Tag: geology

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Of all many cool images I’ve posted, today might take the cake (pun intended) for the best illustration of the alien nature of Mars. The picture to the right, cropped, reduced, and sharpened to post here, was taken on June 28, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what the scientists simply label as “flow features.”

I personally don’t see any obvious flow features in the full image, unless one wants to call the brain terrain that covers this entire plain a flow feature. Brain terrain is a feature unique to Mars whose origin remains a mystery to geologists. As noted by scientists in captioned MRO image in 2019:

You are staring at one of the unsolved mysteries on Mars. This surface texture of interconnected ridges and troughs, referred to as “brain terrain” is found throughout the mid-latitude regions of Mars.

…This bizarrely textured terrain may be directly related to the water-ice that lies beneath the surface. One hypothesis is that when the buried water-ice sublimates (changes from a solid to a gas), it forms the troughs in the ice. The formation of these features might be an active process that is slowly occurring since HiRISE [MRO’s high resolution camera] has yet to detect significant changes in these terrains.

The wedding cake inside the small crater to the upper right only adds to the alienness of this terrain.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on July 3, 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 scientist’s specific research program but to fill a gap in the camera’s schedule in order to maintain its proper temperature. When the camera team needs to do this they try to pick something of interest that is below during that gap.

In this case MRO was over the vast flood lava plains of Mars where for many hundreds of miles the only features are small variations produced from different overlapping lava flood events. The layers of lava in this region in fact appear so thick that there are relatively few places where the older topography still sticks up through the lava. In the case of this picture, the ridges might indicate such buried topography, but they also might simply be dikes of lava, pushed up through fissures from underground.
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Cool image time! The picture to the right, cropped and reduced to post here, was taken on June 30, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The scientists label these features “cones” because many of the depressions sit on top of a mound or hill, suggesting some form of volcanic feature, either from erupting lava, ice, or mud.

Yet, are they volcanoes? Some or even many could instead be impact craters, created when a asteroid broke up during infall, creating a spray of bolides. Erosion of surrounding terrain can create what scientists call pedestal craters, but if all these craters were from an impact than all would either be pedestal craters, or not. Instead, we have a mix of some craters above and others level with the terrain.
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Cool image time! The picture to the right, cropped, reduced, sharpened, and annotated to post here, was taken on May 21, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows one of Mars’ more impressive mountains with the Sun somewhat low in the western sky, resulting in the long dark shadows on the eastern slopes.

The line is my quick attempt to mark the obvious route that would be taken along that ridge line to get from the bottom to the top. This could be a hiking trail, or a road. In either case, the elevation gain from the bottom of the ridge to the plateau on top would be about 3,900 feet in about a mile and a half, very steep for Earth — at approximately a 26 degree grade — but probably quite doable in the one-third Martian gravity.

The lower end of my proposed route however is hardly the bottom of the mountain. The slope, now alluvial fill made up of dust and debris from above, continues downhill for another 5,400 feet. All told, from top to bottom the elevation gain is about 9,300 feet over 8.5 miles.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on June 2, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows one small area in Martian equatorial regions where the main features are a dusty plain interspersed with craters, not entirely dissimilar to the Moon .

In the picture the northwest-to-southeast orientation of ridge-lines, plus the position of divots with their steep and deep end all on the northwest side, all suggest the prevailing winds here blow in the same direction, from the northwest to the southeast.

We are looking at a very ancient terrain. Many of these craters likely date from the early bombardment period of the solar system, just after the planets had formed but there was still a lot of objects around crashing into them.
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Cool image time! The picture to the right, cropped and reduced to post here, was taken on March 24, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) as part of a long term monitoring program of the many Martian gullies scientists have found above 30 degrees north latitude on a variety of slopes.

Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars. They are named for their resemblance to terrestrial gullies. First discovered on images from Mars Global Surveyor, they occur on steep slopes, especially on the walls of craters. Usually, each gully has a dendritic alcove at its head, a fan-shaped apron at its base, and a single thread of incised channel linking the two, giving the whole gully an hourglass shape. They are estimated to be relatively young because they have few, if any craters.

…Most gullies occur 30 degrees poleward in each hemisphere, with greater numbers in the southern hemisphere. Some studies have found that gullies occur on slopes that face all directions; others have found that the greater number of gullies are found on poleward facing slopes, especially from 30° to 44° S. Although thousands have been found, they appear to be restricted to only certain areas of the planet. In the northern hemisphere, they have been found in Arcadia Planitia, Tempe Terra, Acidalia Planitia, and Utopia Planitia. In the south, high concentrations are found on the northern edge of Argyre basin, in northern Noachis Terra, and along the walls of the Hellas outflow channels.

Orbital data has identified almost 5,000 gullies on Mars. Based on their shape and the Martian climate, scientists generally think these gullies were formed by some form of water flow, possibly coming from an underground aquifer at their top.
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Today’s cool image illustrates the complex explanations scientists sometimes have to come up with explain the strange geology seen on Mars. The picture to the right, cropped, reduced, and sharpened to post here, was taken on May 30, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as a whitish “ridged flow-like feature” that appears to exit out of the massive hill to the west.

The white dot on the overview map above as well as in the inset marks this location, smack dab inside the 2,000-mile-long strip of glacier country in the Martian northern mid-latitudes. As you can see from the inset, that massive hill is actual the foot of a large apron of material, likely ice-infused, that has sagged down from the large 5,400-foot high mesa to the west.

The white material is likely what the scientists call an inverted river. Once it was a channel in which either water or ice flowed. With time the weight of that material compacted the riverbed so that it was denser than the surrounding terrain, much of which was likely soft anyway because of a high ice content. When that surrounding terrain eroded away, the riverbed resisted that erosion, and instead became the raised ridge we now see.

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Cool image time! The picture to the right, rotated, cropped, and sharpened to post here, was taken on May 14, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small section of a vast dune field, 50 miles square, that sits about 225 miles south of the southern foothills of Mars’ biggest volcano, Olympus Mons.

The dunes are probably less than 20 feet high, with that one small hill only slightly higher. Their similar orientation, which extends across the entire 50-mile-square dune field, indicates the direction of the prevailing winds, which I think (but will not swear to it) is from the southeast to the northwest, which also happens to also follow the grade downhill to the northwest.

It is also possible that wind direction is the reverse, and goes uphill to the southwest.
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