Tag: geology

Mars’ seasonally vanishing carbon dioxide polar cap

1:36 pm

Buzzell dunes, March 19, 2019
Click for full image.

Since the onset of the Martian spring in the northern hemisphere back in March of this year, scientists have been busy using the high resolution camera on Mars Reconnaissance Orbiter (MRO) to monitor the expected sublimation and disappearance of the cap of dry ice that falls as snow to become a winter layer mantling both the more permanent icecap of water 7,000 feet deep as well as the giant dune sand seas that surround that northern icecap.

The image on the right was first posted here on Behind the Black on June 6, 2019 as part of a long article describing that northern polar icecap and its annual evolution. It shows a set of dunes that Candice Hansen of the Planetary Science Institute in Arizona, who requested the image, has dubbed “Buzzell.” When that picture was taken in March, the frozen dry ice layer of translucent carbon dioxide still coated the dunes. The image’s darkness is because the Sun has just begun to rise above the horizon at this very high latitude location (84 degrees). The circular feature is likely a buried ancient crater, with the streaks indicating the prevailing wind direction blowing both sand and frost about.

On August 9, 2019 I provided an update on this monitoring, when new images of this same location were downloaded from MRO in April and June. MRO has now taken a new image of Buzzell, on October 2, 2019. Below the fold are all these images so that you can see the sublimation and disappearance of that dry ice layer over time.
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Rover update: October 28, 2019

1:05 pm

Summary: Curiosity finally on the move after several months drilling two adjacent holes in the clay unit. Yutu-2 continues roving west, has it now operates during its eleventh lunar day on the far side of the Moon.

For the updates in 2018 go here. For a full list of updates before February 8, 2018, go here.

Curiosity's present location in Gale Crater
Click for original full image.

Curiosity

For the overall context of Curiosity’s travels, see my March 2016 post, Pinpointing Curiosity’s location in Gale Crater.

I have not done any of my regular rover updates since May 30, 2019 because it was simpler to do individual updates for both Curiosity and Yutu-2, the only working rovers presently on other worlds. (If things had gone well, which they did not, we would have had two other lunar rovers in the past six months, one from Israel and one from India, but both crashed during landing.)

However, since Curiosity is finally on the move after spending several months at one location, where it drilled two holes in the clay unit (the material from one used in a wet cup experiment to look for organic life) it is time to update my readers on where Curiosity is and where it is heading.

The first image above and to the right is an annotated overview of Curiosity’s present position, moving south to a line of buttes which scientists have determined delineates the transition from the clay unit to a new geological layer they have dubbed the Greenheugh Pedimont. The yellow lines indicate the area seen in the panorama below, created from two photographs (here and here) taken by the rover’s navigation camera.
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NASA to send new rover to lunar south pole

2:36 pm

NASA today announced that it is building a lunar rover that it will send to the lunar south pole, with a target launch date of December 2022.

About the size of a golf cart, the Volatiles Investigating Polar Exploration Rover, or VIPER, will roam several miles, using its four science instruments — including a 1-meter drill — to sample various soil environments. Planned for delivery to the lunar surface in December 2022, VIPER will collect about 100 days of data that will be used to inform the first global water resource maps of the Moon.

This rover appears to be a traditional NASA project, designed, built, and managed by various NASA agencies that also subcontract the work out to private contractors. As the press release says,

VIPER is a collaboration within and beyond the agency. VIPER is part of the Lunar Discovery and Exploration Program managed by the Science Mission Directorate at NASA Headquarters. Ames is managing the rover project, leading the mission’s science, systems engineering, real-time rover surface operations and software development. The hardware for the rover is being designed by the Johnson Space Center, while the instruments are provided by Ames, Kennedy, and commercial partner, Honeybee Robotics. The spacecraft lander and launch vehicle that will deliver VIPER to the surface of the Moon, will be provided through NASA’s Commercial Lunar Payload Services (CLPS) contract, delivering science and technology payloads to and near the Moon. [emphasis mine]

The highlighted words however indicate where this project differs from the past. The launch vehicle and lander are not being designed and built by NASA. They will be provided by commercial vendors.

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Ancient glacier flows on Mars

3:17 pm

Ancient glacial flow in Euripus Mons
Click for full image.

Cool image time! In the recent download of images from the high resolution camera of Mars Reconnaissance Orbiter (MRO), I found the image on the right, rotated, cropped, and reduced to post here. It shows an example of the many glacial flows coming off of the slopes of Euripus Mons, the sixteenth highest mountain on Mars.

We know these are glaciers because data from SHARAD, the ground-penetrating radar instrument MRO, has found significant clean ice below the surface, protected by a debris layer that insulates it. As planetary scientist Alfred McEwen of the Lunar & Planetary Laboratory in Arizona explained to me in a phone interview yesterday,

These are remnant glaciers. Basically they form like glaciers form. They are not active or if they are they are moving so extremely slowly that effectively they are not active.

If you look close, you can see that this particular glacier was made up of multiple flows, with the heads or moraines of each piled up where each flow ended. In addition, this overall glacier appears to have been a major conduit off the mountain, following a gap between more resistant ridges to the east and west.

The sequence of moraines suggest that when the glacier was active, it experienced alternating periods of growth and retreat, with the growth periods being shorter and shorter with time. As a result each new moraine was pushed less distance down the mountain as the previous one.

Euripus Mons is interesting in that it has a very large and distinct apron of material surrounding it, as shown in the overview image below.
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Curiosity takes selfie next to two of its most important drill holes

3:04 pm

Curiosity and its most recent drill holes
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The Curiosity science team today released a beautiful mosaic of the rover, stitched from 57 different images. The photo at the right, cropped and reduced to post here, is the annotated version of that image. It shows the rover’s two most recent drill holes to the left. As the view looks away from Mount Sharp, you can see in the distance Vera Rubin Ridge, the floor of the crater, and its rim on the far horizon.

The two drill holes are significant because of the chemical experiment that Curiosity is subjecting the material from those holes.

The special chemistry experiment occurred on Sept. 24, 2019, after the rover placed the powderized sample from Glen Etive 2 into SAM. The portable lab contains 74 small cups used for testing samples. Most of the cups function as miniature ovens that heat the samples; SAM then “sniffs” the gases that bake off, looking for chemicals that hold clues about the Martian environment billions of years ago, when the planet was friendlier to microbial life.

But nine of SAM’s 74 cups are filled with solvents the rover can use for special “wet chemistry” experiments. These chemicals make it easier for SAM to detect certain carbon-based molecules important to the formation of life, called organic compounds.

Because there’s a limited number of wet-chemistry cups, the science team has been saving them for just the right conditions. In fact, the experiment at Glen Etive is only the second time Curiosity has performed wet chemistry since touching down on Mars in August 2012.

This time however was the first time they had used a wet chemistry cup on material from a drill hole. That they were able to do this at all is a testament to the brilliant innovative skills of the rover’s engineers. They had been holding off doing a wet chemistry analysis from drill hole material until they got to this point, but on the way the rover’s drill feed mechanism failed. It took more than a year of tests and experimentation before they figured out a way to bypass the feed mechanism by using the arm itself to push the drill bit into the ground. That rescue made possible the wet chemistry experiment that they initiated on September 24.

The results, which are eagerly awaited, won’t be available until next year, as it will take time for the scientists to analyze and publish their results.

Curiosity meanwhile has moved on, leaving this location where it had remained for several months to march in the past week southward back towards its long planned route up Mount Sharp.

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Big landslides on Mars might not require ice

1:49 pm

According to a new paper, scientists now think the biggest and longest landslides found on Mars might not require a base of ice on which it could slide such extensive distances.

The findings, published today in Nature Communications, show for the first time that the unique structures on Martian landslides from mountains several kilometres high could have formed at high speeds of up to 360 kilometres per hour due to underlying layers of unstable, fragmented rocks.

This challenges the idea that underlying layers of slippery ice can only explain such long vast ridges, which are found on landslides throughout the Solar System.

First author, PhD student Giulia Magnarini (UCL Earth Sciences), said: “Landslides on Earth, particularly those on top of glaciers, have been studied by scientists as a proxy for those on Mars because they show similarly shaped ridges and furrows, inferring that Martian landslides also depended on an icy substrate. “However, we’ve shown that ice is not a prerequisite for such geological structures on Mars, which can form on rough, rocky surfaces. This helps us better understand the shaping of Martian landscapes and has implications for how landslides form on other planetary bodies including Earth and the Moon.”

The lighter gravity of Mars, about one third of Earth’s, is part of the explanation, though many other factors are involved. Either way, this is one more data point in the evidence that the though geology on Mars might look like what we see on Earth, it is likely very different than we expect, due to the alien nature of Mars itself.

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Bhabha Crater at dawn

9:53 am

Central peaks of Bhabha Crater at dawn

Cool image time! The Lunar Reconnaissance Orbiter (LRO) science team have released a beautiful oblique image of Bhabha Crater, located on the Moon’s far side, taken just as dawn was breaking over the crater’s central peaks.

The image to the right is a section of that picture, showing the central peaks near the bottom with the western rim of the 50-mile-wide crater at the top. The giant shadows of those central peaks can be seen extending across the floor of the crater and against that western rim. The photograph was taken on August 28, 2019 from an altitude of about 45 miles. The area of the central peaks in daylight is estimated to be about nine miles across.

The LRO science team releases a new press release image about once every two weeks. I suspect that they hoped this release would have shown the location of India’s Vikram lander. As they are as yet unable to find it, they instead provided us this cool image instead.

If you go to the link you can use their viewer to view and explore this very very large image. For example, if you zoom into those central peaks you can actually see small boulders scattered across their rounded tops.

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Chang’e-4 and Yutu-2 awake for 11th lunar day

9:13 am

Engineers have reactivated both Chang’e-4 and Yutu-2 to begin normal operations on their eleventh lunar day on the far side of the Moon.

As is usual for these reports from the state-run official media in China, the article provides little information. However, this article today from space.com provides an update on the “gel-like” material that Yutu-2 spotted in August.

While gaining the attention of the Yutu 2 team, the material does not appear altogether mysterious, as claimed by Chinese media.

Clive Neal, a lunar scientist at the University of Notre Dame in Indiana, told Space.com that the new image reinforces the previous suggestion that the material is broadly similar in nature to a sample of impact glass found during the Apollo 17 mission in 1972.

…Dan Moriarty, NASA Postdoctoral Program fellow at the Goddard Space Flight Center in Greenbelt, Maryland, has analyzed and processed the image, seeking clues as to its precise nature. While this compressed image lacks a lot of the useful information a raw image would contain, Moriarty said he could gain insights by adjusting parameters. “The shape of the fragments appears fairly similar to other materials in the area. What this tells us is that this material has a similar history as the surrounding material,” Moriarty said. “It was broken up and fractured by impacts on the lunar surface, just like the surrounding soil.

Overall, Yutu-2 has traveled about 950 feet or 290 meters westward from Chang’e-4 since it began roving at the start of the year.

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InSight’s digging problems reveal the alienness of Mars’ soil

9:01 am

Even as InSight’s mole shaft driller shows signs of working, its difficulties in digging into the Martian soil has revealed how truly alien that soil is from what we normally expect.

[U]nlike typical holes dug here on Earth, the one excavated by InSight’s mole has no lip of dirt around its rim, Hoffman said. “Where did the soil go?” he said. “Basically, it got pounded back into the ground, so it seems like it’s very cohesive, even though it’s very dusty.”

And this is a weird combination of characteristics, strongly suggesting that Mars dirt is alien in more ways than one. “The soil properties are very different than anything we’ve ever seen on Earth, which is already a very interesting result,” Hoffman said.

That the soil of Mars is alien should not be a surprise. The planet’s dusty nature, combined with its light gravity and lack of life, practically guaranteed that the soil would have different and unexpected properties. What is disturbing is that it appears this likelihood was not considered in the slightest by the German engineers who designed the mole for digging.

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Lava-draped terrain on Mars

1:58 pm

Lava surrounding hill and partly covering crater
Click for full image.

Hill surrounded by lava flows
Click for full image.

Cool image time! Continuing this week’s series of lava-related images from Mars (previous posts here, here, and here), today’s post is ironically the first to actually show lava flows.

The two images to the right, reduced and cropped to post here, are sections taken from an uncaptioned picture, titled “Lava-Draped Surface in Cerberus Palus” and found in the most recent download from the high resolution camera on Mars Reconnaissance Orbiter (MRO).

It is obvious why the MRO scientists gave this image this title. The hills in both pictures clearly seem to stand up like islands in a surrounding sea of frozen lava. Older craters, created prior to the lava flow, are partly obscured by the lava flows, their interior floors filled and their rims broken as the lava flooded this region.

Nor are these the only high points captured in the image that this flood of lava inundated. If you look at the full image there is even a low mound where it appears the surrounding lava flood worked its way up the hill’s gently sloping flanks only to freeze just before it completely covered the top of the mound.

The location of this image, shown by the red box in the overview map below and to the right, gives us a hint where the lava came from, though the distances involved to the nearest giant volcano, Elysium Mons, are so large it is likely that this flow is not directly linked to that volcano.
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Sinkholes on Mars

2:01 pm

Collapse pit on Mars
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Cool image time! In this week’s exploration of Martian geology that is reminiscent of Earth-based lava geology, today’s image is of a collapse pit in Ceraunius Fossae, the vast region of north-south fissures found to the south of the volcano Alba Mons. The photo to the right, cropped to post here, zooms in on that pit.

The picture was part of the most recent image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO). What makes it especially interesting is the sharpness of its rim, in comparison to the collapse channel to the east. This suggests the pit is younger and fresher than the channel, and happened more recently. This also implies that the voids below the ground in which the surface is sinking are either still there, or due to on-going processes might be still be forming (like caves are on Earth).

For example, if there is underground ice, temperature changes or even thermal heat from the nearby giant volcanoes could melt that underground ice periodically, allowing it to flow and erode the surrounding material, forming voids. That this pit is located at 30 degrees north latitude, just inside the northern hemisphere band where glaciers are found, adds weight to this possibility.

The image below, reduced and rotated so that north is to the left, shows the entire sequence of collapse channels, with the more distinct pit from above in the bottom center of the picture.
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A discontinuous Martian channel

12:57 pm

Discontinuous channel near Olympica Fossae
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Close-up of channel

Time for more strange Martian geology! As I said in my post yesterday of a cool image of skylights into what might be a Martian lava tube, this is lava week on Behind the Black. The image at the right, rotated, reduced, and cropped to post here, is similar to yesterday’s photograph, showing a line of sinks and depressions that strongly suggest the existence of an underground lava tube.

The problem with this theory is that at present we really have no idea what flowed here. It could have been lava, but it also could have been mud, water, ice, or some as yet unimagined Martian geological process.

The image was part of the most recent image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO), and was uncaptioned. The top image shows the whole channel as captured by the photograph, with the white box indicating the area covered by the second image, posted here at full resolution.

Though the overall slope of the terrain here is downhill to the west, the grade is relatively shallow, so there is no guarantee that the local slope of this particular channel follows that trend. Downhill could be either to the west or the east.

The reason I favor lava (as an amateur geologist) is the location of this channel, as shown in the overview map below and to the right.
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Skylights into Martian lava tube?

12:31 pm

Possibly connected skylights into lava tube
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Close-up of skylights
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Cool image time! In the archive of images from the high resolution camera on Mars Reconnaissance Orbiter (MRO) I came across the uncaptioned image on the right, dubbed “Possibly Connected Lava Tube Skylight Pair in Tharsis Region.”

The top image, cropped and reduced to post here, is a wide view, showing a narrow depression oriented in a north-south direction. Downhill is to the north, with the caldera of the giant volcano Arsia Mons to the south. The white box indicates the area covered by the bottom image, cropped and expanded to post here. Within this close-up are two dark spots, each about 150 feet across.

The two dark spots surely look like small pit openings. Their alignment with the north-south depression strongly suggests that an underground lava tube is below. That this depression is also aligned with the downhill slope further reinforces this supposition.

The depression itself also aligns with the gigantic fault that runs from the northeast to the southwest through all three of the giant Tharsis Bulge volcanoes. Arsia Mons is the southernmost of the three. It is also where that fault is most clearly expressed by two dramatic breaks in the volcano’s rim in the northeast and southwest, as seen in the overview image below. Scientists have taken of lot of images of these breaks in an effort to better understand the geology and how it fits in with the formation of the volcanoes.

Overview of Arsia Mons

However, a review of the entire image archive of MRO’s high resolution camera shows that scientists have taken very few close-up images in this region. The black box in the overview map on the right is the location of this image. As of now, only three other high resolution images, as indicated by the white boxes, have been taken by MRO of this part of the volcano’s north slope.

That the skylights and depression align with this giant fault is not evidence that this supposed lava tube is linked to that fault. Lava will flow down the mountain’s slopes, fault or no fault. At the same time, the fault’s existence is also going to encourage north-south cracks and fissures, which in turn could have served as a convenient flow route for the lava. Without a closer look, on site, it is hard to know one way or the other..

I’ve located a few more lava related cool images in the MRO archive, so I’m going to make this week lava week on Behind the Black. Stay tuned!

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Ice! Ice! Everywhere on Mars ice!

1:20 pm

Ice scarp in Milankovic Crater
Click for full image.

In January 2018 scientists announced the discovery of exposed ice in a number scarp cliff faces found in the high-mid-latitudes of Mars.

These scarps, which have so far been found in one southern 50-55 degree latitude strip and in one crater, Milankovic, at the same latitude in the north, are important because they are one of the first places on Mars in its lower latitudes where we have found ice actually exposed and visible, not buried like the many buried glaciers very near the surface found in the 30 to 60 degree northern and southern latitude bands.

Since that press announcement, scientists have been monitoring these sites for changes, as well as expanding their survey to see if they can locate more of these scarps.

Overview map

My previous posts on this subject were mostly focused on that southern strip near Hellas Basin, as shown on the map on the right. In reviewing the most recent image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO), I noticed that the only new images of ice scarps were taken in the northern location, in Milankovic Crater, as indicated by the white dot north of Olympus Mons. The first image above shows the north-facing scarp of one of these images, cropped to focus in on the color section where, if you look close, you will see a strip of blue across the base of the scarp. That’s the ice layer, exposed as the scarp sublimates away over time from the north to the south.

over view of all MRO images taken so far in Milankovic Crater

This scarp, labeled #2 on the overview map of Milankovic Crater on the right, is located inside the crater’s eastern rim. The second image, posted below and labeled #1 on the overview map, shows a wider area of several ice scarps located on the inside of the crater’s southwestern rim.

The red boxes in the overview map indicate all the images taken by MRO inside this crater. If you go to the camera’s archive and focus in on Milankovic Crater at 54.5 degrees north latitude and 213.3 degrees longitude, you can then click on each red box to see the high resolution image. In practically every image along the crater’s inside rim can be found numerous scarps.
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Swirls and layers in Martian depression

12:42 pm

Close-up on swirls and layers

Context of depressions in Columbus Crater
Click for full resolution image.

Cool image time! The southern highlands of Mars is littered with numerous craters, making it look from a distance not unlike the Moon. A closer inspection of each crater and feature, however has consistently revealed a much more complex history than seen on the Moon, with the origins of many features often difficult to explain.

The two images on the right, rotated, cropped, and reduced to post here, shows one such feature in the floor of one southern highlands crater, dubbed Columbus Crater. The top image is a close-up of the area shown by the box in the bottom image.

The uncaptioned full photograph was taken on May 20, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and was simply titled “Depression in Columbus Crater.” Since the photo included two large depressions, as shown in the wider view in the bottom image, I’m not sure which depression this title refers. In both cases the features do not appear to be impact craters. The top depression is far too irregular, while both do not have the upraised rims that are found on most impact craters.

I have zoomed into the top depression because of its many swirls and layers. On Earth such terrain is usually caused by either water or wind erosion, slowly carving a smooth path across multiple geological layers. Here, there is no obvious evidence of any flows in any direction. Something ate out the material in this depression, exposing the many layers, but what is not clear.

The lower depression reminds me of sinkholes on Earth, where the ground is subsiding into a void below ground The same process could have also formed the top depression.

The surrounding terrain is equally baffling, resembling the eroded surface of an ice block that has been sprayed with warm water. In fact, the entire floor of Columbus Crater appears to have intrigued planetary scientists, as they have requested a lot of images of it from MRO. So far they do not have enough of these images to produce a full map. Since the terrain appears to change drastically over short distances, it is therefore hard to fit the geology of each image together. The overall context is missing.

When I first saw this image I tried to reach the scientist who requested it in the hope he might provide me a more nuanced explanation of what we see here, but despite repeated requests he never responded. Therefore let me propose one theory, based on my limited knowledge of Martian geology.
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The drying out of Mars

10:05 am

Edge of wash
The Murray formation as seen in 2017

A new paper based on data gathered by the rover Curiosity in 2017 when it was lower on the slopes of Mount Sharp, as well as data obtained more recently at higher elevations, has confirmed that the past Martian environment of Gale Crater was wetter, and that deeper lakes formed lower down, as one would expect.

In 2017 Curiosity was traveling through a geological layer dubbed the Murray formation. It has since climbed upward through the hematite formation forming a ridge the scientists dubbed Vera Rubin Ridge to reach the clay formation, where the rover presently sits. Above it lies the sulfate-bearing unit, where the terrain begins to be get steeper with many very dramatic geological formations.

Looking across the entirety of Curiosity’s journey, which began in 2012, the science team sees a cycle of wet to dry across long timescales on Mars. “As we climb Mount Sharp, we see an overall trend from a wet landscape to a drier one,” said Curiosity Project Scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory in Pasadena, California. JPL leads the Mars Science Laboratory mission that Curiosity is a part of. “But that trend didn’t necessarily occur in a linear fashion. More likely, it was messy, including drier periods, like what we’re seeing at Sutton Island, followed by wetter periods, like what we’re seeing in the ‘clay-bearing unit’ that Curiosity is exploring today.”

Up until now, the rover has encountered lots of flat sediment layers that had been gently deposited at the bottom of a lake [the Murray Formation]. Team member Chris Fedo, who specializes in the study of sedimentary layers at the University of Tennessee, noted that Curiosity is currently running across large rock structures [Vera Rubin Ridge and the clay formation] that could have formed only in a higher-energy environment such as a windswept area or flowing streams.

Wind or flowing water piles sediment into layers that gradually incline. When they harden into rock, they become large structures similar to “Teal Ridge,” which Curiosity investigated this past summer [in the clay formation]. “Finding inclined layers represents a major change, where the landscape isn’t completely underwater anymore,” said Fedo. “We may have left the era of deep lakes behind.”

Curiosity has already spied more inclined layers in the distant sulfate-bearing unit. The science team plans to drive there in the next couple years and investigate its many rock structures. If they formed in drier conditions that persisted for a long period, that might mean that the clay-bearing unit represents an in-between stage – a gateway to a different era in Gale Crater’s watery history.

None of these results are really surprising. You would expect lakes in the flatter lower elevations and high-energy streams and flows in the steeper higher elevations. Confirming this geology however is a big deal, especially because they are beginning to map out in detail the nature of these geological processes on Mars, an alien world with a different make-up and gravity from Earth.

Below the fold is the Curiosity science teams overall map, released in May 2019, showing the rover’s future route up to that sulfate unit, with additional annotations by me and reduced to post here.
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Weird glacial features in Martian crater

1:47 pm

weird glacial feature in crater on Mars
Click for full image.

Cool image time! In reviewing today’s October release of new images from the high resolution camera of Mars Reconnaissance Orbiter (MRO), I came across the strange geology shown in the image to the right, rotated, cropped, and reduced to post here.

The uncaptioned image calls these “glacial features within crater.” The crater is located at 35 degrees north latitude in Arabia Terra, one of the more extensive regions of the transition zone between the northern lowlands and the southern highlands. It is also located within the northern band from 30 to 60 degrees latitude where most of the buried Martian glaciers are found.

The most abundant type of buried glaciers are called concentric crater fill (CCF) because they are found inside craters, and often show decay in a concentric manner. This weird feature likely falls into that category, though I would hardly call these glacier features concentric.

I’m not even sure if this is an impact crater. If it is, its rim has been heavily obscured, making it look instead like an irregular depression with one outlet to the south. In fact, I suspect it is possibly one of the lakes that scientists believe pepper this part of Arabia Terra and might have contained liquid water two to three billion years ago. That water would have later frozen, and possibly become covered by dust and debris to protect it.

According to present theories, Mars is presently in a period where its mid-latitude glaciers are shrinking, the water sublimating away and being transported back to its poles. The weird formations here suggest this process. Imagine what happens when you spray warm water on a big block of ice. It dissolves, but randomly to form weird shapes.

In this case the glacier is shrinking randomly where the ice has gotten exposed. In the thin Martian atmosphere, it transitions directly from a solid to a gas, sublimating into the atmosphere to leave these inexplicable shapes.

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The slowly changing dunes of Mars

1:15 pm

Map of Mars

In order to better understand the climate and geology of Mars, scientists need to study how the thin Martian atmosphere causes changes to the planet’s numerous sand dunes. To do this, they have been using the high resolution camera on Mars Reconnaissance Orbiter (MRO) to periodically snap photos of the same places repeatedly over time, to track any changes that might occur.

Recently the monthly download dump of images from MRO included one such location in the northwest quadrant of Hellas Basin, what I call the basement of Mars because it the planet’s lowest point. The uncaptioned image was taken on May 20, 2019 and was titled “Hellas Region Sand Dune Changes.” A review of past images shows that MRO has taken pictures of this location several times in the past, in 2011 and in 2017. All these images were taken during the Martian autumn season, and were taken to see if over time there were any significant changes to the dunes due to winds.

My superficial comparison of the 2011 and 2017 images does not show much obvious change. There could be small changes that my quick review did not spot, and there is also the strong possibility that the entire dune field could have shifted as a unit over those three Martian years, a change that would require a more detailed analysis beyond my technical capabilities. Click on both links, put the photographs in separate tabs, and switch quickly between them to see if you can spot any differences.

Comparing the 2011 and 2019 images however shows some significant changes, most of which I think are due to the 2018 global dust storm. Below is that comparison.
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Martian impact into lava crust?

1:13 pm

Impact crater north of Pavonis Mons
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Cool image time! The photo on the right, cropped to post here, was taken by the high resolution camera on April 23, 2019. It shows a quite intriguing impact crater on the northern lava slopes of Pavonis Mons, the middle volcano in the chain of three gigantic volcanoes to the west of Valles Marineris.

What makes this image cool is what the impact did when it hit. Note the circular depression just outside the crater’s rim. In the southeast quadrant that ring also includes a number of additional parallel and concentric depressions. Beyond the depression ground appears mottled, almost like splashed mud.

What could have caused this circular depression? Our first clue comes from the crater’s location, as shown in the overview map below and to the right.
» Read more

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Cave pits in the Martian northern lowlands

1:22 pm

New pits in Hephaestus Planitia

I could call this my monthly Martian Pit update. Since November 2018 I have each month found from two to five new and interesting cave pits in the monthly download of new images from the high resolution camera on Mars Reconnaissance Orbiter (MRO). My previous posts:

All except the last August 12 post were for pits on the flanks of Arsia Mons, the southernmost in the line of three giant volcanoes to the southeast of Olympus Mons, and were thus almost certainly resulting from lava flows.

The August 12 post instead showed pits found in Utopia Planitia, one of the large plains that comprise the Martian northern lowlands where scientists think an intermittent ocean might have once existed. All of these pits are found in a region of meandering canyons dubbed Hephaestus Fossae.

In the most recent MRO release scientists once again focused on the pits in or near Hephaetus, imaging four pits, two of which have been imaged previously, as shown in my August post and labeled #2 and #4 in this article, and two (here and here) that appear new. The image on the right, cropped to post here, shows the two new pits, dubbed #1 and #3. In the full image of #1, it is clear that this pit lines up nicely with some other less prominent depressions, suggesting an underground cave. Pit #3 however is more puzzling. In the full image, this pit actually runs perpendicular to a long depression to the west. There are also no other related features around it.

What makes all four of these pits intriguing is their relationship to Hephaestus Fossae and a neighboring rill-like canyon dubbed Hebrus Valles, as shown in the overview map below.
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Avalanche season at the Martian north pole

3:22 pm

Avalanche on-going at the edge of Mars' north pole icecap
Click for full resolution image.

As the Martian spring started to unfold in April 2019, the focus of many Martian planetary scientists immediately shifted to the northern polar icecap, where they fully expected, based on previous experience, some spectacular events to occur.

I have already reported on this year’s initial observations of the sublimation of the carbon dioxide frost layer. That frost layer, generally less than six feet thick, falls as dry ice snow with the coming of winter, then sublimates away each spring. Since the arrival of Mars Reconnaissance Orbiter (MRO) in 2006 and its discovery of this process by its high resolution camera, these scientists have been monitoring the disappearance of that frost layer from Martian year to Martian year.

That sublimation process also brings with it other spectacular changes, including the coming of frequent avalanches along the high cliff scarps, ranging in heights from 1,500 to 3,000 feet, that comprise the edge of that north pole icecap. The image above, reduced to post here, shows one of the many avalanches found this spring and photographed as they were actually happening. It looks down at the cliff that runs from the left to the lower right of the image, with its top being the flat plateau in the lower left. From the caption, written by Dr. Candice Hansen of the Planetary Science Institute in Tucson, Arizona,

Every spring the sun shines on the side of the stack of layers at the North Pole of Mars known as the north polar layered deposits. The warmth destabilizes the ice and blocks break loose.

When they reach the bottom of the more than 500 meter tall cliff face [about 1,600 feet], the blocks kick up a cloud of dust. (In the cutout, the top layer of the north polar cap is to the lower left.) The layers beneath are different colors and textures depending on the amount of dust mixed with ice.

The linear many-layered look of that cliff face is due to the many layers believed to exist within the permanent water icecap of Mars. To give some perspective, this cliff is several hundred feet taller than the World Trade Center after completion. Those falling blocks are dropping farther than the bodies that horribly fell from the Trade Center the day it was hit by airplanes flown by Islamic terrorists on September 11, 2001.

The map below shows most of the eastern half of that icecap, with the white boxes showing the various places MRO has spotted such avalanches.
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Terraced and banded hills on Mars

1:13 pm

Banded or terraced hills in eastern Hellas
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Cool image time! In my review of the most recent download of images from Mars Reconnaissance Orbiter’s (MRO) the high resolution camera, I found a very startling (and cool) image of some dramatic terraced Martian hills, taken on July 30, 2019. I wanted to post it here, but decided to first do some more digging, and found that an earlier image, taken in 2017, showed more of this particular hill. It is this earlier image posted to the right, cropped and reduced.

Don’t ask me to explain the geology that caused this hill to look as it does. I can provide some basic knowledge, but the details and better theories will have to come from the scientists who are studying this feature (who unfortunately did not respond to my request for further information).

What I can do is lay out what is known about this location, as indicated by the red box in the overview map below and to the right, and let my readers come up with their own theories. The odds of anyone being right might not be great, but it will be fun for everyone to speculate.
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Mars’ mysterious slope streaks become even more mysterious

10:10 am

Bright slope streaks in Arabia Terra
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Mars is an alien planet. This fact needs to be restated over and over, because we humans have an uncontrolled and unconscious tendency to view the things we find on Mars and assume they are caused by and resemble phenomenon we see all the time here on Earth.

Not. Mars has a very different climate, a significantly weaker gravitational field (about one third of Earth’s), and a geological and environmental make-up very alien from Earth’s. While many phenomenon there might have parallels on Earth, it is very dangerous to assume they are the same, because more often than not, they are exceedingly dissimilar and mysterious.

The image on the right is another example of this, reduced and cropped to post here. It is of some slope streaks in the Arabia Terra region on Mars, the largest most extensive region in the transition zone between the northern lowland plains and the southern highlands. I found it in my review of the August 30th release of new images from the high resolution camera on Mars Reconnaissance Orbiter.

As I already noted in my previous article about the mysterious slope streaks of Mars:

The bottom line, as noted in one paper, “The processes that form slope streaks remain obscure. No proposed mechanism readily accounts for all of their observed characteristics and peculiarities.”

Mars is strange. Mars is alien. Mars epitomizes the universe in all its glory.

The image above only reinforces this conclusion.
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Cliff collapse on Mars

2:38 pm

Cliff collapse on Mars
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Cool image time! The photograph to the left, rotated, cropped, and reduced to post here, was found in the August image release of the high resolution camera on Mars Reconnaissance Orbiter (MRO).

This was an uncaptioned image, with a title “Cataract and Grooves in Kasei Valles.” Kasei Valles is the giant canyon north of Marineris Valles. Though it is not as well known or maybe as dramatic, it is about as long and vast as its more famous southern canyon. It also has some very intriguing features, including what I consider to so far be the pit on Mars with the highest priority for exploration.

The image on the right shows the result when a giant section of this cliff face broke off and collapsed into the canyon. It also shows that the collapse occurred a long time ago. Not only are there newer craters on the collapse debris, the breakdown at the cliff base looks well eroded, as if many eons have passed since it piled up there.

When this section broke off however it was a very big event. The width of the collapse is about a mile across, with its depth about 600 feet. The height of the cliff is approximately 3000 feet, give or take a few hundred feet. Thus the chunk that broke off was about 600 feet wide, 5,000 feet long, and about 3,000 feet high. That’s one very big rock.

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Melting rocks on Mars

2:28 pm

Melt pools near Mohave Crater
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Cool image time! The image to the right, reduced, cropped, and annotated by me to post here, was part of the July image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO) and was titled “Melt Pools around Mojave Crater”.

You can see that the flow began to the south, flowed northward (in the middle of the image), and then pooled in the two places as indicated. In the full photograph you can also see that the flow continued to the north, forming more pools.

The title to me suggests that this flow and the melt pools were lava, not ice. The low latitude, 7 degrees north, also suggests this is not ice. Though I was unable to reach the person who requested these images, it appears his research is aimed understanding the melt events that occur in the vicinity of craters upon impact. From his website:
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An eroding Martian glacier?

1:11 pm

An eroded glacier on Mars?

Close-up of an eroded glacier on Mars?
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Cool image time! In my never-ending review of new images downloaded each month from the high resolution camera of Mars Reconnaissance Orbiter (MRO), I came upon an image dubbed merely “Terrain Sample” in the August release. To the right, cropped and rotated to post here, is the weird terrain from that image, with the section in the white box shown below at full resolution.

To keep MRO functioning properly, they need to take images on a regular basis, even if they have no planned features coming into view. As noted by Singleton Thibodeaux-Yost, the HiRISE Targeting Specialist at the University of Arizona who requested this image,

It was not taken in response to a suggestion from the public or our team database. This image was a ride-along with another instrument on MRO. [The scientists for that other instrument] targeted this region for a particular reason and we just turned on our camera as well to gather more data while they collected their data. I title these types of images “terrain sample” as we don’t always know what the results will be.

In other words, the scientists running the high resolution camera have no inkling what they will see until see it.

This image shows the inside rim of a crater, with the crater rim to the south just beyond the image’s bottom edge. This somewhat large crater is located in the middle of Arabia Terra, one of the largest regions of the transition zone between the southern highlands and the northern lowlands (where some scientists believe an intermittent ocean might have once existed). This transition zone has many features that suggest a tidal basin on the edge of that ocean.

A few months ago I would have been entirely baffled by what we see here. I might have speculated that these strange features were another variation of that shoreline region. Maybe these features are the erosion one sees on a dried lakebed after the water has drained away.

I might have also speculated that these shapes looked like the kind of frozen ice blocks one sees in the icecap of the Arctic here on Earth.

Both speculations then would have been complete guesses.

I now know, based on things I have recently learned in writing about several other images from MRO, that the second guess is likely right (though of course my opinion as a very amateur planetary geologist should not be taken very seriously). My reasons?
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Monitoring Martian pits not near Arsia Mons

2:59 pm

Second look at Hephaestus Fossae pit
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In reviewing the August image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO), I came upon two different new pit images, the more interesting of which is highlighted on the right, cropped to post here..

Finding new pit images from MRO isn’t surprising, since the spacecraft has been photographing pits almost monthly since November (see: November 12, 2018, January 30, 2019, February 22, 2019, April 2, 2019, May 7, 2019, and July 1, 2019).

What makes these two new pit images more intriguing are their location, and the fact that both pits were previously photographed by MRO and posted on Behind the Black on June 5, 2018 and July 24, 2018. Both are located in Hephaestus Fossae, a region of fissures on the edge of the great Martian northern lowlands to the west of the great volcano Elysium Mons.

Almost all the pits from past MRO images have been found on the slopes of Arsia Mons, the southernmost of the three giant volcanoes southeast of Olympus Mons. In fact, last month I even asked the question, “Why so many pits there, and so few pits elsewhere?” The explanation from Chris Okubo of the U.S. Geological Survey, who is requesting these images, was that maybe it was due to geology, or maybe it was because we simply do not yet have enough information and might not have identified the many caves/pits elsewhere.

It appears that this same question had already been on the minds of Okubo and his partner, Glen Cushing, also of the USGS. As Okubo wrote me when I asked him about these new images:
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Watching the yearly vanishing of Mars’ north pole dry icecap

12:45 pm

Buzzell dunes, March 19, 2019
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Buzzel dunes, April 4, 2019
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Buzzell dunes, June 4, 2019
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For the northern hemisphere of Mars it is presently spring. The season began sometime in April 2019 and will last until about October, twice as long as on Earth because of the Martian year is twice as long.

During the fall and winter the permanent water-icecap, which forms the bulk of the Martian icecap, gets covered by a mantle of dry ice, settling there as a layer of carbon dioxide snow about six feet thick. With the arrival of spring that dry icecap slowly begins sublimate away entirely.

Using the high resolution camera on Mars Reconnaissance Orbiter (MRO) planetary scientists are monitoring this process, taking pictures periodically.

On June 6, 2019 I had written a detailed story describing the Martian North Pole and outlining the process by which this sublimation of the dry icecap mantle takes place.

When winter ends and the sun reappears at this Arctic location, a small percentage of that sunlight, about 10%, goes through the dry ice and warms the sand that the dry ice mantles. This in turn warms the bottom of the dry ice layer, causing this to sublimate into a gas that is now trapped.

When the pressure builds sufficiently, that gas breaks free at the weakest spots in the dry ice layer, which are either at the dune crest or at its base, or sometimes on its face where cracks form. When it does so the CO2 gas carries with it material from below, which appears dark relative to the bright dry ice on the surface. As the summer season progresses and more dry ice sublimates away, the dark smudges disappear as they slowly blend in with the now-exposed original sand surface.

The first two pictures to the right were posted in that June 6, 2019 story, showing the initial evidence of sublimation on a set of dunes that the scientists have dubbed Buzzell. Below these, I have now added the newest image of the Buzzell dunes, taken on June 4, 2019 and just released in the August MRO image dump.

When this third image was taken, spring was only about two months old. Yet, this sublimation process is clearly accelerating. You can see many more dark patches at the crests and bases of many dunes, especially in the upper left of the image. According to Dr. Candice Hansen of the Planetary Science Institute in Tucson, Arizona, who is requesting these monitoring images, by sometime in October “you’ll see how the entire spring progresses from dunes completely covered with dry ice to the summer when they are just bare sand. Then you could comment on the whole spring series.”

I fully intend to do this. No harm however in providing an interim report or two. Stay tuned to Behind the Black for future on-going and up-to-date reports on the shrinking north pole dry icecap of Mars!

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Crater on the Basement of Mars

12:05 pm

Crater in the bottom of Hellas Basin
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Cool image time! In the July release of images from the high resolution camera of Mars Reconnaissance Orbiter (MRO) was the image to the right, cropped to post here, showing what I suspect is a relatively young crater located in the lowest part of Hellas Basin, what I call the bottom of Mars.

Though this crater is not located at the lowest point in Hellas, it is not far off from there. What makes it important to geologists are two facts. First, there are not a lot of craters in Hellas, which helps indicate it is a relatively young feature. Second, and more important, the impact has made accessible material from below the surface, indicated by the different colors in this image. From this information they can better constrain their theories about the Basin’s formation and where it fits in Mars’s overall geological history.

Make sure you take a look at the full photograph by clicking of the image, and compare it with the earlier Hellas Basin images I posted here. The surface of Hellas appears to have a lot of flow features, as if it was laid down by volcanic activity, or by the motion of water that covered it. In either case that would explain the overall lack of craters.

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A bullseye on Mars

1:57 pm

Layered crater at equator
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Cool image time! In researching my piece last week on the glaciers of Mars I had wanted to include a picture of a typical concentric glacier-filled crater, the most widespread glacial feature on the Martian surface, found in a band at latitudes between 30 and 60 degrees. (You can see the example I found at the link above, near the end of the article.)

To find that picture I searched the Mars Reconnaissance Orbiter (MRO) archive. Among the images I found was a captioned image taken very early in MRO’s mission showing a crater with concentric rings very similar to the concentric glacial-filled craters. The image at the right is that crater, the image reduced and cropped to post here. As described in that caption,
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