Tag: Mars

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Cool image time! The photo to the left, cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on January 21, 2020, and shows several boulders at the bottom of a slope, along with the tracks those boulders made as they rolled downhill sometime in the far past.

Uphill is to the south. We know the dark spots at the end of these tracks are large boulders partly because of the wind streaks emanating away from them to the north. As the wind goes around each rock it produces eddies that produce the tracks. Based on the scale and the image resolution (about 10 inches per pixel), these boulders range in size from about one to five feet in diameter.

This image has two points of interest. First, the tracks left by the boulders seem to have a repeating pattern. My guess is that the pattern most likely formed because the boulders are not spherical in shape, and as they rolled each roll repeated a certain pattern reflecting that shape. This theory is reinforced by a close look at each boulder. Though the resolution is insufficient to resolve the boulders themselves, the pixel distribution for each strongly suggests an asymmetric shape.

Second, this image, when compared with an earlier MRO image of the same spot, taken fourteen years ago in December 2006, shows no obvious change. These tracks, and their boulders, have therefore probably sat here, as we see them, for a long time. Since there appear to be two sets of tracks, with one overlying the other, this suggests that two separate events (an earthquake or nearby impact) each time caused a bunch of boulders to break free and roll downward together, with the second set of boulder tracks crossing over the earlier set.

Establishing when those two events occurred, however, will require some on-site data, something that will likely not occur until humans roam the surface of Mars in large numbers.

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Cool image time! The photograph to the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on December 22, 2019 and was titled “Contact Between Debris Apron and Upper Plains in Deuteronilus Mensae”.

The section of the full image that I have focused on shows what appears to be the downhill break-up of the surface debris covering an underlying water ice glacier. The grade is downhill to the south.

I am confident that this is buried glacial material based on recent research:

• November 22, 2019: Mars Express confirms ancient glaciers in northern Martian mid-latitudes
• December 20, 2019: More evidence of ample shallow ice in Martian mid-latitudes

Both of these reports found lots of evidence of shallow ice in Deuteronilus Mensae, a region of chaos terrain in the transition zone between the Martian northern lowlands and the southern highlands.

With this image we see what appears to be the slippage of that ice downslope, causing breakage and cracks on the surface, with much of that surface made up of the dust and debris that covers the ice and protects it. Towards the bottom of the image it even appears that the disappearing ice is unveiling the existence of a bunch of buried bedrock mesas, typical of chaos terrain, previously hidden by the ice because it filled the surrounding canyons.

Below is a close-up of the photograph’s most interesting area of break-up.
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Cool image time! The photo on the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on November 21, 2019. The uncaptioned image was simply entitled “Ice-filled Graben.”

The location is on the lower flanks of the giant volcano Alba Mons, which in itself sits north of Olympus Mons and the volcanic Tharsis Bulge. The canyon is called a graben because it was formed when a section of the crust slips downward along parallel faults. It does not have the features of a rill, or lava flow, as it starts and stops suddenly. It probably formed due to the rise of the volcano, pulling apart its flanks along faults, causing some sections then to slip downward.

How do the scientists know this is ice-filled? I suspect they have other data that indicates the presence of water, but there are also clear features inside this canyon that resemble the glacial features found elsewhere on Mars. For example, note the parallel lines near the canyon walls. These indicate past surface levels as well as layers within the ice from cyclic climate processes. The line of pits along the southwest wall, where the surface gets more sunlight, also suggests that this sunlight is causing more ice to sublimate away.

Finally, the graben is located at 46 degrees north latitude, definitely far enough north for such ice to exist, based on ample other research.

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The image to the right, rotated, cropped and reduced to post here, was taken on December 19, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled “Head of Mamers Valles”, it shows the very end of one side canyon to this very extensive canyon system made up of the fractured fissures and mesas of chaos terrain.

Mamers Valles itself sits in the transition zone between the northern lowland plains and the southern cratered highlands. This specific canyon is close to those lowlands, at a latitude of 40 degrees north, where scientists believe there are many buried inactive glaciers of ice.

The image reinforces this belief. The entire canyon appears practically filled with what looks like ice. In fact, it almost looks like we are looking down at a frozen lake with a layer of snow on top of it. In this case, the layer is not snow, but dust and dirt and debris that covers the ice to protect it and prevent it from sublimating away.

The overview map below shows the location of this canyon, by the red cross, within Mamers Valles.

Mamers Valles is actually a very large collection of miscellaneous canyons, flowing into the lowlands. In some areas it looks like very old chaos terrain, with the canyons so eroded that all we see are scattered mesas. In other places the canyons more resemble meandering river canyons sometimes interspersed with crater impacts.

Scientists have analyzed the canyons in Mamers Valles, and from this concluded that they were likely formed from “subsurface hydrologic activity”. which in plain English means that flowing water below ground washed out large underground passages, which eventually grew large enough for their ceilings to collapse and form the canyons we see today.

Yesterday I posted an image of a string of pits that could very well be evidence of this same process in its early stages of canyon formation. In Mamers Valles the process is far more advanced, and the canyons have existed for a long time, long enough for the planet’s inclination to go through several cycles of change, from a low of 25 degrees tilt (what it is now) to has high as 60 degrees. At that high inclination the mid-latitudes were colder than the poles, so that ice would sublimate from the poles to fall as snow in the mid-latitudes, forming active glaciers within canyons such as this.

Now that the planet’s inclination is similar to Earth’s, 25 degrees, the poles are slightly colder than the mid-latitudes, and the glaciers in this canyon are either inactive (if buried) or slowly sublimating away so that the water can return to the poles.

Here however the surface debris appears to be protecting the glaciers, leaving the canyon filled mostly with ice. For future settlers this ice would likely be relatively accessible, and at a latitude where the environment is also relatively mild, for Mars.

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Cool image time! The photo to the right, rotated, cropped and reduced to post here, was taken on January 3, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows three strange teardrop-shaped depressions, clearly wind-swept and partly buried by dust and sand.

The location on Mars of these depressions is in the transition zone between the southern cratered highlands and the northern lowlands. This is also a region dubbed the Medusae Fossae Formation, a region where it appears a great deal of volcanic material was laid down during one or more eruptive events 3 to 3.8 billion years ago.

Whether these depressions were formed during those events is impossible to tell from the available data, especially because the underlying bedrock is buried in dust.

Their shape appears to have been caused as the wind slowly exposed three buried peaks of hard rock. The wind, blowing from the southwest to the northeast, would hit the peaks, producing an downward eddy that would churn out dust from the windward side. The wind and dust would then blow around the peaks, creating the teardrop tail on the leeward side to the northeast.