Tag: geology

Click for original image.

Today’s cool image to the right demonstrates that the atmosphere and climate of Mars is truly different in different places. The picture, rotated, cropped, reduced, and sharpened to post here, was taken on July 22, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled simply as a “terrain sample”, it 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 proper temperature.

I post it today almost to illustrate the difference between this location and the spot where the lander Insight landed on Mars. Earlier this week the MRO camera team released a short movie created by images of the lander taken over six years, showing how the dust around it had changed over time. I noted further how those images showed a very small number of dust devil tracks, which explained why no dust devil every crossed over the lander’s solar panels to clean them of dust.

For the picture on the right, however, there are a lot of dust devil tracks, so many near the bottom that they almost completely darken the ground.
» Read more

Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on July 17, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled merely as a “terrain sample,” it 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 proper temperature.

When the camera team does this, they try to pick interesting targets. In this case, they targeted this 400-foot-high pointy-topped hill. The smoothness of its slopes suggest this hill is made up largely of packed dust, possibly a hardened former dune. This hypothesis seems strengthened by the erosion on the eastern slopes, which appears to be areas where that packed sand has worn or blow away.

Think of sandstone in the American southwest. It is made of sand that has hardened into rock, but wind and water and friction can easily break it back into dust particles, resulting often in the spectacular and weird geological shapes that make the southwest so enticing.

But is this sand?
» Read more

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 25, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the camera team labels as a “mound in the southern highlands.”

The mound in question sits in the center of the sunken depression, and at the highest resolution shows its top to be cracked and broken, as if something is attempting to break out by pushing up from below.

Everything about this picture screams near-surface ice. The cracked mound suggests ice sublimating into gas, which applies pressure to the surface and thus the cracks. The depression suggest that much of the near-surface ice at this location has already disappeared, causing the ground to sag. All the craters lack upraised rims. If caused by impacts, the ground here was soft enough that the impactor simply sank into the ground. Imagine dropping a rock you’ve heated into snow. It would simply leave a hole.

But there’s more. The white dot in the overview map above marks the location. In the inset, the lighter area surrounding this depression resembles an ice sheet that is slowly sublimating away. There are also other similar depressions in that lighter area. The lighter area also has fewer craters than the darker regions nearby, suggesting that this ice sheet covers the older impacts.

The location is in the southern cratered highlands in a mid-latitude region where many images indicate the existence of layers of ice deep below ground. This picture is more evidence of the same, but it also indicates the presence of ice very close to the surface as well.

The orbital data continues to tell us that Mars is not a dry desert like the Sahara, but an icy desert like Antarctica. There will be plenty of water for future colonists. All they will have to do is stick a shovel in the ground, dig it up, and process it.

Cool image time! The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken on July 16, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what MRO’s camera team labels as “layers near ridge in Argyre Planitia.”

The layers are strange because there is so little topographic difference between them. Though the ground slopes downward from the south to the north, dropping about 1,300 feet, it does so almost smoothly. The layers show relatively little topographic relief.

And what caused the circular shape? Is it evidence of a buried crater? And if so, why so little relief at its rim?

As always, the overview map provides some answers.
» Read more

Today’s cool image will be unlike most cool images, in that we will begin not with the image but with the overview map to the right. The long meandering canyon at the center of this map is Nirgal Vallis, a 300-mile long canyon on Mars that eventually drains to the east into a much larger drainage system that runs south-to-north several thousand miles into the Martian northern lowland plains.

At first glance Nirgal Vallis invokes a river system. It starts in the west as several branches that combine to form a single major canyon meandering eastward until it enters that south-to-north system. To our Earth eyes, this canyon suggests it was carved by water flowing eastward, the many drainage routes combining as they flowed downhill.

Today’s the cool image, its location indicated by the white dot, tells us however that liquid water might not have been what created this canyon.
» Read more

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on October 2, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The white dot in the overview map above marks the location, inside the chaos terrain of Deuternilus Mensae and part of the 2,000-mile-long mid-latitude Martian strip I label “glacier country,” because practically every image of every part of its landscape has glacial features. For example, the splash apron around the picture’s largest crater as well as the material within it all suggest some form of glacial activity and near-surface ice.

The scientists label what they see here as “Mesas in Small Craters.” These features are located in a low flat plain that geologists think was created when the ground eroded away, leaving behind scattered high plateaus that indicate the previous surface elevation. The geological map [pdf] of this plain describes it as follows:

Smooth, relatively featureless materials with regions of variable albedo north of continuous cratered highlands; exhibits scattered clusters of small circular to irregular knobs.

Based on the many accumulated photos from MRO, the general conclusion is that we are looking at a sheet of ice/dirt and covered by a thin dust layer that acts to protect that ice from sublimating away. When wind blows that dust off and the summer sun hits that near-surface ice, however, it does sublimate in bursts, which thus provides an explanation for the erosion that caused these low featureless plains.

As for these strange terraced mesas inside these distorted hollows, my guess is that the mesas predate the icesheet and are made of material with less ice impregnated within it. As that ice sublimates away it creates the craters within which the mesas remain. The terraces suggest a earlier series of geological sedimentary history.

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 27, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The picture was simply labeled a “terrain sample,” which usually means it was taken not as part of any specific research request, but to fill a gap in the schedule so as to maintain the camera’s proper temperature. When such gap-filler pictures are necessary, the MRO camera team tries to snap something of interest. Sometimes the pictures end up somewhat boring. This time however the picture highlights a dune field that is unusually light in color.

Since most Martian sand is volcanic in origin, it tends to look dark in orbital pictures. That this sand looks bright could be because it is inherently different, or it could be that lighting conditions make what normally looks dark to look bright instead.
» Read more

Click for original image.

Today’s cool image is another example of what I call a “What the heck!” image. The picture to the right, simply cropped to post here, was taken on September 22, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

It shows what the scientists label as “etched terrain,” an incredibly twisted and eroded landscape that to me actually defies description. In trying to research what scientists have learned and theorized about this terrain, it appears they think it is material that flowed over older terrain (thus its lack of many craters) that was subsequently eroded by later processes.

Why it eroded so strangely however is not really understood. It could have been caused by near-surface ice sublimated to the surface and thus causing many breaks, but since this terrain is located right on the equator in the dry tropics, it is a very long time since water was present here.
» Read more

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 9, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The white dot on the overview map above marks the location, inside the deep enclosed and very large 130-mile-wide depression dubbed Juventae Chasma.

The mountain in the picture raises above the sand sea that surrounds it from 1,000 to 2,300 feet, depending on direction, as the downhill grade of the sand sea is to the east. Thus, on the west the mountain rises less, while on the east the height is the greatest.

The inset illustrates the extent of the sand sea. It covers the ground for many miles in all directions. The way the sand surrounds these mountains suggests the prevailing winds blow from the west to the east. In fact, the facts suggest that this sand is volcanic ash that was blown into Juventae from many eruptions that occurred over time to the west, where it got trapped. The wind and gravity deposited the sand into the 20,000 to 25,000-foot-deep chasm, where the wind was insufficient to lift it out again.

One wonders how deep that sand sea might be. The lack of any surface features at all suggests it could be quite deep, burying everything but the highest peaks. In fact, if a geologist could drill a core through that sand I suspect he or she might be able to document the entire eruption history of much of Mars.

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on August 20, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labels the entire picture simply as “gully,” obviously referring to that distinct and somewhat deep hollow in the middle of the picture.

Most gullies that have been found on Mars tend to look more eroded and rougher than this hollow. Here, it appears almost as if the process that caused this gully occurred relatively recently, resulting in its sharp borders that have not had time to crumble into softer shapes.

The crater interior slope is about 1,500 feet high. Whatever flowed down it however did not do it in an entirely expected manner. As it flowed it curved to the west, so that the impingement into the glacial material that fills the crater floor is to the west of the gully itself. Either that, or that impingement was caused by a different event at a different earlier time.
» Read more

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on August 10, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

My reason to posting this I admit is selfish and tourist-oriented. This narrow ridge, about a mile long and about 300 to 600 feet high, appeals directly to my hiking passions. A trail along its length would provide any hiker some really spectactular views.

The scientists took the picture because of the geology. The white dot on the overview map above marks the location, a short channel dubbed Daga Vallis that connects two major canyons in the eastern part of Valles Marineris, the largest known canyon system in the solar system. This ridge and several nearby parallel ridges were apparently made of something, possibly lava, that was resistent to the theorized ancient catastrophic floods that scientists presently believe carved out these channels and canyons.

In the inset the dotted line indicates one possible hiking trail route that travels the full length of the ridge but then heads south to continue along the rim of a 1,200-foot-high cliff face. For future Martian colonists, I offer this site as a great place to set up a bed-and-breakfast, surrounded by many potential hikes of incredible stark beauty.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 17, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The white dot on the overview map above marks the location, inside a thirty-mile-wide dune sea, or erg, that sits in the center of the floor of 80-mile-wide Russell Crater.

That erg is interesting in that it appears the dunes get larger and larger as you move from the perimeter to its center. Thus, the dunes in the picture are called mega-dunes, about 200-feet-high. They dwarf the smaller dunes at the erg’s edge.

This picture was taken as part of a long term monitoring program to track the coming and going of seasonal dry ice frost on these dunes. It is summer when this picture was taken, so there is relatively little visible frost, though the bright blue areas in the color strip could possibly be the last remnants from winter. In winter, data suggests the entire surface of these dunes is covered by dry ice frost.

As the location is at 54 degrees south latitude, it likely sits at the northernmost edge of the southern dry ice mantle that in winter covers each of the Martian poles, down to about 60 degrees latitude.

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on August 16, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labels these strange features “ring-mound landforms,” a term that has been used to describe [pdf] only vaguely similar features previously found in the Athabasca flood lava plain almost on the other side of Mars. That paper suggested that those ring mounds formed on the “thin, brittle crust of an active fluid flow” created by an explosive event. Since Athabasca is considered Mars’s most recent major flood lava event, the fluid was likely lava, which on Mars flows more quickly and thinly in the lower gravity.

Thus, in Athabasca the ring-mounds formed when a pimple of molten lava from below popped the surface.

But what about the ring mounds in the picture to the right?
» Read more

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on August 19, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled merely as a “terrain sample,” it was likely snapped not for any specific research project, but to fill a gap in the camera schedule in order to maintain its proper temperature.

When the science team does this they try to pick interesting locations. Sometimes the picture is relatively boring. Sometimes, like the picture to the right, it reveals weird geology that is somewhat difficult to explain. The picture covers the transition from the smooth featureless plain to the north, and the twisting and complex ridges to the south, all of which are less than a few feet high.

Note the gaps. The downgrade here is to the west, and the gaps appear to vaguely indicate places where flows had occurred.
» Read more

Click for original image.

Today’s cool image returns to the same region yesterday’s cool image visited. The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 21, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It was clearly taken to get a close look at this unusual pointy mesa.

MRO elevation data says this mesa is about 800 feet height. The color difference between the north and south flanks suggests the accumulated presence of dust on the north, suggesting the prevailing winds here come from the northeast and blow to the southwest. This conclusion is reinforced by the dark accumulated dust found in the southwest quadrants of all the crater floors in the full image. The wind blows this dust into the craters, where it gets trapped against the southwest crater wall.

Note the mesa’s wide base, with one crater partly eaten away on its eastern edge. The overall shape of this base suggests that it was carved by some flow coming from the southwest, as indicated by the arrow.
» Read more