be relatively free of craters. Instead, the terrain appears somewhat flat with only periodic depressions and scarps. The MRO context camera photo below of the same area, rotated, cropped, and expanded to post here, illustrates this.
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Cool image time! The photo to the right, rotated and cropped to post here and taken on January 15, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), shows the colorful top of a small mesa in the northern lowland plains of Mars and about 300 miles north of the planned landing zone for Europe’s Franklin rover, scheduled to launch in 2022.

What makes this mesa stand out is the bright and colorful areas on its slopes. The colors are false, but they indicate [pdf] certain things. The yellow is likely dust covered rock. The pinkish rock is also likely dust-covered, but made up of coarser material. The bluish strip running along the mesa’s northern slope is possibly frost or ice, not unlikely as this mound is at 25 degrees north latitude and was taken during winter. The slope faces north, which would put it in shadow much of the time during winter.

The colors however only hint at what is there.
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Today’s cool image focuses on one of the weirdest flow features I have yet seen on Mars. The first photo to the right, rotated and cropped to post here, comes from a January 27, 2021 picture by the high resolution camera on Mars Reconnaissance Orbiter (MRO). This cropped section focuses on the middle of three such weird features, two close flows heading downhill on the interior rim of very eroded 28-mile-wide crater. For some reason the flows also have depressions on their crowns. The depressions almost look like someone carved them out with a spackling spatula. In fact, the MRO science team agrees, labeling this image as “Spatulate Depressions with and without Upslope Gullies.”

The second image to the right shows a wider crop of the same picture, and explains the reason for the last half of that label.
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Cool image time! In the March 1st image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO) were two pictures covering sections of the interior rim of 40-mile-wide Renaudot Crater, located in the northern lowland plains of Mars north of the region I dub Mars’ glacier country.

The map to the right provides the context. The two red boxes in Renaudot Crater show the location of the two images below, with the first being the one to the left. Located at about 42 degrees north latitude, we should expect to see evidence of ice and glacial features here, and that is exactly what both photos show.
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Today’s cool image is one of my “what the heck?” photos. The picture to the right, cropped and reduced to post here and taken on September 3, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), shows a strange dune field of many parallel long dunes, cross-cut by larger ridges.

Are the larger ridges dunes? Or are they some form of volcanic or tectonic ridge, which is also very typical of this region, called Tempe Terra and located in the transition zone between the southern cratered highlands and the northern lowland plains?

Or are they eskers, ridges frequently found in places that were once covered by glaciers? At 35 degrees north latitude, it would not be surprising to see glacial features here, but as far as I can tell, the full image has no obvious such features.
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Cool image time! The photo to the right, cropped and reduced to post here and taken on January 7, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), provides us a perfect example of the kind of glacial feature that scientists find routinely in the 30 to 60 degree mid-latitude bands on Mars. In this case the crater is in the northern reaches of a chaos region dubbed Nilosyrtis Mensae, the easternmost mensae region of what I dub glacier country on Mars.

When first identified scientists named this concentric crater fill, a purposely vague term that is only descriptive because they then did not know what it was made of, though they had their suspicions that it was buried glacial ice. Since then radar data has routinely confirmed that there is ice in such filled craters, making this particular glacial feature one of the most prevalent in those mid-latitude bands.

You can see a quite similar ice-filled crater, also in Nilosyrtis, in an earlier post from October 2020. While that earlier crater was on the southern edge of Nilosyrtis, today’s crater is about 300 miles almost due north, near the region’s northern fringe. In between are lots of similar glacial features, sometimes in craters, sometimes flowing off the slopes of mesas, and sometimes flow features in the open canyons between.

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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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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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