Tag: geology

More Martian Pits!

1:11 pm

More pits on Mars!

As I said in my last post in February showing recent pit discoveries on Mars, I could almost make this a monthly series. In the March image download from the high resolution camera of Mars Reconnaissance Orbiter (MRO) were three (maybe four) more pits, all likely skylights above lava tubes and all located near the giant volcano Arsia Mons in the region dubbed the Tharsis Bulge. The image to the right shows all three, with a possible fourth just northwest of pit #2 and visible in its full image. For the full images of the other two pits go here (#1) and here (#3). In all three cases, click on the “black & white map projected” link to see the full image with scale.

Overview map

The overview map on right shows where these three pits are located. If you compare this map with my previous overview maps from November 12, 2018 and February 22, 2019 you can see that while these pits are all found on the volcanic slopes surrounding Arsia Mons, they are all different pits. Moreover, the ten pits listed in these three posts are only a small sampling of the more than hundred already found.

Whether these pits are deadend sinks or skylights into underground lava tubes that connect is at this point unknown. It would be a reasonable speculation to assume that some are deadends, and some link to extensive tubes of varying lengths. It would also be dangerous. Mars is alien. While the geology will be based on the same physical laws found on Earth, the lighter gravity is going to produce things differently.

The three images above however do show some intriguing details.
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Circular feature on Mars?

2:52 pm

A circular feature on Mars?
Click for full resolution image.

Today’s cool image is cool for two reasons. First and foremost, the image, found in the archive of the high resolution camera of Mars Reconnaissance Orbiter (MRO), is titled “Circular Feature.” On the right is the full image, reduced to post here. I have searched it high and low, at low resolution as well as full resolution, and can find nothing, nothing at all, that invokes a circular feature to me.

This strange terrain is located very close to the southern icecap. If anything, the knobs and features that fill this image remind me of brain terrain, partly obscured by a layer of partly melted snow or frost. Nothing however seems circular in the slightest.

The second reason this image is cool is that it is very representative of its very large surrounding region. For what appears to be several hundred miles in all directions this is all that one can see, in a variety of MRO images, here, here, here, here, here, and here, to show only a few. Ever so often a craterlike feature pops out, like in the last example, but generally the surface continues in this undulating bland manner, endlessly. The only changing aspect is the dark streaks that cut across, likely dust devil tracks made over a long period of time.

Below the fold is a section of the full resolution image, at full resolution. It doesn’t really matter where I took the crop, as anywhere in the full image everything looks pretty much the same. The only slow change that I can perceive is that the surface seems to be descending to the north, with the lighter areas implying the existence of terraces.

Take a look, and try to figure out for yourself what is going on here.
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Strange craters in the Martian northern lowlands

12:58 pm

Strange crater in the northern lowlands
Click for full image.

Cool image time! The image on the right, cropped and rotated to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and released in the monthly image dump provided by the science team. The release had no caption. It merely described this as a “Layered mound in crater.”

That is certainly what is is. However, layering suggests a regionwide process. The crater to the immediate northeast (the rim of which can be seen in the upper corner of this image), does not have the same kind of layering. (Be sure to click on the image to see that other crater.) Its crater floor is instead a blob of chaotic knobs, with the only layering scattered in spots along its north interior rim.

That the layering of both craters favors the north suggests a relationship, but what that is is beyond me. Prevailing winds? Maybe, but I don’t have the knowledge to explain how that process would work.

It is not even certain that these two craters were formed by impact. They are located in the northern lowlands where an intermittent ocean is believed to have once existed, and thus might be remnants of that ocean’s floor. That they both have a muddy appearance reinforces this hypothesis, but once again, I would not bet much money on this theory. The features here could also be expressing the effect of an impact on a muddy seafloor.

In either case the craters imply that the ocean that might have once been here existed a long enough time ago for these craters to form (either by impact or some other process) and then evolve. This has been a relatively dry place for a very long time.

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The layering at the Martian poles

2:56 pm

Layering in the east side of Burroughs Crater
Click for full image.

Layering in the west side of Burroughs Crater
Click for full image.

In the past month the science teams of both Mars Reconnaissance Orbiter (MRO) and Trace Gas Orbiter (TGO) have released images showing the strange layering found in Burroughs Crater, located near the Martian south pole.

The top image above is the MRO image, rotated and cropped to post here. To the right is a cropped and reduced section of the TGO image.

Though both images look at the inside rim of the crater, they cover sections at opposite ends of the crater. The MRO image of the crater’s east interior rim, with the lowest areas to the right, while the TGO image shows the crater’s northwest interior rim, with the lowest areas on the bottom. As noted at the TGO image site:
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Jezero Crater: The landing site for the Mars 2020 rover

12:21 pm

Jezero Crater delta
Jezero Crater delta

At this week’s 50th Lunar and Planetary Science Conference in Texas, there were many papers detailing the geological, topographical, chemical, meteorology and biological circumstances at the landing sites for the 2020 Martian rovers, Jezero Crater for the U.S.’s Mars 2020 and Oxia Planum for Europe’s Rosalind Franklin.

Most of these papers are a bit too esoteric for the general public (though if you like to delve into this stuff like I do, go to the conference program and search for “Jezero” and “Oxia” and you can delve to your heart’s content).

Oxia Planum drainages

These papers do make it possible to understand why each site was chosen. I have already done this analysis for Rosalind Franklin, which you can read here and here. Oxia Planum is in the transition between the southern highlands and the northern lowlands (where an intermittent ocean might have once existed). Here can be found many shoreline features. In fact, one of the papers at this week’s conference mapped [pdf] the drainage patterns surrounding the landing ellipse, including the water catchment areas, as shown by the figure from that paper on the right.

With this post I want to focus on Jezero Crater, the Mars 2020 landing site. The image above shows the crater’s most interesting feature, an impressive delta of material that apparently flowed out of the break in the western wall of the crater.

This image however does not tell us much about where exactly the rover will land, or go. To do that, we must zoom out a bit.
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Lava tubes on Alba Mons

12:28 pm

Lava tubes on the western slope of Alba Mons

During oral presentations today at this week’s 50th Lunar and Planetary Science Conference in Texas, scientists revealed [pdf] a map showing what they believe are numerous lava tubes flowing down the western slope of the giant Martian volcano Alba Mons.

The image on the right is taken from their paper. The red lines indicate collapsed tube sections, maroon collapsed sections on a ridge, and yellow volcanic ridges, which I assume are external surface flows. From their paper:

Lava tube systems … occur throughout the western flank, are concentrated in some locations, and are generally radial in orientation to Alba Mons’ summit. Lava tubes are typically discontinuous and delineated by sinuous chains of elongate depressions, which in many cases are located along the crests of prominent sinuous ridges. Lava tube systems occur as both these ridged forms with lateral flow textures and more subtle features denoted by a central distributary feature within the flat-lying flow field surface. Significant parts of the sinuous volcanic ridges show no collapse features, indicating a distinctive topographic signature for Alba Mons’ lava tubes.

Alba Mons is in some ways the forgotten giant volcano on Mars.
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Streaky Mars: Slope streaks and recurring slope lineae

12:01 pm

New recurring lineae on Mars
Click for source paper [pdf].

Numerous presentations at this week’s 50th Lunar and Planetary Science Conference in Texas have focused on two different changing features on the Martian surface, dubbed slope streaks and recurring slope lineae (or RSLs, an example of an unnecessary and unwieldy acronym that I avoid like the plague).

These apparently are considered two different phenomenon (with some overlap), something I had not recognized previously. For example, one presentation [pdf] this week described slope streaks as:

…gravity-driven dark or light-toned features that form throughout the martian year in high-albedo and low-thermal-inertia equatorial regions of Mars. The distinctive features originate from point sources on slopes steeper than ~20°, follow the topographic gradient, extend or divert around small obstacles, and propagate up to maximum lengths of a few kilometers. The streaks brighten with time, sometimes become brighter than their surroundings, and fade away over timescales of decades. [emphasis mine]

An example can be seen here. This is in contrast to the recurring slope lineae, shown in the image above, which another paper [pdf] described as:

…dark linear features that occur on the surface of steep slopes in the mid-latitudes of Mars. These areas are warm, occasionally exceeding temperatures of 273-320 K. [Lineae] recur over multiple years, growing during warm seasons and fading away during colder seasons. Their apparent temperature dependency raises the possibility that liquid water is involved in their formation. [emphasis mine]

I have highlighted the key differences. While slope streaks are long lived and change slowly, lineae change with the Martian seasons. And the slope streaks appear to exist at lower latitudes. These difference means that the formation process of each must be also different.

The problem is that scientists still don’t know what causes either, though they have many theories, involving both wet and dry processes.

Most of the presentations at the conference this week focused on the recurring lineae, which I suspect is because of their seasonal aspect. This feature strongly suggests a water-related source for the lineae, and everyone who studies Mars is always focused on finding sources on Mars where liquid water might be found. Also, slope streaks appear more often in dunes, which also strongly suggests a dry process. One paper, however, did a comparison study of lineae with one specific kind of dune slope streak to see if the freatures might be related.

The most interesting result [pdf] for all these papers documented the apparent increase in recurring lineae following the global dust storm last year. The image at the top of that post is from this paper, and shows a fresh lineae where none had been prior to the storm. From the paper’s abstract:
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Land of mesas

9:44 am

Ariadnes Colles
Click for full image.

Cool image time! The Mars Odyssey science team today released the image on the right, cropped and rotated to show here, of a region on Mars named “Ariadnes Colles.”

The term colles means hills or knobs. The hills appear brighter than the surrounding lowlands, likely due to relatively less dust cover.

This is certainly a place with lots of hills, or to be more precise, mesas, as many of them seem to be flat topped.

The lack of dust cover on the tops is probably because, like on Earth, the winds blow much better once you get a bit above the surface. (This is why sailing ship builders kept adding higher and higher sails to their ships, until the top sails of clipper ships rose a hundred-plus feet above the deck.) These better winds clean off the mesa tops, just as they did to the solar panels on the rovers Opportunity and Spirit several times during their long missions.

Ariadnes Colles is another example of Martian chaotic terrain. Since this region is located deep in the cratered and rough southern highlands of Mars, the erosion that created these mesas was likely not water-flows. Was it wind? Ice?

Your guess is as good as anyone’s.

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Mars likely has many large and extensive cave systems

1:56 pm

Mamers Valles

More caves on Mars! This week the Lunar and Planetary Institute and the Johnson Space Center are jointly holding the 50th Lunar and Planetary Science Conference in Texas. I have been going over the program, and will be posting reviews of some of the more interesting results all this week.

We begin with caves, which should not be surprising to my regular readers. As a caver who also knows their value for future space colonists, I am always attracted to new discoveries of cave passages on other worlds. Today’s however is a doozy.

The image to the right is of Mamers Valles on Mars, what scientists have dubbed a fretted valley, a common feature in the transition zone between the low altitude northern plains and the southern highlands. It comes from a paper [pdf] with the typically unexciting scientific title, “Fretted channels and closed depressions in northern Arabia Terra, Mars: Origins and implications for subsurface hydrologic activity.”

What the scientists really means here is that their research strongly suggests that Mars has a very large and very extensive number of underground drainage systems, which have caused collapses on the surface that often resemble meandering river canyons, such as seen above. As they explain:
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Martian massive landslides

1:24 pm

Though scientists have found some evidence of slow erosion and change on the Martian surface, it is today generally inactive. While the weak wind of Mars’ thin atmosphere continues to work its will, and the likely presence of underground frozen water acts to shift the surface shape as the seasons come and go, none of this happens quickly.

Essentially, Mars is a quiet place.

Once however catastrophic events took place, gigantic floods flowing down to the east from the planet’s huge volcanoes to carve out Marineris Valles, the solar system’s largest known canyon. As that water rushed eastward it ripped the terrain apart quickly, creating deep side canyons, drainage valleys, and chopped up regions now dubbed as chaos terrain, multiple mesas separated by numerous fissure-like canyons.

Overview of Marineris Valles and landslide

The overview map on the right shows Valles Marineris and its drainage to the east and north into the vast northern plains of Mars. It also shows the location of one of the largest regions on Mars of chaos terrain, dubbed Hydraotes Chaos, located close to the mouth of this gigantic drainage system more than 2,500 miles long.

Massive Martian landslide
Click for full image.

Recently scientists have used the high resolution camera on Mars Reconnaissance Orbiter (MRO) to begin taking images of the massive landslides on the face of the mesa north of Hydraotes Chaos that was hit directly by these floods. The location of the most immediately interesting of these landslide images is also indicated on this overview image.

To the right is that image, rotated, cropped, reduced, and annotated to post here. The white boxes indicate two full resolution sections that I highlight below at full resolution.

This image shows that full cliff. The total drop from the plateau at the top to the floor where Hydraotes Chaos is located to the south is approximately 8,200 feet, almost exactly comparable to the depth of the north rim of the Grand Canyon.

The image shows numerous evidence of avalanches and erosion, both at its base and at its rim. None of these avalanches likely occurred during those catastrophic floods, but long afterward.
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Brain Terrain on Mars

7:48 pm

Brain terrain on Mars
Click for full image.

Cool image time! This week the Mars Reconnaissance Orbiter (MRO) science team featured four new captioned images taken by the spacecraft and released as part of the March image dump. The first, dubbed “The Slow Charm of Brain Terrain,” deserves an immediate post on Behind the Black. To the right is only a small section cropped from the full image. From the caption:

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 image is in Protonilus Mensae.)

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.

Below is a cropped section of the full image, rotated and reduced to post here.
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Another batch of caves/pits found on Mars

1:10 pm

Four new pits on Mars

Overview of February 2019 pits

In the past year the monthly image releases from the high resolution camera on Mars Reconnaissance Orbiter (MRO) archive have frequently included newly discovered pit entrances. Each time I have written posts highlighting these new pits, in June, July, November 2018 and January 2019. In fact, this is happening so frequently I could almost label it a monthly update!

The November release imaged three pits found on the southern flanks of Arsia Mons. The January 2019 release found several north of the volcano, two of which are very close to the two middle new pits highlighted above. The February release, which is the focus of this post, included four more pits, shown above, all located north and west of Arsia Mons, as shown in the overview map to the right.

Pits 2 and 3 above appear to belong to a cluster of pits all located in the general area between Arsia and Pavonis Mons. (You can see their uncaptioned releases here and here.) Most sit alone on a flat somewhat featureless plain. Sometimes there are flow features nearby, but each pit usually seems to sit unique and unrelated to these other faint features.

Pit 1 is very intriguing in that it sits amid a very long chain of pits and canyons, all aligned, as shown in the image below and to the right.
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Monitoring a fresh-looking Martian landslide

4:09 pm

2012 image of Martian landslide
Click for full image

2018 image of Martian landslide
Click for full image

Time for two cool images! To the right are two images taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO), the top one taken in April 2012, and the bottom taken in December 2018. Both have been cropped and reduced slightly in resolution to post here.

The second image is trying to answer, in only a small way, one of the most fundamental questions of the Martian environment: How fast does it change? The images from orbit have periodically seen evidence of new impacts. MRO images have tracked dust devil tracks. And we know that somehow water, ice, wind and volcanic activity have eroded and reshaped the surface over eons.

What we don’t know truly and with detail is the pace of these changes, with any accuracy. The pace of some things over time seems obvious. For example, Mars’s inactive but gigantic volcanoes suggest that once volcanism was very active, but over time has ceased so that today it is unclear if any is occurring. Similarly, the geological evidence suggests that in the far past water flowed on the surface, producing catastrophic floods. Now that liquid water is all but gone, and this erosion process as ceased.
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A second Greenland crater discovered?

11:04 am

Scientists are now claiming they have found a second crater buried under Greenland’s icecap.

To confirm his suspicion about the possible presence of a second impact crater, MacGregor studied the raw radar images that are used to map the topography of the bedrock beneath the ice, including those collected by NASA’s Operation IceBridge. What he saw under the ice were several distinctive features of a complex impact crater: a flat, bowl-shaped depression in the bedrock that was surrounded by an elevated rim and centrally located peaks, which form when the crater floor equilibrates post-impact. Though the structure isn’t as clearly circular as the Hiawatha crater, MacGregor estimated the second crater’s diameter at 22.7 miles. Measurements from Operation IceBridge also revealed a negative gravity anomaly over the area, which is characteristic of impact craters.

“The only other circular structure that might approach this size would be a collapsed volcanic caldera,” MacGregor said. “But the areas of known volcanic activity in Greenland are several hundred miles away. Also, a volcano should have a clear positive magnetic anomaly, and we don’t see that at all.”

It must be emphasized that this conclusion remains very uncertain. What they have found is a depression that has features indicative of an impact crater, data that is far from sufficient to definitively prove the crater is real.

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Mysterious dark-toned Martian terrain

12:37 pm

Dark toned ridge in Martian southern highlands
Click for full resolution image

Cool image time! The picture on the right, cropped and reduced to post here, was part of the January image release from the high resolution camera of Mars Reconnaissance Orbiter (MRO). It shows an area in the Martian southern highlands where the surface suddenly gets darker, for no obvious reason.

The uncaptioned release image is titled “Dark-Toned Ridge at Junction with Dark-Toned Plain.” From the image itself it is hard to understand this title. In the full image the darkest terrain is a strip in the center, with slightly lighter dark terrain on either side, and the lightest terrain to the north or south. The photograph however does not show us how far this dark terrain extends to the west or east.

Two Mars Odyssey image strips of less resolution, here and here, show that this region is filled with several large patches of dark-tone surface. With this particular patch the center dark ridge is surrounded by that slightly lighter dark area.

MRO itself has not taken many images of this region, as shown in the overview image below. The red rectangles indicate MRO’s high resolution photographs, with this image indicated by the cross. At this low resolution this region seems somewhat nondescript. The Mars Odyssey image strips show that there many features here, but with little significant relief.

Location of dark toned ridge

At high resolution there does not appear to be much difference between the darker and lighter areas. The lighter areas in general seem less rough and at a slightly lower elevation, but both areas are dominated by ridges and dunes trending southwest-to-northeast.

Why is this slightly higher region darker? Let’s assume that this darker material was a lava flow overlaying the surface. Over eons wind erosion, trending southwest-to-northwest, roughly eroded both it and the lower layers around it, leaving behind this rough corroded terrain. The different make-up of the darker material allows it to erode in a rougher manner.

While possibly correct, I would not bet much money on this guess. It is not clear it is lava. It is not clear that it is a flow. It does not explain why there are two areas of different darkness. And it certainly not clear what the make-up of any of this stuff is.

This is simply another cool mystery on the Martian surface.

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The location for a future Martian colony?

2:03 pm

Pit draining into Kasei Valles

Regular readers of this webpage will know that I am a caver, and am fascinated with the pits and caves that have so far been identified on Mars, as illustrated by an essay I wrote only last week.

Some of the cave research I have cited has being led by planetary scientist Glen Cushing of the U.S. Geological Survey. Two weeks ago Dr. Cushing sent me a slew of pictures of caves/pits that he has accumulated over the years, many of which he has not yet been able to highlight in a paper. At least two were images that I had already featured on Behind the Black, here and here.

One pit image however I had never seen. A cropped and reduced close-up is shown on the right, with the full photograph viewable by clicking on the image. In many ways this pit is reminiscent of many pits on Mars. Its northern rim appears to be an overhang several hundred feet deep that might have an underground passage continuing to the north. The southern lip is inviting in that its slope appears to be very accessible for vehicles, meaning this pit/cave might be a good location to build a first colony.

Because of that accessible southern lip, I decided to do more digging about this particular pit. I was quickly able to find the uncaptioned release of the complete image by doing a quick search through the image catalog of Mars Reconnaissance Orbiter’s (MRO) high resolution camera. That image, reduced and cropped to post here, is shown below, on the right.
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The many pits/caves of Mars

2:35 pm

Sinkhole in Martian northern lowlands with dark seep

Time for many cool images! Over the years I have written frequently about the pits/caves on Mars, in both magazine articles and the many posts here at Behind the Black. The following posts are the most significant, with the June 9, 2015 providing the best geological background to many of these pits, especially the many located near the giant volcanoes of Mars.

As I wrote in that June 9, 2015 post:
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Well water likely available across Mars

1:49 pm

Conceptual model of Martian deep basin evolution

A science paper released today and available for download [pdf] cites evidence from about two dozen deep impact craters located from the equator to 37 degrees north latitude that Mars has a ground ice table at an elevation that also corresponds to other shoreline features. From the abstract:

Observations in the northern hemisphere show evidence of a planet‐wide groundwater system on Mars. The elevations of these water‐related morphologies in all studied basins lie within the same narrow range of depths below Mars datum and notably coincide with the elevation of some ocean shorelines proposed by previous authors.

The image above and on the right shows the middle stage of their conceptual model for the evolution of these deep basins and how that evolution results in many of the geological features seen in many places on Mars, such as the features I have highlighted on Behind the Black previously here and here.

From their conclusion:
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Weird Martian fracture feature

1:24 pm

Fractured collapse feature on Mars

Cool image time! When I first looked at the high resolution Mars Reconnaissance Orbiter (MRO) image on the right, my immediate reaction was, “What the heck is that?” The image to the right is cropped and reduced, but if you click on it you can see the full image at high resolution.

The fractured terrain appears to be all within a collapse. To my eye it appears that while the overall surface has sunk, the fractures indicate an area where there has been an eruption upward, which after the eruption collapsed again, so that the fractured area remains at the apparent bottom of the collapse sink. I was immediately reminded of Upheaval Dome in Yellowstone National Park, which some geologists believe was formed by a “salt bubble” rising upward to create a salt dome.

A thick layer of salt, formed by the evaporation of ancient landlocked seas, underlies much of southeastern Utah and Canyonlands National Park. When under pressure from thousands of feet of overlying rock, the salt can flow plastically, like ice moving at the bottom of a glacier. In addition, salt is less dense than sandstone. As a result, over millions of years salt can flow up through rock layers as a “salt bubble”, rising to the surface and creating salt domes that deform the surrounding rock.

Context image for fracture feature

The process and materials involved were certainly different on Mars. Nonetheless, it does appear we are looking at an eruptive feature unrelated to molten lava. The context image to the right, showing this feature’s location in Mars’ vast northern lowlands, also shows that it has occurred on terrain that has bulged upwards relative to the surrounding lowlands. Nearby MRO images also show similar bulge/collapse features.

To decipher the geological mystery here, we would also need to know when this happened and whether there ever was a liquid ocean residing on top of it, before, during, or after the eruption. We also do not know well the make-up of the underground materials, including whether any frozen water and salt is present.

To be honest, we really don’t know much. I am sure a planetary scientist studying this feature could fill us in on some of these details, such as information provided by the colors in the color image. Even so, I am sure any good scientist would also admit to unknowns.

To get some real answers, we need to be there. It is as simple as that.

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Martian glacier with moraine?

3:03 pm

Glacier flow on Mars, with moraine

Cool image time! In the past two decades numerous images and studies of the Martian terrain produced by orbiters have shown us landslides, lava flows, water and ice produced flows, and many glacial features, all vaguely familiar but often having components reminding us of the alien nature of the Martian landscape. I have posted many here at Behind the Black. (Just do a search here for the words “Mars flow” and you will have a wealth of cool images and alien geological features to explore.)

The image on the right, rotated, cropped, and reduced to post here, shows another such feature, but this time it is less alien and more resembling a typical Earth glacier, flowing downhill slowly and pushing a moraine of debris before it. The picture was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and was part of the January image release. If you click on the image you can see the complete photograph at full resolution.

The release has no caption, but is titled “Tongue-Shaped Glacier in Centauri Montes,” referring to the largest tongue-shaped flow on the left. This feature, more than any other in the image, resembles closely many glaciers on Earth. It even has an obvious moraine at its head. As the glacial flow pushed downward slowly it gathered a pile of material that eventually began to act almost like a dam.

The location of this feature is intriguing in its own right.
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Rock from Earth, found on Moon?

2:24 pm

The uncertainty of science: Scientists studying rocks brought back by the Apollo 14 lunar mission have concluded that one sample originally came from the Earth, and if so would be the oldest known Earth rock.

It is possible that the sample is not of terrestrial origin, but instead crystallized on the Moon, however, that would require conditions never before inferred from lunar samples. It would require the sample to have formed at tremendous depths, in the lunar mantle, where very different rock compositions are anticipated. Therefore, the simplest interpretation is that the sample came from Earth.

The team’s analyses are providing additional details about the sample’s history. The rock crystallized about 20 kilometers beneath Earth’s surface 4.0-4.1 billion years ago. It was then excavated by one or more large impact events and launched into cis-lunar space. Previous work by the team showed that impacting asteroids at that time were producing craters thousands of kilometers in diameter on Earth, sufficiently large to bring material from those depths to the surface. Once the sample reached the lunar surface, it was affected by several other impact events, one of which partially melted it 3.9 billion years ago, and which probably buried it beneath the surface. The sample is therefore a relic of an intense period of bombardment that shaped the Solar System during the first billion years. After that period, the Moon was affected by smaller and less frequent impact events. The final impact event to affect this sample occurred about 26 million years ago, when an impacting asteroid hit the Moon, producing the small 340 meter-diameter Cone Crater, and excavating the sample back onto the lunar surface where astronauts collected it almost exactly 48 years ago (January 31–February 6, 1971).

The scientists also admit that their conclusion is controversial and will be disputed. If true, however, it suggests that there is significant material on the Moon from the early Earth that can provide a window into parts our planet’s history that are presently inaccessible.

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Earth’s magnetic field undergoing unexpected changes

1:25 pm

The uncertainty of science: For reasons that scientists do not understand, the Earth’s magnetic field has been undergoing unexpected shifts in the past two years, causing its north pole to move significantly and somewhat quickly from Canada across to Siberia.

Earth’s north magnetic pole has been skittering away from Canada and towards Siberia, driven by liquid iron sloshing within the planet’s core. The magnetic pole is moving so quickly that it has forced the world’s geomagnetism experts into a rare move.

On 15 January, they are set to update the World Magnetic Model, which describes the planet’s magnetic field and underlies all modern navigation, from the systems that steer ships at sea to Google Maps on smartphones.

The most recent version of the model came out in 2015 and was supposed to last until 2020 — but the magnetic field is changing so rapidly that researchers have to fix the model now. “The error is increasing all the time,” says Arnaud Chulliat, a geomagnetist at the University of Colorado Boulder and the National Oceanic and Atmospheric Administration’s (NOAA’s) National Centers for Environmental Information.

Note that they have delayed the release of the World Magnetic Model until January 30, claiming the delay is caused by the government shutdown. Seems bogus to me. As I have already noted, these scientists aren’t slaves. If they think this is so important, and they have completed their work (which the article suggests they have), they can release the model, regardless of the federal government’s funding.

Hat tip reader Stephen Taylor.

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Dried mud cracks on Mars?

3:10 pm

Mud cracks on Mars?

Cool image time! The image to the right, cropped and rotated to post here, was one of the uncaptioned photographs in the December Mars Reconnaissance Orbiter (MRO) image release. If you click on the image you can see the entire photograph. I have cropped the most interesting area, though cracks can be seen in other areas in the image.

What we appear to have here is a darker lower valley filled with dried mud, which over time has cracked as it dried. At its edges there appear to be ripples, almost like one sees on the beach as waves wash the shore. The perimeter slopes even show darker streaks as if the water in some places lapped up the slopes, and in others flowed downward into the valley.

Later, several meteorite impacts occurred, the largest of which produced concentric dried cracks on its outside perimeter. This impact also provides a rough idea of the depth of the mud in this valley.

Mud of course suggests that this lower valley once was filled with water. Was it? It is not possible now to come to a firm conclusion, but this image’s location shown by the red dot in the overview map below and to the right, provides a clue that strengthens this hypothesis.
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The lava tubes and canyons of Cerberus Fossae

3:08 pm

Cerberus Fossae rock falls

Cool image time! In the November image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO) I found the image on the right (cropped to post here), dubbed “Possible Rock Falls on Steep Slopes in Cerberus Fossae.” You can see the full image by clicking on the photo on the right.

The cropped section focuses on the steep cliffs of this deep canyon, formed when lava flowed down from the giant volcano Elysium Mons almost like water, following the faults created by the bulging volcanoes to carve a long series of parallel canyons more seven hundred miles in length. Not only can individual boulders be seen piled up on the base of the canyon, you can see on the lower right a large section of cliff that has broken off and partly fallen, propped now precariously on the cliff’s steep slope. I would not want to be hiking below it at the base of this canyon.

Elysium Mons and Cereberus Fossae

This photograph itself made me more interested in looking at other MRO images of Cerberus Fossae. The context map on the right shows that MRO has taken numerous images along the length of these faults, indicated by the red boxes. The location of the above image is shown by the white cross, at the western end where the canyons tend to be steep, deep, and pronounced. In taking a look at the many images of Cerberus Fossae, I found a variety of canyons, plus pit chains, lava tube skylights, and one especially intriguing image, posted below, that shows what appears to be an extended collapse along the length of what was once an underground lava tube.
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Present and future landing sites on Mars

11:50 am

With InSight’s landing on Mars set for 11:54 am (Pacific) this coming Monday, November 26, 2018, I decided to put together a map of Mars showing the location of all the successful landers/rovers, adding the landing sites for the planned landers/rovers through 2020. This will give some context to InSight’s landing site.

Landing sites on Mars

The map does not show the landing sites for the failed Soviet, American, and British landers.

As I noted in describing the Mars2020 landing site, the location of the bulk of these landing sites, along the transition zone from the southern highlands and the northern lowlands, demonstrates the areas of the planet that interest geologists the most. It is here that we find many shoreline features, suggestive of the ocean that many scientists theorize existed intermittently in the northern lowlands. It is here that planetary scientists can quickly gather the most information about Martian geological history. And it is here that they have the opportunity to study the widest range of rock types.

From an explorer’s perspective, however, this approach has its limits. It does not provide us a look at a wide variety of locations. It is not directly aimed at finding lower latitude locations where ice might actually exist. And it is decidedly not focused in studying the planet from the perspective of future colonists. I am sometimes frustrated that we have as yet no plans to send any rovers into Marineris Valles, or to the western slopes of Arsia Mons, the southern most volcano in the chain of three giant volcanoes where there are indications that ice might exist underground, or to any of the places where caves are known to exist where a colony could be built more easily. In fact, the caves on the slopes of Arsia Mons seems a prime exploration target.

Eventually these locations will be explored, likely by private landers aimed at scouting out locations for future private settlements. I am just impatient.

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The soft landslides of Mars

12:14 pm

A soft avalanche on Mars

Context image of landslide

The light gravity of Mars, combined with different materials, a lot of dust, and a geological history different from Earth, produces events that — though reminiscent of similar geological events on Earth — are definitely not the same.

The image above, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and was one of the many uncaptioned images released in the November archive. If you click on the image you can see the full resolution version. It shows the tongue of a landslide inside a crater located in the planet’s southern highlands.

You can immediately see why I call it a soft landslide. The craters on its top are barely visible, as if they hit a soft surface that absorbed most of the impact. The grooves spreading southward in the slide suggest that this solid material flowed almost like mud. And the soft, smooth surface head of the slide suggests an almost liquid-like flow. As far as I can tell, this landslide had few large boulders. It was made up instead of small particles of about the same size.

To the right is an image showing the wider context of the above image, taken by Mars Odyssey and cropped and annotated by me to post here. The white box shows the entire area photographed by the full resolution image of the landslide, with the tongue of the landslide at the bottom of the box. If you look at the floor of this crater, you can see what looks like the ghost of a past smaller impact, seemingly buried in either a field of lava or soft dusty regolith. The smoothness of the crater floor also suggests a material softness, allowing it to settle into a pondlike featureless flat plain.
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The fractured floor of Komarov Crater

10:35 am

Fractured floor of Komarov Crater

Cool image time! The Lunar Reconnaissance Orbiter (LRO) oblique image on the right, reduced significantly from the original to post here, shows the deeply fractured floor of Komarov Crater on the Moon’s far side. As noted at the image link,

The spectacular fractures that cut across the floor of Komarov crater [about 85 kilometers or 50 miles diameter] were formed when magma rose from the mantle, uplifting and fracturing the crater in the process. In this case the magma did not erupt to the surface, thus the fractures remain visible.

The Komarov fractures are quite large, the major left-to-right fracture that cuts across the center of the scene is over 500 meters deep [1,600 feet] and 2500 meters wide [1.5 miles]. When did they form? The large number of craters superimposed on the floor and fractures testifies to their ancient ages. Likely they are of the same vintage (>2.6 billion years) as the Mare Moscoviense lava plains just to the north

An overview of Komarov Crater as well as other LRO images of it can be found here.

The question that comes to my mind is the relative rarity of craters with such large fractures on their floors. I have noted this for Mars as well. It is expected that there is melt on the floor of all large impact craters. Why do a few produce such pronounced fractures, while most do not? This website posits one explanation, but its complexity leaves me unsatisfied. It also doesn’t explain why it happens only rarely.

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Scientists discover giant impact crater buried under Greenland ice

2:34 pm

Scientists have discovered the existence of a giant impact crater buried under the Greenland ice.

An international team of researchers, including a NASA glaciologist, has discovered a large meteorite impact crater hiding beneath more than a half-mile of ice in northwest Greenland. The crater — the first of any size found under the Greenland ice sheet — is one of the 25 largest impact craters on Earth, measuring roughly 1,000 feet deep and more than 19 miles in diameter, an area slightly larger than that inside Washington’s Capital Beltway.

They think, based on the data, that this crater is very young, one of the youngest known on Earth. At the most is is no more than 3 million years old.

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Volcanic rivers on Mars

12:53 pm

Granicus Valles

Cool image time! The photo on the right, cropped and reduced to post here, was part of the November image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO). If you click on the image you can see the full resolution picture.

The uncaptioned release webpage is dubbed “Faults in Granicus Valles.” The image itself only shows a small part of Granicus Valles, named after a river in Turkey, that flows down from the estern slopes of the giant volcano Elysium Mons. While far smaller than the four big Martian volcanoes in the Tharsis region to the east and near Marines Valles (which I highlight often), Elysium Mons still outshines anything on Earth at a height of almost 30,000 feet and a width of 150 miles. It sits at about the same northern latitude of Olympus Mons, but all by itself, rising up at the very northern edge of the transition zone between the southern highlands and the northern plains, with the vast Utopia Basin, the second deepest basin on Mars, to the west.

Overview of Elysium Mons and Granicus Valles

Granicus Valles itself is almost five hundred miles long. At its beginning it flows in a single straight fault, but once it enters the northern plains of Utopia Basin it begins to meander and break up into multiple tributaries. The MRO image above shows only a tiny portion in the northern plains, as illustrated by the white box in the overview map to the left.
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