Tag: geology

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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on January 11, 2023 by the high resolution camera on Mars Reconnaissnace Orbiter (MRO).

The scientists labeled this picture “Rocky Terrain.” Though this describes the overall sense of the full image, it fails to capture correctly the nature of this patch of ground at the center of the picture. As you can see, this patch of spongelike surface starts and ends abruptly. It appears that it is a layer on top of the surrounding terrain that has also been eroded aggressively since its placement.

The many craters on its surface seem to have come later, though as the crater size diminishes it becomes harder to separate the craters from the sponge holes. Moreover, some of the larger craters are distorted in shape, as if the impact hit material that was viscous and could flow somewhat.

The overview map below gives some context, but only some.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 20, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a strange terrain of craters and mounds, with all the mounds having pits within them like volcanic calderas. In between the surface has a two-toned stippled look, as if two different materials are in the process of mixing.

My immediate impression was that of the bubbly surface of a vat of tomato sauce simmering. Or maybe the vile mixture created by the witches in Shakespeare’s Macbeth, which as they mix they chant:

First witch:
Round about the cauldron go;
In the poison’d entrails throw.
Toad, that under cold stone
Days and nights has thirty-one
Swelter’d venom sleeping got,
Boil thou first i’ the charmed pot.

ALL:
Double, double toil and trouble;
Fire burn, and cauldron bubble.

Of course, this is not a vat of witch’s brew or tomato sauce. It is the surface of the planet Mars, but an alien surface nonetheless.
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Cool image time! The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken on January 27, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what the scientists label a “streak-spoke pattern” inside the crater. To my eye, the pattern more resembles hanging draperies, neatly tied near the top and then pulled apart as they descend to the ground.

This photo was a follow-up to a previous picture by MRO on February 4, 2008, more than seven Martian years ago, to see if there had been any identifiable changes in that time. Both images were taken in springtime, and despite the passage of time, the 2023 image shows no obvious changes from the 2008 photo.

What caused this distinct pattern? The first guess would be the wind, except if so shouldn’t there have been some change over seven Martian years?
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Today’s cool image illustrates once again the importance of looking not simply at the picture but at the surrounding larger context in order to understand the Martian features within the photograph.

The photo to the left, cropped, reduced, and sharpened to post here, was taken on January 31, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The location is at 26 north latitude, so it is in the dry equatorial regions. It shows what appears to be a large Martian flood lava plain, with at least two different flood lava events appearing to flow to the northeast, with the second only partly covering the first.

From this high resolution image it seemed probable that the source of the flow was from the southwest, an assumption that at first glance is strengthened by the overview map below.
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Cool image time. The picture to the right, cropped to post here, was taken on February 2, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows a strangely blobby crater in the northern mid-latitudes where glacial features are frequently found inside craters.

In this case however the glacier seems very confused. As this is in the northern hemisphere, you would expect glacial material to survive on the north-facing southern interior slopes of the crater, where there is year-round less sunlight. The mottled eroded terrain in the south part of the crater floor suggests this. However, the crater also clearly has a terraced glacier on its south-facing northern interior slopes.

Why has the glacial material survived in both places, but not in the center of the crater?

In addition, there is that strange roughly circular feature attached to the south side of the crater. What formed it? Is it a glacier on the plains surrounding the crater? Or are we looking at volcanic material?

This crater is also unique. The crater just to its southwest (partly seen in the cropped image above), is a much more typical glacial-filled mid-latitude crater, its interior material more evenly distributed and its circular rim only slightly distorted.
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Cool image time! The picture to the right, cropped and reduced to post here, was taken on December 24, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows erosion gullies coming down off a mountain side, just north of a massive cliff that I estimate to be around 2,000 to 3,000 feet high.

Note the north-south-trending cracks. These suggest that this entire half-mile-high cliff face is slumping downward, cracking as it does so. The cracks at the start of the high flat-topped thumb-shaped mesa near the image bottom are especially intriguing. They suggest that this entire mesa might eventually separate and give way.

There is a specific reason this cliff face is slumping, as shown in the overview map below.
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Cool image time! The picture to the right, rotated, cropped, rotated, and sharpened to post here, was taken on November 28, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled merely as a “crater with mesa”, it gives us another example of the presence of glacial ice in the mid-latitudes of Mars.

That mesa is what planetary scientists have labeled “concentric crater fill,” a glacial feature found in numerous craters throughout the mid-latitude bands from 30 to 60 degrees latitude. The ground in the terrain surrounding the crater could be also be impregnated with ice, but based on the location as shown in the overview map below, it is just as likely to be lava.

In fact, the location of this particular crater illustrates why concentric crater fill might become the best source of ice for future colonists.
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Scientists have uncovered geological evidence of a past glacier in westernmost end of the giant Martian canyon Valles Marineris, right at the point where it transitions into the complex chaos region dubbed Noctis Labyrinthus. The white dot on the map to the right indicates the location.

The surface feature identified as a “relict glacier” is one of many light-toned deposits (LTDs) found in the region. Typically, LTDs consist mainly of light-colored sulfate salts, but this deposit also shows many of the features of a glacier, including crevasse fields and moraine bands. The glacier is estimated to be 6 kilometers long and up to 4 kilometers wide, with a surface elevation ranging from +1.3 to +1.7 kilometers. This discovery suggests that Mars’ recent history may have been more watery than previously thought, which could have implications for understanding the planet’s habitability.

“What we’ve found is not ice, but a salt deposit with the detailed morphologic features of a glacier. What we think happened here is that salt formed on top of a glacier while preserving the shape of the ice below, down to details like crevasse fields and moraine bands,” said Dr. Pascal Lee, a planetary scientist with the SETI Institute and the Mars Institute, and the lead author of the study. [emphasis mine]

You can read the paper here [pdf]. The research specifically suggests that near surface water ice in the dry equatorial regions of Mars could have been there much more recently that previously believed. It also suggests, by the rarity of this discovery, that there is likely almost no near surface ice in the equatorial regions, at present.