Tag: Mars Reconnaissance Orbiter

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Today’s cool image returns us to the chaos region dubbed Protonilus Mensae, the middle of three adjacent mensae regions in the northern hemisphere that I like to dub Mars’ glacier country because there is so much evidence of buried ice there.

The photo to the right, cropped to post here, was taken on May 31, 2021 by the high resolution camera of Mars Reconnaissance Orbiter (MRO). Titled “Layered Feature in Crater in Protonilus Mensae,” the section I have posted focuses on several craters, with the one with the central mesa likely the picture’s target. Based on many similar features found in craters in this region, it is somewhat safe to assume that this mesa is made of buried ice.

The overview map below as always provides the context.
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Click for higher resolution. Original images found here and here.

Today’s cool image to the right is a mosaic I have made from two images taken by the context camera on Mars Reconnaissance Orbiter (MRO), showing a most intriguing region on Mars dubbed Avernus Cavi, located in the large volcanic plain called Elysium Planitia between the giant volcanoes Elysium Mons and Olympus Mons, a region I like to call Mars’ volcano country.

The mosaic shows in one picture much of the typical terrain in Avernus Cavi. We see many linear depressions or cracks, created when the ground stretched and cracked at weak points. We also see many depressions that suggest sinkholes, places where the surface sagged down because of a void below ground.

The area of knobs and mesas in the picture’s southeast quadrant is very typical Martian chaos terrain, the later result of long term erosion of these cracks and depressions.

The white box shows the area covered by the image below.
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on May 27, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows the clash of different layers on the western slope of a mountain within Mars’ largest canyon, Valles Marineris.

The scientist have labeled this a “possible angular unconformity.” In geology an unconformity generally refers to a gap in a series of layers, a period when instead of the layers being deposited they are being eroded away, leaving no record for that time period. An angular unconformity adds tilting to the older layers, which after erosion are then covered by new layers that are oriented somewhat differently.

Based on these definitions, what the scientists suspect is that the brighter layers to the left and lower down the mountain are older. After a period of erosion new layers were deposited on top at a different angle, forming the stripe of layers going from center left up to center right.

The swirly nature of the material on the top of the ridge suggests to me that these layers might be volcanic in nature, but that’s a pure uneducated guess. What some scientists do believe (but have not yet conclusively proven) is that the lower older layers are sediments laid down by an ancient lake that once filled the canyon here.

The overview map below provides a wider view and some context.
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Cool image time! The photo to the right, rotated and cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on April 27, 2021. It shows a strange scattering of dunes on a flat plain. The red at the top of each dune probably indicates exposed dust and sand. The white fringe is likely either water frost or the leftover mantle of dry ice that is deposited in the polar regions each winter down to 60 degrees latitude, and disappears with the coming of spring, sublimating back into carbon dioxide gas.

There are a lot of puzzles here. The overview map below provides some context, but only some.
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Cool image time! The photo to the right, cropped and reduced to post here, is actually a somewhat old image from the high resolution camera on Mars Reconnaissance Orbiter (MRO). It was taken more than a decade ago, on December 28, 2010, and featured as a captioned image one month later. I post it now because it was recently featured as MRO’s picture of the day, and thought it deserved a new look. As the caption from 2010, written by planetary scientist Alfred McEwen, noted,

Remember those paisley shirts during the summer of love in 1967? If so, this terrain may look somewhat familiar.

How did this terrain really form? One theory is that it’s a landslide deposit, perhaps associated with draining an ancient lake.

The overview map below might help make sense of this theory.
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Cool image time! The photo to the right, rotated, cropped and reduced to post here, was taken on April 18, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a nice sample of the typical glacial-filled craters found often in the mid-latitudes between 30 to 60 degree latitudes, surrounded by a lot of erosion features representative of these lowland northern plains.

The biggest crater is very symptomatic of what scientists have dubbed concentric crater fill, a feature that they believe reveals that there is buried ice water glaciers here, protected by a thin layer of debris. The apron of brighter material surrounding the crater could be a splash feature created during impact and now more obvious because it has been revealed as sublimation and erosion lowered the terrain nearby.

The location is north of the Cydonia region in Acidalia Planitia, several thousand miles to the northeast of the region where Viking 1 landed in 1976 and Mars Pathfinder landed in 1997, as shown in the overview map below.
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Today’s cool image, to the right, takes us to the equatorial regions of Mars, a region that today appears quite arid and dry based on all the orbital and rover/lander data so far gathered. The photo and its complex geology however provides us a hint that once liquid water did exist here. At least, that is the hypothesis that scientists presently favor, though making it fit this complex geology is not simple or straightforward.

The mosaic to the right is made from four context camera images taken by Mars Reconnaissance Orbiter (MRO). It shows a very complicated series of depressions — one of which vaguely resembles a crater — that appear to have been washed out by some past erosion process, though that process could not have been that simple because of the fissures and cracks that dominate the floor of the circular feature.

I contacted Chris Okubo of the U.S. Geological Survey, who had requested a high resolution image from MRO of a small part of this mosaic, as indicated by the white box, to ask him what we are looking at. His answer was appropriately noncommittal:
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on April 19, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Requested by Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona, the image was entitled “Enigmatic Terrain in Elysium Planitia.” The image is labeled so because, as Dundas explained,

Flood lava is a key part of the feature, best seen at the north and south ends of the image. What’s unusual is the knobby terrain at the center. … I haven’t yet been able to do a more thorough study of these features, so plenty of puzzles remain!

The higher material in the upper right is likely flood lava. A 2016 paper [pdf] led by Dundas on similar features in Elysium Planitia that were not as knobby found their origin somewhat baffling. The evidence suggested that lava, mud, wind, and ice could all be involved in their formation, but the evidence was also not sufficient to eliminate any possibility.

In the case of today’s image, the explanation might also be any of these possibilities. For example, we might be looking at the erosion of the flood lava, exposing harder knobs of different material that had been there before and had been covered by the lava. Or maybe the knobs are simply the last bits of that layer of flood lava that has not yet eroded away.

As always, the overview map provides some context.
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on March 4, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows an eroded mound that appears to have flows coming off its north and south slopes that fill the surrounding low spots, including half-covering a nearby crater.

The science team for MRO’s high resolution camera chose this picture as their April 28th picture of the day, noting the following:

The objective of this observation is to examine a crater which seems to be in the process of getting covered by flow from a mound. This image, in Protonilus Mensae, may show us characteristics of the covering material: could it be debris-covered glaciers?

Below is a global map of Mars, with this mound’s location in Protonilus Mensae in the northern mid-latitudes indicated by a black cross.
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Today’s cool image to the right, cropped and reduced to post here, is of a crater in the mid-latitudes of Mars’s cratered southern highlands. The picture was taken on January 4, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and is actually the only high resolution image ever taken of this crater.

The gullies in the north interior wall of this crater are the reason why this picture was snapped. These gullies are very typical on the pole-facing slopes of mid-latitude Martian craters, and have puzzled scientists since they were first discovered in the late 1990s in images taken by Mars Global Surveyor. Since then, thousands have been found, almost all of which in the 30 to 60 degree mid-latitude bands where glacial features are also found. Most occur on the more shadowed pole-facing interior slopes of the craters, though at higher latitudes they are also found facing the equator.

Since their discovery scientists have puzzled over their cause, which because of their locations favoring colder temperatures suggest some form of seasonal weather factor. The most preferred hypotheses propose some interaction with water ice or dry ice, or are simply dry flows of rocky granular material. None of these hypotheses have been confirmed. Some evidence suggests they are dry flows, no water involved. Other evidence points to the influence of an underground layer of water ice.

The mystery of these gullies is enhanced by by the wider view from MRO’s context camera below, rotated and cropped to post here.
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on April 1, 2021 by the high resolution camera of Mars Reconnaissance Orbiter (MRO). It shows the central portion of the floor of an unnamed 5-mile-wide crater in northeast corner of Hellas Basin, the deepest large depression on Mars.

The latitude is 33 degrees south, where many glacier features have been identified, especially inside craters.

In this case, the cracked and flaked surface of this crater floor suggests what geologists call exfoliation, “the breaking off of thin concentric shells, sheets, scales, plates, and so on.” On Earth exfoliation generally refers to an erosion process seen on rock faces, though you can see it on other types of materials.

In this Martian crater we appear to be seeing the exfoliation of different ice layers, sublimating away at different rates as they are exposed to the Sun. The layers probably suggest different periods on Mars when snow was falling here, causing the glaciers to grow. The sublimation we see now suggest periods when this region was warmer and the ice was shrinking. Whether we are in such a period now is not yet determined by scientists.

Either way, the photo suggests at least two such cycles, though if we could drill down into this material we would likely find evidence of many more.

Below the fold is a global map of Mars, showing the location of this crater with a red cross in Hellas. The regions surrounded by white borders are areas where many glacial features have been found.
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For original images click here and here.

Today’s cool image provides us a glimpse at the carved canyons created when the mid-latitude glaciers on Mars were active in the past and slowly flowing downhill into the section of the northern lowland plains dubbed Acidalia Planitia.

The photo to the right is a mosaic of two images taken by the context camera on Mars Reconnaissance Orbiter and rotated, cropped, and reduced to post here. The mosaic shows a region at the very edge of Acidalia Planitia at latitude 43 degrees north.

Below is a close-up of the area in the white box, taken by MRO’s high resolution camera on February 28, 2021, as well as a global map marking the location of this image at the very edge of the glacier country found in the chaos terrain of Deuteronilus Mensae.
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