Tag: geology

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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on February 17, 2012 by the wide-view context camera on Mars Reconnaissance Orbiter (MRO). It shows a section of the northern lowland plains of Mars, latitude 31 degrees north, where several very inexplicable and isolated ridges can be seen.

One ridge meanders mostly in a north-south direction, while a second instead meanders east-west. The shape of both says that neither has anything to do with any past impact crater. In fact, their random snakelike shape doesn’t really fit any obvious explanation. For example, they do not fit the look of the many fossil rivers found on Mars, where the hardened and dry riverbed channel resists erosion and becomes a ridge when the surrounding terrain erodes away.

What geological process caused them? In the decade since this photo was taken the scientists who use MRO have only been able to snap a handful of high resolution images of these ridges. The image below is the most recent, covering the area in the white rectangle above.
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on January 2, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Simply labeled “slope features,” it was likely taken to monitor the gullies and streaks on the interior walls of this 4-mile-wide crater. Scientists have been using MRO to track the coming and going of frost on this crater’s interior walls since 2016.

Equally intriguing however are what appear to be squashed layers within the crater’s interior. These appear to be some form of glacial feature created by repeated climate cycles, similar to the glacial features routinely seen throughout the 30 to 60 degree mid-latitude strips north and south.

What makes the glacial features in this particular crater particularly intriguing is its location, as shown in the overview map below.
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Cool image time! The photo above, rotated, cropped, and reduced to post here, was taken on March 5, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as a “viscous flow feature,” which is another way of saying the flow was thick and syrupy.

Nor is such a flow unusual in this area of Mars. It is located in a region of chaos terrain dubbed Protonilus Mensae, which is also the central mensae region in the 2,000-mile-long strip in the northern mid-latitudes of Mars I label glacier country. The overview map above of Protonilus Mensae — covering about 500 miles in width — shows how common such flows are in this place. The black rectangles mark the locations of other cool images I have featured, as follows:

• 1. Buried glaciers flowing off of Martian mesa
• 2. Brain Terrain on Mars
• 3. How to spot a glacier on Mars
• 4. Glacier country on Mars
• 5. Revisiting Mars’ glacier country
• 6. Back to Mars’ glacier country
• 7. A cracking Martian glacier?
• 8. Ice-filled craters in Mars’ glacier country?

The red rectangle indicates the location of today’s cool image.

The glacial aspect of everything in this region is even more emphasized by the wider view provided by MRO’s context camera below.
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on November 22, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labeled a sinuous ridge. Make sure you also look at the full image. The ridge goes on to the south, but then fades way as an almost perfect ramp, only to have another even more wiggly but thinner north-south ridge begin only a few feet to the west.

Sinuous ridges like this are found in many places on Mars. Almost always their origin is thought the result of a former river channel that became a ridge when the surrounding softer material eroded away.

That explanation however does not seem to work for this ridge. It has too many other inexplicable features. For example, note how the peak of the ridge smoothly transitions from sharp to flat-topped. It has a soft appearance that is strengthened by the gap near the top.

It is almost as if this ridge is a kind of elongated sand dune! And guess what: The overview map below gives that explanation some believability.
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In our third Martian cool image of the day, we go to the north pole of Mars, as seen from orbit by the high resolution camera of Mars Reconnaissance Orbiter (MRO). Taken on March 30, 2022 and cropped and reduced to post here, this picture shows some of the distinct and unique geological features found only on the polar caps of Mars. From the caption by Candy Hansen of the Planetary Science Institute in Tucson, Arizona:

Both water and dry ice have a major role in sculpting Mars’ surface at high latitudes. Water ice frozen in the soil splits the ground into polygons. Erosion of the channels forming the boundaries of the polygons by dry ice sublimating in the spring adds plenty of twists and turns to them.

Spring activity is visible as the layer of translucent dry ice coating the surface develops vents that allow gas to escape. The gas carries along fine particles of material from the surface further eroding the channels. The particles drop to the surface in dark fan-shaped deposits. Sometimes the dark particles sink into the dry ice, leaving bright marks where the fans were originally deposited. Often the vent closes, then opens again, so we see two or more fans originating from the same spot but oriented in different directions as the wind changes.

The top layer of translucent dry ice falls as dry ice snow during the winter, than sublimates away with the arrival of spring. Since this photo was taken in autumn, we are looking at features left over from the activity from the spring and summer.