Tag: geology

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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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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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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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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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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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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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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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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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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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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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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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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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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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