Tag: geology

Perseverance’s future increasingly rocky road

October 21, 2024 11:51 am Robert Zimmerman

Click for original image.

Though nothing in any image so far from the Mars rover Perseverance matches the rocky terrain that the rover Curiosity has been traversing for the past two years as it climbs Mount Sharp in Gale Crater, as Perseverance has been climbing up the rim of Jezero Crater in the past few weeks it is beginning to get a hint of a future rougher road.

The photo to the right, cropped, reduced, and sharpened to post here and taken on October 20, 2024 by one of the rover’s high resolution cameras, is a good example. It looks uphill in the direction that the rover will travel. Note how as you go higher the ground appears to be more strewn with rocks and boulders. Another image, taken the same day by the rover’s high resolution camera, shows a close-up of an even more boulder-covered landscape.
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Young lava on the Moon?

October 21, 2024 9:08 am Robert Zimmerman

Click for original image.

Cool image time! The photo to the right, cropped and reduced to post here, was taken on November 27, 2023 by Lunar Reconnaissance Orbiter (LRO) and was today featured by the science team. From their caption:

One of the early findings from the LRO mission was the discovery of volcanic features known as Irregular Mare Patches (IMPs) scattered across the nearside. These landforms are generally considered volcanic. However, their ages are hotly debated. They may be as young as 50 million years or as old as 3.5 billion years. The Aristarchus IMP (25.045°N, 313.233°E) is one of the smallest and most enigmatic IMP. The fact that this IMP is found within the Aristarchus crater ejecta suggests it formed after the crater, which is dated at 200 million years.

Alternatively, this IMP may have formed as part of ejecta emplacement from the Aristarchus crater forming impact. However, no other crater ejecta on the Moon exhibits a similar landform.

Astronomers for decades before and since Sputnick have reported what appears to be some activity in the Aristachus region, though none of those reports have ever been confirmed. In LRO’s long mission orbiting the Moon it has not yet detected any obvious changes there, suggesting that there is little or no present activity. These patches however appear to indicate activity in the relatively recent past.

The patches however also indicate activity that seems alien. Why would the lava form in this manner, as rough patch of knobs, sometimes aligned, sometimes not?

A different kind of chaos on Mars

October 18, 2024 2:25 pm Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on June 23, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I had originally chosen to feature a different picture of this spot, taken on August 1, 2024 in order to create a stereo pair, but this week the camera team featured this first photo, providing a caption.

This disrupted surface is characterized by a collection of rounded to flat-topped mounds of various sizes connected by narrow flat floors, typical of the aptly named “chaotic terrain” on Mars.

What could have caused this flat surface to break into pieces? You might imagine that a flat surface could be broken up if it was inflated or collapsed. One hypothesis is that large amounts of water were released from deep below the ground to cause the surface break up.

Normally on Mars, especially in the mid-latitudes, chaotic terrain is associated with glacial activity, suggesting that glaciers over time erode valleys along random criss-crossing fault lines to create the mesas and canyons. This patch of chaotic terrain however suggests a different formation process.
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Spring etch-a-sketch near the Martian south pole

October 16, 2024 1:06 pm Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on May 28, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled merely as a “terrain sample,” it was likely snapped not as part of any specific research project but to fill a gap in the camera’s schedule so as to maintain its proper temperature.

The camera team tries to find interesting geology when they do this, and are frequently successful. In this case the image shows some truly alien Martian terrain at 77 degrees south latitude, about 475 miles from the south pole.

What are we looking at? I promise you it isn’t the iron filings found inside an Etch-A-Sketch drawing toy. My guess is that the base layer is the light areas, a mixture of ice and debris impregnated with dust and eroded into the unique Martian geological feature dubbed brain terrain. As for the dark lines and splotches, their explanation might lie in the time of year, the spring.
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First test images sent back by Hera asteroid probe

October 15, 2024 9:19 am Robert Zimmerman

Click for original image.

During its initial in-space commissioning to make sure everything is working properly after an October 7, 2024 launch, engineers have successfully taken the first test images by Hera asteroid probe, proving those instruments are operating as intended.

The picture to the right, cropped, reduced, and sharpened to post here, was taken by the spacecraft’s mid-infrared camera, and shows both the Earth (lower left) and the Moon (upper right) as seen from a little less than a million miles away. Once Hera reaches the binary asteroid system of Didymos and Dimorphos, this instrument will be used to measure the changes of temperature on the asteroids’ surface.

Images of Earth taken by two other instruments proved those instruments were functioning properly as well.

Hera is a European Space Agency (ESA) follow-up asteroid mission to see up close what changes were caused to Dimorphos by the impact of NASA’s Dart mission in 2022. It will rendezvous with the asteroid in late 2026 after flying past Mars and its moon Deimos in earlier that year. It will then spend about a half year flying in formation with the asteroids before a planned landing in late July 2027.

The pimpled floor of Isidis Basin on Mars

October 10, 2024 1:30 pm Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on May 21, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled merely as a “terrain sample,” it was likely taken not as part of any specific research project but chosen by the camera team to fill a gap in the camera’s schedule in order to maintain its proper temperature.

When they do this they try to pick a target that is somewhat interesting, though it is not always possible. In this case it appears they succeeded in capturing a location filled with lots of puzzling stuff, including low 60-to-80-foot-high mesas with either flat- or hollow-tops, shallow craters that appear almost buried, and other craters that appear so deep and shadowed that it is even possible these are skylights into underground caves.

In between these features the flat landscape has a scattering of ripple dunes, all oriented in the same direction and thus implying that the prevailing winds are or were blowing from the northeast to the southwest.
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Monitoring a changing spot on Mars

October 9, 2024 1:12 pm Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 18, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Based on its label, “Dark Filamentary Streak Year-Round Monitor Site in Promethei Terra,” it was apparently taken as part of a long-term project to monitor the changes that occur at this particular spot on Mars.

This monitoring began in 2008, not long after MRO began science operations. In that first image, taken in the Martian autumn, almost the entire terrain was covered with dust devil tracks, all running more-or-less parallel to each other in a northwest-to-southeast direction.

That unusual tiger-striped landscape prompted later monitoring. However, a follow-up photo in 2010, also in autumn, showed practically no dust tracks here at all. Another image, taken in 2011 during the Martian summer, showed new dust devil tracks, but instead of being aligned as in 2008, the tracks went in all directions, with only a hint of alignment to the southeast.
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Curiosity’s upcoming travel route

October 8, 2024 12:36 pm Robert Zimmerman

Click for original image.

Click for interactive map.

Cool image time! The panorama above, cropped and annotated to post here, was taken on October 6, 2024 by the right navigation camera on the Mars rover Curiosity. It looks south, down the slopes of Mount Sharp and across Gale Crater, the distant crater rim barely visible through the dusty air twenty to thirty miles away.

The overview map to the right provide the context. The blue dot marks Curiosity’s present position. The yellow lines the approximate area covered by the panorama. The red dotted line indicates the rover’s planned route, with the white dotted line the path it has recently traveled.

As you can see, the rover has moved up onto a higher terrace surrounding the Texoli butte, and will now travel downhill a bit to skirt around its northern nose. From there, the science team plans to send the rover westward, traversing along the contour lines on the side of Mount Sharp. Along the way it will lose more elevation, but eventually, after passing several parallel north-south trending canyons, it will finally turn south into one canyon to resume its climb up the mountain.

To review the rover’s journey, Curiosity during its dozen years on Mars has traveled just over 20 miles and climbed about 2,500 feet. The peak of Mount Sharp however is still about 26 miles away and about 16,000 feet higher. Getting there will probably take at least three more decades, which is possible since the rover uses a nuclear power source similar to that used by the two Voyager interplanetary probes, now functioning in space for almost a half century.

In fact, it would not surprise me if the first human Mars colonies are established while Curiosity is still working, and that in its later years it sends its data to that colony directly (via an orbiting relay satellite), rather than beaming it back to Earth.

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Scientists: both liquid water and ice shaped Gale Crater

October 8, 2024 9:38 am Robert Zimmerman

The uncertainty of science: Using isotope data from instruments on the Mars rover Curiosity, scientists have found evidence that suggests that both liquid water as well as glacial ice helped shape the present geology in Gale Crater.

The paper proposes two formation mechanisms for carbonates found at Gale. In the first scenario, carbonates are formed through a series of wet-dry cycles within Gale crater [involving intermittent liquid water]. In the second, carbonates are formed in very salty water under cold, ice-forming (cryogenic) conditions in Gale crater [involving glacial ice].

“These formation mechanisms represent two different climate regimes that may present different habitability scenarios,” said Jennifer Stern of NASA Goddard, a co-author of the paper. “Wet-dry cycling would indicate alternation between more-habitable and less-habitable environments, while cryogenic temperatures in the mid-latitudes of Mars would indicate a less-habitable environment where most water is locked up in ice and not available for chemistry or biology, and what is there is extremely salty and unpleasant for life.”

…The heavy isotope values in the Martian carbonates are significantly higher than what’s seen on Earth for carbonate minerals and are the heaviest carbon and oxygen isotope values recorded for any Mars materials. In fact, according to the team, both the wet-dry and the cold-salty climates are required to form carbonates that are so enriched in heavy carbon and oxygen.

What I glean from this report is that the evidence that ice played the dominant role continues to build, but since it counters the liquid water theories that scientists have favored for decades they are reluctant to shift entirely to it. It also suggests the geological processes on Mars were far more complex than proposed (no surprise!), and that some mixture of both processes was likely.

This paper is of course merely a newly proposed hypothesis, and therefore its conclusions should be considered only with great skepticism.

Frozen Martian eddies at the confluence of two glacier rivers

October 4, 2024 1:46 pm Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on July 3, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels the photo as capturing a “contact near Reull Vallis,” a 1,000-mile-long Martian canyon that flows down the eastern slopes of Hellas Basin, the death valley of Mars.

What I see isn’t a geological contact but a complex jumble of odd-shaped depressions and mesas, surrounded by an eroded surface that seems squashed and deformed by some process. If this is all we had to go on, I would simply label this as another “What the heck?” image on Mars and move on. However, the larger context of the overview map helps explain it all, at least as best as we can explain using orbital data.
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Water on the Moon? New data analysis from two different lunar orbiters say yes

October 3, 2024 10:04 am Robert Zimmerman

Two papers in the past month using data from two different lunar orbiters have claimed the presence of water on Moon, based on the detection of evidence of hydrogen on the surface.

First, on September 16, 2024 scientists published a paper [pdf] that analyzed data collected in 2009 by India’s Chandrayaan-1 lunar orbiter, and concluded, as stated enthusiastically in the press release:

From the second paper, a map of permanently shadowed
regions at the Moon’s south pole. Click for original.

“Future astronauts may be able to find water even near the equator by exploiting these water-rich areas. Previously, it was thought that only the polar region, and in particular, the deeply shadowed craters at the poles were where water could be found in abundance,” said Roger Clark, Senior Scientist at the Planetary Science Institute and lead author of “The Global Distribution of Water and Hydroxyl on the Moon as Seen by the Moon Mineralogy Mapper (M3)” that appears in the Planetary Science Journal. “Knowing where water is located not only helps to understand lunar geologic history, but also where astronauts may find water in the future.”

Then today NASA announced the publication of a new paper [pdf] that looked at the data collected over the last decade by Lunar Reconnaissance Orbiter (LRO), and have concluded that “hydrogen-bearing volatiles are observed to be concentrated, likely in the form of water ice, within most of the Moon’s permanently shadowed regions (PSRs), poleward of 77°.” The press release, which included the map to the right of permanently shadowed areas at the Moon’s south pole, was more enthusiastic:
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The strange terrain of the Martian southern ice cap

October 2, 2024 12:13 pm Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, rotated, cropped, and sharpened to post here, was taken on July 29, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a section at the Martian south pole at the very high latitude of 87 degrees south, only about 100 miles from the pole itself.

The label for this picture is “possible water ice and mesas,” suggesting we are looking at an ice cap of water that is partly sublimated away.

In truth, things are much more complicated. It was summer when this photo was taken. Note the drainage in the lower right and the dark spidery lines there. In the winter on Mars atmospheric carbon dioxide falls as snow and coats the poles to about 60 degrees latitude with a thin mantle of dry ice. In the spring this mantle sublimates away, but does so in an counter-intuitive manner. The sublimation first occurs at the mantle’s base, and the trapped gas flows up until it finds a weak spot in the mantle and cracks through, spewing out and deposting dark splotches of dust.

At the south pole this upward flow always follows the same paths, producing the dark spidery patterns we see here. In the case of the drainage in the lower right, this is a drainage of gas eastward until it pops out at the slope, causing that depression to become darkly stained.

This is only part of the story of this complex geology, however.
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Scientists detect jets of carbon dioxide and carbon monoxide from asteroid

October 2, 2024 9:45 am Robert Zimmerman

Click for original graphic.

Using the spectroscopy from the Webb Space Telescope, scientists have now detected jets of carbon dioxide and carbon monoxide spewing from the very active asteroid 29P/Schwassmann-Wachmann-1 (29P).

Based on the data gathered by Webb, the team created a 3D model of the jets to understand their orientation and origin. They found through their modeling efforts that the jets were emitted from different regions on the centaur’s nucleus, even though the nucleus itself cannot be resolved by Webb. The jets’ angles suggest the possibility that the nucleus may be an aggregate of distinct objects with different compositions; however, other scenarios can’t yet be excluded.

The graphic to the right illustrates the modeling of these jets. That the center of this two-lobed asteroid could have been created from distinct objects suggests a very complex formation process, since those objects would have had to have formed themselves in different locations in the solar system and then somehow come together.

Perseverance looks uphill

September 30, 2024 9:51 am Robert Zimmerman

Click for full resolution. The original images can be found here and here.

Cool image time! The panorama above was created by me from two pictures taken today by the left navigation camera on the Mars rover Perseverance (found here and here). The haziness in the air is the left over from a local dust storm in Jezero Crater during the past month.

On the overview map below, the blue dot marks Perseverance’s present position, with the red dotted line indicating the approximate planned route of the rover uphill. The yellow lines are my guess as to the area covered by the panorama above. That guess could be wrong, as not all the features in the picture match the overview map. The view could be much closer, with the hill and ridgeline nothing more than the small outcrops close to the rover.

Nonetheless, these navigation pictures show us the kind of terrain the rover will be climbing as it works its way up the rim of Jezero Crater. The ground is relative smooth, though steep. My guess is that this is about a 25% grade, which on Earth would be a problem but on Mars it is a grade that NASA’s other rover, Curiosity, has routinely traversed. Perseverance has not yet traveled this kind of steepness, but there is no reason to expect it to have any difficulties doing so.

Click for interactive map.

Curiosity spots a corroded weathered rock

September 30, 2024 9:15 am Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 29, 2024 by the close-up camera mounted at the end of the robot arm of the rover Curiosity on Mars.

This is a small rock, less than three inches across. It is embedded in the sand and soil of Mars, its surface clearly weathered and smoothed by some process. The holes and gaps in the rock could have occurred prior to that smoothing, getting exposed by it. Or possibly the holes developed during the smoothing, with sections breaking off because the material was like sandstone, easily friable.

What caused the smoothing? The data from Curiosity as it climbs Mount Sharp suggests some water process, either flowing water or glacial ice. The scientists at present tend to prefer the liquid explanation, but that requires the Martian atmosphere to have once been much thicker and warmer, conditions that no model has yet demonstrated convincingly was ever possible.

The rock is also likely another example of sulfur, part of the sulfate-bearing unit of geology that Curiosity is presently traversing.

Crazy swirling Martian landscape

September 27, 2024 1:48 pm Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, cropped, reduced, sharpened, and annotated to post here, was taken on July 1, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labels this “Contacts between Likely Sulfates and Chaos Blocks.” That contact I have indicated with the dotted line. To the west the lighter terrain is likely the sulfate-bearing unit, similar to the sulfate-bearing unit that Curiosity has been traversing on Mount Sharp for the past year or so.

To the east are the chaos blocks, but I think that description is wholly inadequate. In truth, I haven’t the faintest idea how this terrain got to be the way it is. It is evident that a lot of dust and sand has gotten trapped in the hollows, leaving behind ripple dunes in some places, but why the higher ridges swirl and curve about as they do is utterly baffling.
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Monitoring gullies on Mars for changes

September 25, 2024 12:25 pm Robert Zimmerman

Overview map

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and enhanced to post here, was taken on June 29, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The scientists label the picture simply as “gully monitoring,” with an apparent goal of looking to see if this gully has changed since MRO took the first high resolution image two years previously. In the interim this terrain went from Martian spring, through summer and winter, and has now returned to spring.

As far as I can tell, no changes are visible, but then I am not using the highest resolution data available. Small changes might be detectable in the highest resolution using good detection software. Overall, the gully drops about 3,000 feet.

The white dot in the overview map above marks the location, on the southwest interior rim of an unnamed 30-mile wide crater. This region in the Martian cratered highlands was featured in a four part cool image series I did back 2023 (here, here, here, and here), with this as my conclusion:

Overall, our short survey of the southern cratered highlands suggests that the glacial material and ice found in the southern mid-latitudes affects the Martian surface differently than in the northern lowland plains. In the north the craters and the surrounding terrain often appear blobby, as if the ice is close to the surface and also a dominant component of the ground. Impacts therefore cause significant soft melt features, with craters often heavily distorted. Similarly, there is evidence of the existence of past mud volcanoes that once spewed water and mud from below ground.

In the south however the surface is at a higher elevation, and it appears the ice layer is deeper underground. Thus, it appears the ground is more firm, and the only obvious evidence of an underground layer of ice is revealed when sublimation and the subsequent erosion produce these large pits inside craters.

In the case of this crater, a small impact on its interior southwest slope apparently caused that underground layer of ice to melt temporarily and flow downhill, leaving behind the gully and flow features we see today. Based on the two MRO pictures taken a full Martian year apart, it appears the feature is generally stable and thus likely old, left over from that impact. If things are changing seasonally they are doing so in small amounts and slowly.

A puzzling striped rock on Mars

September 25, 2024 9:32 am Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 13, 2024 by one of the high resolution cameras on the Mars rover Perseverance. The rock’s striped nature makes it unique, unlike any feature spotted by any rover previously. From an update today:

The science team thinks that this rock has a texture unlike any seen in Jezero Crater before, and perhaps all of Mars. Our knowledge of its chemical composition is limited, but early interpretations are that igneous and/or metamorphic processes could have created its stripes. Since Freya Castle [the name the science team gave the rock] is a loose stone that is clearly different from the underlying bedrock, it has likely arrived here from someplace else, perhaps having rolled downhill from a source higher up. This possibility has us excited, and we hope that as we continue to drive uphill, Perseverance will encounter an outcrop of this new rock type so that more detailed measurements can be acquired.

Without doubt the rock’s rounded surface suggests it was ground smooth by either water or ice. That surface certainly resembles glacial cobble seen across the northeast of the U.S. where ice glaciers once covered the entire landscape. The rock also resembles river cobble, smoothed by flowing water.

The stripes however suggest that prior to its being smoothed, this rock underwent a much more complex geological process, whereby two different materials were intermixed and squeezed together.

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Layered mesas in Martian chaos

September 24, 2024 12:27 pm Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on May 19, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a 2,500 to 3,000-foot-high mesa with what the scientists call “bedrock layers”, most obvious as the lower terraces on the mesa’s western slopes.

What makes this mesa especially interesting is its overall shape. It appears as if something has taken a bite out of it, resulting in that bowl-like hollow on the mesa’s southern half.

Was this caused by an impact? Or has some other long term Martian processes caused it?

This mesa is just one of many mesas in a region of chaos terrain dubbed Hydraotes Chaos. Such chaos terrain is thought to form when erosion processes, possibly glacial in nature, that carve out canyons along faultlines, leaving behind mesas with randomly oriented canyons cutting in many directions.
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More deterioration to Curiosity’s worst wheel

September 23, 2024 12:13 pm Robert Zimmerman

Comparison of changing damage from Feb to Sept 2024
For original images go here, here, and here.

The science team for the Curiosity Mars rover on September 22, 2024 did another survey of its damaged wheels using the close-up camera on the end of the rover’s arm, and though most of the pictures appear to show the situation remains stable, the one wheel that has consistently shown the worst damage now shows some additional deterioration since February 2024.

To the right are comparison pictures, with the February 2024 picture on top and two new September 22, 2024 images showing the same damaged area, though from a different angle, on the bottom. (The technical captions for the bottom images can be found here and here.) I have labeled the treads, dubbed growsers, to make it easier to understand how the pictures all line up.

Previous images have looked down at the large damaged area from growsers 1 to 4, and since it was first spotted in 2022 showed it to be growing, but very slowly. The new pictures show that same damaged area from the side, which reveals that the zig-zag divider between growser #3 and growser #4 has now collapsed, so that this whole damaged area is now a major depression, as indicated by the two arrows.

Overall, the rover’s wheels appear to surviving the rough terrain of the foothills of Mount Sharp, though it is clear that care must continue to be taken to extend their life for as long as possible. That the rover has six wheels gives it a lot of redundancy, so that even if this one wheel eventually fails the rover will likely be able to continue to rove, but with some limitations. This wheel is the left middle wheel, which is helpful, as it is less necessary than the four corner wheels. [Update: According to a rover update today, this wheel is the right middle wheel, which contradicts an earlier report which described this as the left middle wheel. I note this contradiction for accuracy.]

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Land of cracks

September 20, 2024 1:26 pm Robert Zimmerman

Cool image time! The picture to the right, cropped to post here, was taken on June 28, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled a “terrain sample,” it was likely taken not as part of any specific research project but to fill a gap in the camera’s schedule in order to maintain its proper temperature. When the camera team needs to do this, they try to pick something interesting, but don’t always have that option.

In this case, the landscape available included the channel shown to the right. About a half mile wide and only about fifty feet deep, the floor of this canyon appears to have a lot of trapped dust, forming ripple dunes, along with a lot of knobby protrusions, likely small mesas. The canyon walls appear layered, with the erosion processes producing different features on opposite sides. On the southeast the layers appear to produce distinct terraces, while on the northwest the cliff is very steep at the top and then forms a long gently descending slope that appears formed of alluvial fill (from that cliff) and formed from erosion and landslides.
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Some new “What the heck?” geology on Mars

September 17, 2024 1:12 pm Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken on April 21, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

My first reaction on seeing this picture was to scratch my head? What am I looking at? Are those fluted dark features going downhill to the south, or uphill to the north? What are they? Are they slope streaks? Avalanches? How do they relate to the flat-topped ground in the middle of the picture?

I have made it easier for my readers to interpret the picture by adding the “low” and “high” markers. We are looking at two parallel thin mesas about 1,400 feet high, with the saddle between them only dropping about 350 feet.

But what about the dark fluted features? To understand what these are requires more information.
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Perservance looks back from on high

September 13, 2024 10:25 am Robert Zimmerman

Click for original image.

Cool image time! The picture above, cropped to post here, was taken on September 9, 2024 by the left navigation camera on the Mars rover Perseverance, looking east and back along the route from which the rover had come.

The view is somewhat more spectacular than most Perseverance images because the rover took it during its on-going climb up unto the rim of Jezero Crater, as shown by the overview map below. The blue dot marks Perseverance’s present position, while the yellow lines indicate the area covered by the picture above, taken several days earlier.

The haze in the picture also suggests that the local dust storm first noted in late August might be clearing somewhat. This isn’t certain, however, as the previous picture was using the rover’s high resolution camera to look at distant hills (thus more obscured), while the picture above was taken by the left navigation camera looking more widely and at nearer objects.

Click for interactive map.

New gravity map of Mars released

September 13, 2024 9:09 am Robert Zimmerman

Click for original image.
Using both seismological data compiled over four years by the InSight Mars lander as well tiny changes in the orbits of Martian satellites, scientists have now created a global gravity map of the red planet, indicating the regions below the surface that are either low or high density.

That map is above, annotated by me to indicate some of Mars’ major surface features.

The density map shows that the northern polar features are approximately 300-400 kg/m3 denser than their surroundings. However, the study also revealed new insights into the structures underlying the huge volcanic region of Tharsis Rise, which includes the colossal volcano, Olympus Mons.

Although volcanoes are very dense, the Tharsis area is much higher than the average surface of Mars, and is ringed by a region of comparatively weak gravity. This gravity anomaly is hard to explain by looking at differences in the martian crust and upper mantle alone. The study by Dr Root and his team suggests that a light mass around 1750 kilometres across and at a depth of 1100 kilometres is giving the entire Tharsis region a boost upwards. This could be explained by huge plume of lava, deep within the martian interior, travelling up towards the surface.

I once again note that the largest impact basin on Mars, Hellas Basin, sits almost exactly on the planet’s far side from Tharsis, and appears to have a light density. This contrast once again makes me wonder if the origin of that impact and the Tharsis Bulge are linked.

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A fluted mesa on Mars

September 12, 2024 1:27 pm Robert Zimmerman

Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on July 9, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labels a “silica-rich mound”, as indicated by the bright streaks on all the high ridge points.

The flat-topped mesa on the right drops about 200 feet to the valley floor. The rims of that depression to the west rise about 50+ feet higher, while mesa nose in the upper left rising another 50+ feet more.

Was the depression caused by an impact? If so, the landscape has changed radically since that impact occurred, with most of the surrounding terrain eroded away. The two flat-topped mesas hint at the ancient surface when that impact occurred.

A wider view however raises questions about this impact theory.
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Scientists re-create on Earth the sublimation of Mars’s winter mantle of dry ice

September 12, 2024 11:32 am Robert Zimmerman

Click for original image.

Scientists have successfully re-created on Earth the process on Mars that creates the unique “spider” formations seen in the the Martian south pole region, produced when the winter mantle of dry ice begins to sublimate away into a gas.

The study confirms several formation processes described by what’s called the Kieffer model: Sunlight heats the soil when it shines through transparent slabs of carbon dioxide ice that built up on the Martian surface each winter. Being darker than the ice above it, the soil absorbs the heat and causes the ice closest to it to turn directly into carbon dioxide gas — without turning to liquid first — in a process called sublimation (the same process that sends clouds of “smoke” billowing up from dry ice). As the gas builds in pressure, the Martian ice cracks, allowing the gas to escape. As it seeps upward, the gas takes with it a stream of dark dust and sand from the soil that lands on the surface of the ice.

At the south pole, the ground below the mantle is stable enough that each winter the trapped CO2 gas follows the same path to the same points where the dry ice cracks, slowly creating “tributaries” that combine to form the spider formations.

The picture to the right, cropped, reduced, and sharpened to post here, comes from figure 9 of the paper [pdf]. It shows the lab-created spiders formed by this simulated process, thereby confirming this hypothesis about how the spiders form.

A map of Io’s hot spots based on Juno data

September 11, 2024 1:12 pm Robert Zimmerman

Click for original image.

The uncertainty of science: Using the JIRAM infrared camera on the Jupiter orbiter Juno, scientists have now created a global map of volcanic activity, showing where it appears the hottest and greatest activity is located.

That data is illustrated by the graphic to the right, taken from figure 1 of the paper. The top row shows the coverage of the planet, with Io’s southern hemisphere getting the fewest observations. The bottom row shows the observed regions with the greatest heat. This quote from the abstract is most revealing:

Using JIRAM, we have mapped where volcanoes are producing the most power and compared that to where we expect higher heat flow from the interior models. Our map doesn’t agree with any of these models very well. JIRAM observed more volcanic activity at the poles than we expected to see based on previous observations. However, since the south pole was only observed twice, it’s possible that these observations don’t represent the average volcanic activity of the south pole. Very bright volcanoes that may have been continuously active for decades were also imaged during these Juno fly-bys, some of which are nearer the poles than the equator.

The conflict between the data and the theories could very well be explained simply by the short term nature of these observations. The models could very well be right, over centuries. For example, the new volcano discovered by Juno is near the equator, suggesting with time those models will turn out to be correct.

Or not. A lot more observations will have to be made of Io before any model of its volcanic activity can be considered trustworthy.

Juno discovers new volcano on Io

September 11, 2024 10:24 am Robert Zimmerman

Click for original image.

By comparing images taken twenty-seven years apart by the the Jupiter orbiters Galileo and Juno, scientists have discovered that during that time a new volcano appeared on the volcano-strewn Jupiter moon Io.

The two pictures to the right show the surface change on Io during those 27 years.

Analysis of the first close-up images of Io in over 25 years, captured by the JunoCam instrument on NASA’s Juno mission, reveal the emergence of a fresh volcano with multiple lava flows and volcanic deposits covering an area about 180 kilometres by 180 kilometres. The findings have been presented at the Europlanet Science Congress (EPSC) in Berlin this week.

The new volcano is located just south of Io’s equator. Although Io is covered with active volcanoes, images taken during NASA’s Galileo mission in 1997 did not see a volcano is in this particular region – just a featureless surface.

If anything, it has been somewhat surprising how little change the new Juno images have found on Io’s surface, considering its intensely active volcanic geology, with volcano plumes from eruptions captured in images repeatedly. Some volcanoes have shown change, but new features such as this new volcano have not previously been identified.

At the same time, the amount of high resolution imagery of the planet’s surface has been somewhat limited. Galileo sent back far fewer pictures than planned because its main antenna never deployed, and Juno had only a handful of close fly-bys. It will take a mission dedicated to studying Io to better map its violent surface.

The reasons why Mars two polar caps are so different

September 10, 2024 1:06 pm Robert Zimmerman

The Martian north pole.

The Martian south pole.

Elevation scale bar
What the colors mean in terms of elevation

A new paper, in review for the past year, has now been published describing the differences between the north and south poles of Mars, the most fundamental of which involve the planet’s orbit and the different elevations of the two poles, with the south pole three to six miles higher in altitude (as indicated by the colors on the maps to the right).

The cumulative data has allowed the researchers to explain why — when the thin winter cap of dry ice sublimates away in the spring — the process at the south pole results in spiderlike features that get enhanced from year to year, but in the north pole that sublimation process produces no such permanent features.

In both cases, the spring sunlight passes through the clear winter mantle of dry ice to heat its base. The sublimated trapped CO2 gas builds up, until the pressure causes the mantle to crack at weak spots. In the south that trapped gas flows uphill each spring along the same paths, carving the riverlike tributaries dubbed unofficially as “spiders” and officially as “araneiform terrain.”

Geophysicist Hugh Kieffer described that process in 2006. A few years later, [Candice] Hansen [the new paper’s lead author] followed up with her own model for the north polar cap, which also displays fans in the spring.

She found that the same phenomena occur in the north, but rather than relatively flat terrain, these processes play out across sand dunes. “When the Sun comes up and begins to sublimate the bottom of the ice layer, there are three weak spots – one at the crest of the dune, one at the bottom of the dune where it meets the surface and then the ice itself can crack along the slope,” Hansen said. “No araneiform terrain has been detected in the north because although shallow furrows develop, the wind smooths the sand on the dunes.”

There is also a lot more dust in the north, including a giant sea of dunes that circles the polar cap. In addition, the northern winter is shorter due to the planet’s orbit, and takes place during the annual dust storm season, causing there to be more dust concentrated within the northern ice. All of these factors make the the dunes and general surface in the north is more easily smoothed by the wind.