Tag: geology

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Cool image time! The picture to the right, rotated, cropped, and reduced to post here, was taken on April 18, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows only one of many flat-topped mesas in a chaos terrain region dubbed Oxia Chaos.

The mesa top is about 540 feet above the floor of the canyon to the north, which in turn is about 840 feet below the flat terrain north of it. That flat terrain to the north is not part of the chaos terrain, however, but the northern rim of the plateau that surrounds the chaos. Moreover, this particular piece of rim is separating from the plateau, as shown near the top of this January 16, 2008 context camera image from MRO. At some point in the future it will break off and fall into that canyon and on top of this mesa.
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Cool image time! The picture to the right, cropped and reduced to post here, was taken on April 30, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the rim of a seventeen-mile wide crater, and was the scientists label a “gully without apron,” meaning that though something has caused material to disappear within that gully, beginning high on the rim wall, there does not appear to be any piled up apron or debris at the gully’s base.

The blue colors imply the possibility of frost within the gully, while the orange suggests dust or coarse surface material.

The cracks emanating away at right angles from the gully’s base suggest glacial ice, which makes sense based on the location.
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In looking through new images from Mars Reconnaissance Orbiter (MRO), I sometimes stumble some very strange things, with today’s cool image an example. The picture to the right, rotated, cropped, and reduced to post here, was taken on May 7, 2023 by MRO’s high resolution camera, and shows the western half of a two-mile-wide crater with a very weird rim, almost as if a person had decided he wanted to reshape it with a filigree pattern.

Though only two-miles wide, this crater actually has been named Johnstown. I suspect this is because of its strange rim, prompting a research effort and the need to provide it a name. Why the rim has this repeating pattern of gaps, however, is beyond my pay grade to explain, and I have been unable to track down any research papers about it. The nearby surrounding surface suggests vaguely the possibility that this is a caldera, not an impact crater, but even so why would the rim of the caldera have these regular breaks?
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Today’s cool image takes us to one of Mars’ biggest canyon systems that while linked to Valles Marineris, the biggest Martian canyon of them all, is considered a separate canyon system because it is made up of a labyrinth of criss-crossing canyons instead of a single major canyon line.

In fact, its name is Noctis Labyrinthus, as shown on the overview map to the right. In many ways its complex pattern is reminiscent of the chaos terrain seen mostly in Mars’ mid-latitudes, but there are major differences. The rectangle marks the area we shall zoom into below to show these differences as well as to feebly illustrate the grand scale of these canyons.

First, the formation of these canyons is closely linked to the volcanic events that formed the three giant volcanoes to the west. They are also strongly linked (in ways not yet fully understood) with the suspected catastrophic floods that drained from Noctis, through Valles Marineris, and out into the northern lowland plains to the east, eons ago when this dry equatorial region could have been wet.
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Today’s cool image once again illustrates that the things that orbiters photograph on the Martian surface are not always what they seem at first glance. The picture to the right, cropped, reduced, and sharpened to post here, was taken on March 23, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as “layering” in this small mile-wide crater.

That layering, seen on both the interior and exterior slopes of its circular rim, is what makes this crater puzzling. It suggests this crater was not formed by an impact, but by volcanism. The layers suggest repeated eruptive events. That the crater sits above the surround plain by about 100 feet strengthens this conclusion.

And yet, a look at the overview map below suggests this conclusion is premature.
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Cool image time! The picture to the right, rotated, cropped, reduced, sharpened, and annotated to post here, was taken on April 8, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The picture shows a terrain of swirls and terraced mesas. Because the shadows are deceptive, I have annotated the picture to show the actual drainage pattern of those swirls, suggesting that whatever material forms these swirls is not only draining about 200-250 feet down into the low point at the picture’s center, the swirls are also draining toward the small 1,000-foot-wide crater in the upper left. That crater however appears to lie on top of the swirls, which means it came after them.

What are the swirls made of?
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on April 16, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows in the center an ancient tongue of lava flow that is surrounded by thick dust fields on the north and the south.

The arrow indicates the downhill grade. It also shows the direction of the prevailing winds, downhill to sculpt the volcanic ash into long streamers of parallel grooves, with obvious eddies forming around bits of older lava that still stick up through the ash. On the lava flow can also be seen one small volcano cone, on the picture’s right edge, suggesting that either during this flow or after it hardened magma bubbled up from below.

The location is fascinating, and in fact puts this picture into its much more spectacular context.
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Cool image time! The picture above, rotated, reduced, and brightened slightly to post here, was taken on April 13, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It cuts a swath across an eleven-mile-wide crater only about 500 miles from the edge of Mars’ north pole ice cap.

The overview map to the right marks its location, as indicated by the white dot on the right edge of the map. The inset shows the soft and likely icy nature of the surface in which this impact occurred. The crater resulted in a secondary outside ripple, that quickly hardened after impact.

The image was taken during spring, shortly after the sun’s light hit this crater. The cracks in the ice indicate long term sublimation that is slowly reducing the amount of water ice inside the crater. Like mud cracks in the desert after a puddle has evaporated, the ice here is cracking to produce polygon fractures.

It is also very likely that everything here is coated with a thin mantle of clear dry ice, deposited as snow from the atmosphere in the winter and then sublimating away with the coming of spring. That spring dry ice sublimation is likely ongoing, and this picture is probably an attempt by scientists to detect that process.

Why the surface colors shift from aquablue to orange might have to do with that sublimation process, or it might be revealing areas covered with dust (orange). That the northern parts of the strip is blue and the southern parts orange suggests the former. Or not. I don’t have enough information to answer this question with any confidence.

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Cool image time. The picture to the right, cropped to post here, was taken on March 14, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Dubbed simply a “terrain sample,” this image was likely taken not as part of any specific research project, but to fill a gap in the camera’s schedule in order to maintain its temperature by taking regular images. When the camera team needs to do this, they try to find interesting locations not previously photographed. Sometimes the photos turn out somewhat boring. Most of the time however they capture something very intriguing.

In this case, the intriguing feature of this picture is its stippled surface that seems to overlay a relatively flat surface underneath, with some faint covered craters visible. On top are several more recent craters that suggest either the impact landed in very soft material, thus producing little ejecta and no crater rims or the craters are not craters but sinks, places where the ground is subsiding due to some underground process.
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Cool image time! Today’s cool image begins with the overview map to the right. The white dot marks its location, on the western edge of Amazonis Planitia and about 1,000 miles east of the giant shield volcano Elysium Mons.

This is a region of numerous flood lava events that appear to cover the knobby mountainous terrain that was once here. We know that past terrain was knobby because in the black outline just south of this picture the knobs are everywhere, short peaks sticking up from a very flat flood lava plain. The region is also on the northern edge of the dry equatorial regions of Mars, at 27 degrees north latitude. It is likely there is little near surface ice here.

These details will help explain the cool image itself.
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Cool image time! The picture to the right, rotated, cropped, and reduced to post here, was taken on March 25, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labeled this image “Cross-Section of Glacier-Like Form,” probably because the mesa in the center of the picture clearly shows numerous layers as you descend from its peak to the surrounding plains, an elevation difference of about 200 feet.

The white dot about 250 miles due south of Lyot Crater on the overview map above marks the location of this mesa, inside the chaos terrain of Deuteronilus Mensae that is the western section of the 2,000 long strip in the northern mid-latitudes of Mars that I call glacier country, since practically every image, like today’s, suggests the presence of glaciers.

The oblique mosaic below, created using MRO’s context camera images, illustrates this fact even more spectacularly.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on April 28, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Dubbed a “terrain sample” by the camera team, it was likely taken not as part of any specific research project but to fill a gap in the camera’s schedule so as to maintain that camera’s proper temperature. When they have to do this, they try to pick interesting targets, though there is no guarantee the result will be very interesting.

In this case the camera snapped what appears to be a drainage channel between two deeper hollows. The channel sits about 100 feet above the western hollow and 260 feet above the eastern hollow. This makes some sense, as the overall drainage in this region is going from the west to the east, and then to the north.
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Cool image time! The picture to the right, enhanced, cropped, reduced, and sharpened to post here, was taken on April 1, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labels as “Rough Ground and Bright Exposures” on the flanks of a wide mountain range on Mars, whose highest point is about 4,400 feet higher to the northeast and about 30 miles away.

The arrow indicates the downhill grade. Notice the smooth flat areas that seem to only partially cover much rougher terrain below. To my eye this top layer resembles an Earth glacier that has partly sublimated or melted away, exposing the rougher bedrock below that has been ground and scraped by the glacier previously.

However, this is not on Earth, so assuming it is like an Earth glacier is dangerous.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on February 15, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labeled this a “Terrain Sample”, which suggests but doesn’t guarantee that it was to fill a gap in the camera’s schedule in order to maintain that camera’s proper temperature, and therefore was targeted at a relatively random but potentially interesting location.

What we see is a fissure canyon, about 250 to 300 feet deep with cliffs about 125 high, that appears surrounded and even filled with icelike features. Even the craters on the plateau above the canyon appear like they either impacted in ice, or have since been filled and eroded by that ice.

But is it ice?
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