Search Results for: pedestal crater

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Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on August 13, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It is another fine example of the wind-blown sculpted terrain that one finds routinely in Mars’ largest volcanic ash field, dubbed the Medusae Fossae Formation. About the size of India, this gigantic field is thought to be the source of most of the dust on Mars.

This particular location sits on the northernmost edge of that huge field. The elongated mesas mark the field’s edge, disappearing to the north but becoming thick and extensive to the south. The prevailing southeast-to-northwest winds have acted to clean most of the ash away.

We can get an idea about how deep and pervasive that field once was at this location by the pedestal crater in the middle right. Once, the floor of that crater was below the top of the ash field. At that time, the top of the dunes marked the general ground level across this entire image. Over time, the winds blew most of this material away, but the denser packed floor of the crater resisted that erosion, and thus now stands above the surrounding terrain.

The more normal-looking craters nearby could have occurred before the ash was deposited, or after it was blown away. The impact that created the pedestal crater however occurred when the ash covered everything here.
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Cool image time! On Mars it is not unusual to see what scientists call tadpole features, craters with meandering canyons or channels either flowing into or out from the crater’s rim. The photo to the right, rotated, cropped, and reduced to post here, is another example, though with one major difference. The channel and crater are inverted, with the channel instead a ridge and the crater a circular plateau. The picture itself was taken on April 16, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

Orbital images have found on Mars a lot of what scientists call pedestal craters, where the impact packed and hardened the ground under the crater so that when the surrounding terrain eroded away the crater remained, as a plateau.

Scientists have also found on Mars a lot of what they call “inverted channels,” places where the channels of a drainage pattern followed the same geological process, becoming more resistant to erosion so that over time it turned from a channel to a ridge.

Here we have a combination of both. The overview map below provides us the larger picture.
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on February 2, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and shows a mesa sticking up on the relatively flat and featureless northern lowland plains in Utopia Planitia, the second largest impact basin on Mars.

The full image shows three such mesas. Though pictures taken in the northern lowlands of Utopia tend to show evidence of buried ice or glaciers, the impression I get from this picture is one of dryness. If there is any ice here, it is below ground. And even that seems unlikely. The surface surrounding nearby craters does not have that squishy and slushy look that is seen in the north when an impact occurred on near surface ice. Instead, the ground looks solid.

The overview map below reinforces this impression.
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Cool image time! Rather than talk about shut downs, lying politicians, and our tragically fear-filled society, let’s go exploring on Mars. The image to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on February 8, 2020. Dubbed a “Flow-Like Feature within the Adamas Labyrinthus”, it shows what appears to be a very distorted and eroded pedestal crater surrounded by strange triangular-shaped flow features.

It also shows, as does much other research, that the northern mid-latitudes of Mars have a lot of frozen water, much of it buried very close to the surface.

Assuming this is a pedestal crater (which it might not be), this feature has to be very old. Pedestal craters require age, as to stand out above the surrounding terrain a lot of time is needed to erode that terrain away. This age is confirmed by the bunch of newer craters on top.

At the same time, the partially filled small crater near its bottom, as well as the soft eroded depressions on top, suggest that much of this surface has been reshaped by more recent flows, changing its shape over time.

The surrounding triangular flows probably occurred at the original impact, and suggest that there is ice near the surface, making the material here act almost like wet mud when heated. Since this location is right in the middle of the mid-latitude bands where scientists have found lots of evidence of buried glaciers and ice near the surface, this supposition seems reasonable.

The overall location provides some further context.
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As a break from Wuhan flu madness I give you another cool image, cropped and reduced to post here, taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I call this stucco on Mars because that is exactly what it looks like. It is as someone laid down a layer of damp concrete and then ran over it roughly with a trowel to raise the knobs scattered across the surface.

The uncaptioned MRO image calls this “Aligned Mounds with Broad Summit Pits”. Those aligned mounds run across the top of the image. I suspect they are pedestal craters, left over because the impact had packed and hardened the crater so that it resisted erosion as the surrounding terrain was worn away.

The two insets, posted below at full resolutoin, focus on one of those pedestal craters as well as the distinct mesa at the bottom of the photo.
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Cool image time! I came across this strange feature shown on the right in my normal rummaging through the archive of the high resolution camera on Mars Reconnaissance Orbiter (MRO). The photo, rotated, cropped, and reduced to post here, focuses on what they label a “cratered cone.”

The immediate thought is that this is a volcano cone, and the craters at its peak are not impact craters but calderas. In science however such a knee-jerk conclusion is always dangerous. For example, this might instead be a pedestal crater, where the surrounding terrain was worn away over eons, leaving the crater sitting high and dry.

It is therefore important to look deeper to determine what origin of this feature might be.

First, its location, as shown in the overview map below, provides us our first clue.
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Cool image time! The photo on the right, cropped and reduced to post here, is a perfect example of the difficulty of explaining the alien landscapes on Mars, based on orbital imagery. It was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on January 23, 2020.

In this one image alone we have the following strange features, all within an area about 8 by 11 miles in size:

• Several small very obvious pedestal craters (near the top right), some located inside depressions. Pedestal craters are created because the surrounding terrain eroded away around them. Since these are pedestals, however, why are they also inside depressions?
• Two large circular mesas that appear to vaguely have terraced erosion. These might also be pedestal craters, but maybe not. They also sit much higher than the pedestal craters above. Either way, the mesas remained while the terrain around them eroded away.
• Several normal craters with a series of circular features within each. At this latitude, 34 degrees south, it is possible these craters are filled with buried ice, what scientists call concentric crater filled glaciers.
• A light-colored string of ridges aligned to almost look like a kite with tail. The light color says this ridge is not made up of the same material as the circular mesas and pedestal craters, but it too was not eroded away.
• A number of small bean-shaped depressions (just south of the biggest circular mesa and near the top left). Don’t ask me what caused them. I have no idea.

The spot is located in the Martian southern cratered highlands, as shown by the blue cross in the overview map to the right. Complicating its geological history is that it sits inside a very gigantic very old and degraded crater, with numerous newer smaller impacts overlaid on top. Any explanation needs to include these impacts, and the ejecta from them.

If you click on the image and study the full resolution photograph, you can find even more enigmatic features. For most there is a reasonable geological theory. Putting them all in one place and somehow getting all those different explanations to fit together however is far more difficult.

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Cool image time! The photo on the right, cropped and reduced to post here, shows a cluster of really strange mesas, craters, and pits, located in Utopia Planitia, the largest and deepest plain of Mars’ northern lowlands where an intermittent ocean might have once existed.

The image was taken on October 26, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) as part of its regular image-taking program. In this case it was dubbed a “terrain sample” image, meaning that it was not specifically requested by any researcher, but was taken because they need to use the camera regularly to maintain its temperature, and thus sometime produce images over previously untouched areas, not knowing what they will find, as part of that maintenance schedule.

In this case the terrain sampled is especially intriguing. Are the upraised depressions what are called pedestal craters, created when the impact landed on what was once an icy plain, which subsequently sublimated away to leave the crater sitting high above the surrounding flats? Maybe, but this location is at 23 degrees north latitude, and research has generally found these pedestal craters at latitudes higher than 30 degrees.

Moreover, that many of these upraised depressions are not circular suggests that their formation was not impact related.

Other mysteries: Why are all the ridgelines bright? What caused the parallel white streaks to the east and west of some mesas? And if these are impact craters, why are some distorted?

If this region was once the seabed of an intermittent ocean, this fact might explain the features. Then again, it is more likely that this lowland area was once covered in ice in the far past, when the planet’s tilt was greater and the lower latitudes were actually colder than the polar regions, and thus allowed ice to build up in those lower latitudes. We might therefore be seeing the end result of an erosion/sublimation process as that ice disappeared when Mars’ inclination shifted.

Lots of questions, and no answers.