Tag: Mars Reconnaissance Orbiter

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Cool image time! The image to the right, cropped and reduced to post here, was taken by Mars Reconnaissance Orbiter (MRO) on May 1, 2020, and shows a truly intriguing crater that they dub a “Crater Hanging on Mesa Wall.”

Located in Deuteronilus Mensae, a chaos region of mesas and cross-crossing canyons in the transition zone between the northern lowland plains and the southern cratered highlands, the crater literally overhangs the edge of this canyon’s cliff. The overview map to the right, with this location indicated by the red box, illustrates what this region’s geology is like.

The most likely explanation is that the impact occurred prior to the creation of the canyon, and when the canyon eroded, the material in and of this crater was more resistant, probably because the impact had packed it together to increase its density.

At the same time, the features inside both craters in the photo, as well as below them on the floor of the canyon, suggest the presence of buried glaciers, something not unlikely at the 45 degree north latitude where this crater sits.

So, here’s a guess at the geological history. First we had the impact, then during the eons of glacial ebb and flow on Mars due to wide swings in the planet’s obliquity (its rotational tilt), the canyon was cut, with that erosion leaving the crater sitting high above the canyon floor below it.

One more curious detail: The material in the canyon seems asymmetric, suggesting that the crater actually dips down toward the canyon, as if it as a unit has tilted to the east as the canyon was worn out below it.

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Cool image time! The photo to the right, cropped and reduced to post here, was taken on April 30, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Uncaptioned, the science team titled the release as a “Cataract in Osuga Valles.”

To understand what we are looking at it is necessary to also see a wider view, as provided by the context map below and to the right. As you can see, this image straddles across the canyon called Osuga Valles, and heads downstream to the east. It also shows a point where the grade of that canyon suddenly drops. If water ever flowed here this place would have been the location of a truly spectacular waterfall.

More likely, these cataracts mark the location where sometime in the past a glacier had flowed down this valley, cutting a path until it broke out into the large and wide dead end area that appears to have no clear outlet. For some reason at this point the downhill grade of this canyon suddenly dropped, with the glacier following that sudden steep drop.

There is no glaciers here now, as this location is at 14 degrees south latitude, too close to the equator for any ice to remain close to the surface. Instead, dust dunes remain as the only feature flowing down through these cataracts.

The second overview map provides further context, showing the location of Osuga Valles relative to nearby Valles Marineris, the largest known canyon system in the solar system. Whatever process formed that gigantic canyon system certainly was a factor in forming Osuga Valles. The details however are not yet understood with any certainty. All we presently have are theories.

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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 18, 2020. It shows a very strange central peak in a crater on Mars. Not only does this peak stick out like a sore thumb in a relatively flat crater floor, its surface is strangely textured, patterned with what look like scallops.

The overview map below shows the area covered in the crater by the full image.

My guess is that the peak is the final impact melt from the original impact. Think of a pebble thrown into a pond. You get ripples (the crater rim) as well as an upward drop of water (the central peak). Unlike pond water, the material in a crater freezes quickly, leaving both the ripple and the upward drop frozen in place.

This peak however also reminds me of volcanic cones found in the American southwest, the remnant cone of a much larger volcano that has long ago eroded away.

The textures might be evidence of that erosion process, as they resemble scallops that wind and water erosion can cause on rock faces.

We also could be seeing dunes on the slopes themselves, though I think this is unlikely. This crater is on the edge of the vast Medusae Fossae Formation, the largest volcanic ash deposit field on Mars, as shown by the white cross on the overview map below. Thus, being on the edge of this ash field there is a lot of available dust and sand that can pile up on these slopes.

Still, the sunlight side of the ridge suggests the scallops are in bedrock, not sand dunes. And to assign their origin to either wind or water or ice erosion I think is a stretch.

So while the peak is probably the frozen melt remains of the original impact, the scallops are a geological mystery that needs unraveling.

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Cool image time! The science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) today released a cool captioned image entitled “Exquisite Layering”, showing a place on the floor of Holden Crater where the dust and sand that normally covers most of the Martian surface has been wiped away, cleared off because these layers are on higher sloping terrain.

The image to the right, cropped to post here, focuses in on that exposed layering, believed to be sedimentary and must have therefore happened in the eons following the impact that caused the crater.

The overview map to the right shows with the red box the location of this layering inside Holden Crater. The map also illustrates why this crater was considered a candidate landing site for Curiosity. Like Gale Crater, it has evidence — the large meandering canyon system flowing into the crater — that suggests it had once been filled with a water lake. These sedimentary layers support that hypothesis, suggesting that this lake was intermittent. Each time it refilled and then dried up, it laid down a new deposit of those sedimentary layers.

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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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Cool image time! The photo to the right, cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on March 2, 2020, and shows some inexplicable shallow pits and depressions in the middle of a relatively flat and featureless plain.

Make sure you click on the image to see the full photo. Though the plain looks remarkably smooth, a handful of dark splotches are scattered about, almost all of which occur on top of small craters.

What causes these depressions? The MRO team calls this “Landforms near Cerberus Tholi.” Cereberus Tholi is a a collection of several indistinct and relatively small humps that scientists think might be shield volcanoes.

More clues come from the overall 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! The science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) yesterday released a new captioned image, entitled “Disrupted Sediments in Acidalia Planitia”, noting that the photo

…shows a pitted, blocky surface, but also more unusually, it has contorted, irregular features.

Although there are impact craters in this area, some of the features … are too irregular to be relic impact craters or river channels. One possibility is that sedimentary layers have been warped from below to create these patterns. The freezing and thawing of subsurface ice is a mechanism that could have caused this.

The image to the right, rotated, cropped, and reduced to post here, shows the lower quarter of the full image. While in some areas it does appear as if changes below the surface caused the surface to warp and collapse, as suggested by the caption, in other places it looks more like the top layers themselves sublimated away without disturbing what was below them.

Note for example the pits near the bottom of the photograph. They clearly show sedimentary layers on their cliff walls, including the tiny circular mesa in the middle of the rightmost pit.

If these pits were collapsing from below, their cliffs would be more disturbed, because it would have been those lower layers that sublimated first. Instead, it appears that the top layer disappeared first, followed by each lower layer, one by one.

This region of strange terrain is located in the middle of the northern lowland plains. The overview map below gives some context, with the small white box showing this photo’s location.
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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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The science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) today released a very cool pair of images, taken a Martian year apart, showing some significant changes that had occurred during that time in a large sand dune slope inside a crater. On the right is that pair, reduced and with the top image slightly lightened to bring out the features. As they wrote in the caption,

One large gully in particular has had major changes in every Martian winter since [MRO’s high resolution camera] began monitoring, triggered by the seasonal dry ice frost that accumulates each year.

This time there was an especially large change, depositing a huge mass of sand. The sand divided into many small toes near its end, or perhaps many individual flows descended near the same spot. Additionally, a long sinuous ridge of sand was deposited. This could be a “levee” that formed along one side of a flow, but there is not much sand past the end of the ridge, so it might also be the main body of a flow.

Nor is this dune gully the only active one in this crater, dubbed Matara Crater, located in the southern cratered highlands at about 50 degrees south latitude. If you look at the full image and compare it with an image from 2009 there are many changes across the entire slope field that extends a considerable distance to the north and south of the cropped section shown above.

At this latitude atmospheric carbon dioxide settles as frost during the winter, then sublimates away with the coming of spring. The freeze-sublimation process disturbs the sand each year, causing these avalanches.