Tag: Mars Reconnaissance Orbiter

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Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 12, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The image is rotated so that south is at the top. The science team labels this a “subsidence feature,” or in plain English, a sinkhole.

Its perfectly circular shape, plus its central peak, strongly suggests we are looking at an impact crater. However, the lack of a raised rim of debris, produced by the ejecta from the impact, raises questions about this conclusion, and is one reason why the scientists think this is a sinkhole instead. Its shape however could be telling us that this sink is simply mirroring the existence of a buried crater.

The overview map below as always provides more context.
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Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 4, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The MRO science team labeled this simply “Diverse Terrain,” an apt description but woefully incomplete.

Though the grade here goes uphill to the south, there are ups and downs along the way. The flat areas near the top as well that band near the bottom appear to be the oldest terrain, with the rough hollows appearing to be places where that flat material has sublimated or eroded away.

This terrain is in the very high southern latitudes. South is to the bottom of this picture, with the south pole of Mars about 380 miles away. Thus, that eroding top layer is likely disappearing because it has either water ice or dry ice within it, and over time it sublimates away.

The picture itself was taken in winter, when the entire surface is likely covered with a thin mantle of dry ice that fell as snow with the coming of colder temperatures. A wider view of this region in the spring, taken by MRO’s context camera, shows that this mantle, now appearing like white frost, appears largely confined to the higher terrain. Apparently, the annual sublimation of this dry ice mantle is linked somehow to the erosion of this flat terrain.

The additional location information provided by overview map below helps explain why this terrain is so diverse.
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Cool image time! The photo to the right, cropped, reduced, and sharpened to post here, was taken on September 10, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what appears to be a relatively featureless plain with a surface resembling stucco.

At -9 degrees south latitude, this is in the Martian dry equatorial regions. No ice or glaciers here. However, the consistent orientation of the knobs and hills suggest dunes and sand blown by prevailing winds, and that guess holds some truth. This location is deep within the Medusae Fossae Formation, the largest volcanic ash deposit on Mars, covering an area about as big as India, and believed to be the source of most of the red planet’s dust.

We are thus looking at thick layer of ash, its surface shaped over eons by the winds of Mars’ thin atmosphere.
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Cool image time! The photo to the right, cropped, reduced, and sharpened to post here, was taken on August 31, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists call “layering” surrounding this pointed mesa, which I roughly estimate to be somewhere between 200 to 400 feet high.

As you approach the mesa you first walk on the dust-covered flat plains. Then you start up a slope of what looks like alluvial fill, material that over time has fallen from the mesa to pile up as an apron at its base. You then reach a series of terraces, each likely marking a different layering major event from sometime in the distance past. Over time, for unknown reasons, the material surrounding this material has eroded away, while the mesa and its layers somehow survived.

The overview map below helps tell us what those past layering events were, as well as the source of the large amount of dust and sand at this location.
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Cool image time! The photo to the right, cropped, reduced, and sharpened to post here, was taken on July 14, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the dune filled floor of an unnamed 25-mile-wide ancient and very eroded Martian crater.

These endless dunes — which extend far beyond this photo to cover the entire floor of this crater as well as an overlapping crater to the north that is only slightly smaller — reveal something fundamental about this location: The winds prevail from one direction consistently, from either the north or the south. Closer inspection would likely resolve which way, but I don’t have the knowledge or access to the data to do so.

The overview map below, provides context, and also further information about why these dunes are here.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 28, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). While it shows what looks like a somewhat typical Martian glacial flow pushing through a gap between hills, this glacial flow is not typical. It sits at just under 30 degrees north latitude, closer to the equator than almost any glacial feature on Mars. Moreover, the younger impact crater on top suggests this glacier has been here for some time. Though the impact is younger than the crater, it is not that young, as the dark streaks normally seen in the first years after impact are gone.

Thus, this glacier suggests that not only can near surface Martian ice exist closer than 30 degrees latitude from the equator, it can survive there for a considerable amount of time.

Nor is this glacial flow, so close to the equator, unusual for this region of Mars.
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Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on August 21, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as a “layered mound.” It also shows a plethora of geological mysteries, all of which relate to the as yet not quite understood geological history of Mars.

First, note the different colors north and south of the ridgeline. According to the science team’s understanding of what these colors mean [pdf], the orange-red to the north suggests dust, while the bluish-green to the south suggests coarser materials, such as rocks and sand. Though frost and ice are generally bluer, such things are generally found on the pole-facing slopes where there is less sunlight. Thus the bluish-green material to the south is unlikely to be ice or frost, though this is not impossible, as the picture was taken in the winter and the latitude is 35 degrees north.

Why however is there such a dichotomy of rocks, sand, and dust between the north and south slopes? And if frost and ice, why is it more prominent to the south, when it should instead be more prominent to the north?

Other mysteries: Is the circular depression on the ridgetop an impact crater or a caldera? If the latter, this suggests the mound is some kind of volcano, likely mud, though lava is not excluded. If so, however, why is there no caldera on top of the ridge to the south?

The location, as shown in the overview map below, reveals other puzzles.
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Cool image time! The photo to the right, cropped, reduced, and enhanced to post here, was taken on August 26, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Though the science team labels this image vaguely as showing “Features in Mamers Valles,” the features are likely glacial ice since this location is at the western end of the 2,000-mile-long northern mid-latitude strip I dub glacier country, where glacial features are seen everywhere.

The white dot marks this picture’s location in Mamers Valles, as shown on the overview map above. This particular Martian channel, that meanders in a wildly random manner (including a few sharp ninety degree turns), is theorized [pdf] by some scientists to have formed not by surface flows but by a subterranean drainage that created voids. On the surface the voids caused sagging, collapses, and the eventual formation of the surface channel.

Under such conditions, any ice in the channel would not necessarily have a clear flow direction, thus providing an explanation (though hardly certain) of the eddy-like shape of these features.

Cool image time! The photo to the right, rotated, cropped, reduced, and enhanced to post here, was taken on September 2, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team titled this picture “Gullies with Terminal Ridges on Glacial Crater Fill,” a title that in one phrase encapsulates everything we see here of this unnamed 8-mile-wide crater’s western rim and interior.

The crater is located at 46 degrees south latitude inside the much larger 145-mile-wide Kepler Crater, and about 1,500 miles east of Hellas Basin in a region where a lot of glacial ice is found. A context camera image taken in July 2020 shows the entire crater floor apparently covered with glacial fill that on the edges appears to be eroding away.

Today’s high resolution photo focused on the western part of the crater, where that eroding edge was instead replaced by a meandering ridge reminiscent of a moraine. The gullies on the interior slope to the west, as well as the parallel north-south cracks, suggest that debris falling and sliding down from that rim had pushed up against this glacial ice and created that ridge.

There is a lot more to this geology however.
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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! The photo to the right, rotated, cropped, and reduced to post here, should at first glance be one of my “What the heck!?” images. However, a little detective work quickly provides us some understanding of the inexplicable geology seen at this particular location on Mars.

The picture was taken on August 29, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and was labeled by the science team a “Lobate Debris Apron in Deuteronilus Mensae.” This mensae region is the western part of the 2,000-mile-long strip in the northern mid-latitudes of Mars that I label glacier country, since almost every high resolution picture taken in this strip shows extensive glacial features.

This picture is no different, showing what appears to be glaciers, but by itself it is still difficult to make sense of it. Glaciers flow downhill, like rivers. In this high resolution image the direction of flow is somewhat unclear.

As always, a wider view clarifies the picture.
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Cool image to end the week! The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken by on July 18, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the bedrock layers on one of two very large mesas that jut out into the floor of 108-mile-wide Terby Crater.

I want to focus your eye on the spoon-shaped mesa near the top right of the photo. Note how the layers can be seen on both sides, even though the top of the mesa seems to be concave. This is strange and complex geology, made even more fascinating in that the two mesas almost reach the center of the crater floor. Why are they here? Why were they not flattened during impact, like the rest of the crater floor? Or maybe the original crater floor is the mesa top, but if so, why did the rest of the crater interior get eroded away.

The overview map below provides some context, and helps fill in some details, even if it fails to answer any of these questions.
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