Tag: geology

The lacy rocks of Mars

9:36 am

Lacy rocks on Mars
Click for full image.

Cool image time! The image to the right, cropped and reduced to post here, was taken on July 16, 2021 by the Mars rover Curiosity, using its high resolution mast camera.

There isn’t much to say. These are alien rocks, created in a place with a gravity only about a third that of Earth’s in a climate that is very different. Their delicate nature suggests we are looking at something that was once more substantial and has since been undergoing erosion.

Nor has it been that unusual to find rocks so dainty on Mars. In fact, the more Curiosity has climbed, the more such things have been visible. And similar things were seen by the rovers Spirit and Opportunity.

How such rocks formed initially in the far past, under what climate conditions, remains the number one mystery on Mars. What is now causing it to flake away into such a finespun gossamer of complexity is as much a mystery, tied more to the climate and geology of Mars today.

This rock sits on the bottom flank of Mt Sharp in Gale Crater, at the highest elevation Curiosity has yet climbed. At this point the rover has just entered a new geological unit, what scientists have dubbed the sulfate unit. The evidence gathered from a distance (that so far appears confirmed by recent observations) suggest that this unit was formed under a fluctuating environment that laid down many layers of sediment as conditions ebbed and flowed.

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First attempts to map the layered geology of Mars

1:47 pm

layers in Jiji Crater on Mars
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Today’s cool image illustrates well the central task of much of today’s geological research on Mars, using the orbital images to try to map out the visible geological layers seen, and figure out if those layers mark over wide regions specific geological epochs, as they do on Earth.

The photo to the right, cropped and reduced to post here, was taken on May 4, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and featured on July 12th as a captioned image entitled “Layers Blanket a Crater Floor.” From the caption:

This image shows a layered rock formation within Jiji Crater that has eroded into buttes and stair-like layers.

This formation extends west and east. Similar layered rocks are within several craters in Arabia Terra and Meridiani Planum, including [nearby] Sera and Banes craters. The similarities suggest that the same process was forming deposits over a large geographic area long ago. Our image also indicates that much of the formation has eroded away relative to what has remained.

As you can see in the photo, the layers form a neat staircase of terraces descending from the south crater rim to the crater floor. They suggest that once the crater was filled with this material, which over time eroded away.

An image of similar layered buttes and mesas in Sera crater, only about 20 miles away, was featured here on Behind the Black in December 2020 The overview map below shows the relationship between Jiji, Sera, and Banes craters.
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Craters on Ganymede’s striped surface

11:27 am

Craters on Ganymede
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Cool image time! The photo to the right, cropped to post here, is a color enhanced section taken from of one of the images taken by Juno when it did a close fly-by of the Jupiter moon Ganymede back on June 7, 2021.

The enhancement was done by citizen scientist Navaneeth Krishnan, using a wider Juno image of Ganymeded enhanced by citizen scientist Kevin Gill. That wider image is below, and marks the area covered by this first image with a white box.

In this one picture we can see many of the geological mysteries that have puzzled scientists since the Galileo orbiter first took close-up images back in the 1990s. We can see patches of grooved terrain with the grooves in the different patches often oriented differently. We can also see bright and dark patches that while they overlay the grooved terrain they bear no correspondence to those grooved patches. And on top of it all are these small craters, impacts that obviously occurred after the formation of the grooves.
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Clashing layers in Mars’ largest canyon

1:20 pm

Clashing layers on a mountain slope on Mars
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on May 27, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows the clash of different layers on the western slope of a mountain within Mars’ largest canyon, Valles Marineris.

The scientist have labeled this a “possible angular unconformity.” In geology an unconformity generally refers to a gap in a series of layers, a period when instead of the layers being deposited they are being eroded away, leaving no record for that time period. An angular unconformity adds tilting to the older layers, which after erosion are then covered by new layers that are oriented somewhat differently.

Based on these definitions, what the scientists suspect is that the brighter layers to the left and lower down the mountain are older. After a period of erosion new layers were deposited on top at a different angle, forming the stripe of layers going from center left up to center right.

The swirly nature of the material on the top of the ridge suggests to me that these layers might be volcanic in nature, but that’s a pure uneducated guess. What some scientists do believe (but have not yet conclusively proven) is that the lower older layers are sediments laid down by an ancient lake that once filled the canyon here.

The overview map below provides a wider view and some context.
» Read more

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Ingenuity’s view of Jezero Crater during its 9th flight

11:57 am

Ingenuity looks across Jezero Crater
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Overview map
Click for interactive map.

Cool image time! The photo above, cropped, enhanced, and reduced to post here, was taken on July 5, 2021, about thirty seconds after Ingenuity had taken off on its 9th flight on Mars. I have increased the contrast slightly to bring out the features. This is a raw image, so I do not think the colors are accurate, and I also do not know why the middle of the image is brighter than the edges.

The red lines on the map to the right indicates the general area this image captures. Essentially, once the helicopter reached its flying altitude after liftoff the engineers had it tilt so that it could see the route it was about to take to the southwest. As they noted in their description of this flight,

We began by dipping into what looks like a heavily eroded crater, then continued to descend over sloped and undulating terrain before climbing again to emerge on a flat plain to the southwest.

I think that crater is visible on the left edge of this picture.

So far 180 raw images from Ingenuity have arrived at JPL. There might be a few more, but I think this is the bulk from the flight. Of these, all but nine are black and white and point straight down. The nine color images seem tilted up towards the horizon to various degrees, though the image above is the only one that captures the horizon itself and the distance mountains of Jezero Crater’s rim.

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Curiosity looks across at the alien landscape of Gale Crater

2:25 pm

Curiosity's view across Gale Crater
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Most of the images from Curiosity that I have posted recently have been of the spectacular mountain scenery looking south at Mount Sharp itself. Today’s cool image, taken on July 6, 2021 by the rover’s right navigation camera and cropped to post here, instead looks north, out across the floor of Gale Crater to its distant rim about twenty miles away.

The rover is likely not to move for a week or so, as it has just completed drilling its first drillhole since it moved up into the next geological layer, dubbed the sulfate unit. Because of this they have been using the rover’s cameras to take a lot of pictures of the surrounding terrain, including several high resolution mosaics.

The two overview maps below show what the cool image above is looking at.
» Read more

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Update on Ingenuity’s 9th flight

9:55 am

Ingenuity's 9th flight
Click for interactive map

Ingenuity’s engineering team late yesterday posted an update on the helicopter’s successful 9th flight on July 5th, describing in detail the changes they made to their software that made the challenging flight possible.

The changes were required because the helicopter flew for the first time over much rougher terrain then initially planned, as shown by the map to the right.

Flight 9 was not like the flights that came before it. It broke our records for flight duration and cruise speed, and it nearly quadrupled the distance flown between two airfields. But what really set the flight apart was the terrain that Ingenuity had to negotiate during its 2 minutes and 46 seconds in the air – an area called “Séítah” that would be difficult to traverse with a ground vehicle like the Perseverance rover. This flight was also explicitly designed to have science value by providing the first close view of major science targets that the rover will not reach for quite some time.

In other words, Ingenuity flew for the first time over terrain that Perseverance cannot drive to, recording images from above of surface features beyond the rover’s range.

We began by dipping into what looks like a heavily eroded crater, then continued to descend over sloped and undulating terrain before climbing again to emerge on a flat plain to the southwest.

The images of that rough terrain have not yet been downloaded to Earth, but will be in the next week.

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Springtime on Martian dunes near the north pole

1:42 pm

Dunes near the Martian north pole, in the spring

Cool image time! The photo to the right, rotated and cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on April 27, 2021. It shows a strange scattering of dunes on a flat plain. The red at the top of each dune probably indicates exposed dust and sand. The white fringe is likely either water frost or the leftover mantle of dry ice that is deposited in the polar regions each winter down to 60 degrees latitude, and disappears with the coming of spring, sublimating back into carbon dioxide gas.

There are a lot of puzzles here. The overview map below provides some context, but only some.
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Perseverance’s most recent view of Jezero Crater

10:30 am

Panorama by Perseverance, Sol 130, July 2, 2021
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Overview map
Click for interactive map.

Cool image time! The panorama above, reduced to post here, is made from two navigation camera images on the Mars rover Perseverance, found here and here.

The map to the right, taken from the “Where is Perseverance?” website and annotated further by me, shows with the yellow lines what I think (but am not sure) is the area seen in the panorama.

The navigation cameras on Perseverance are more wide angle than the navigation cameras on Curiosity, in order to cover a larger area. They thus produce a slight fisheye distortion, illustrated by the curve of the horizon.

The large mountain in the center right is likely the crater rim. You can also see the knobs to the left as indicated on the overview map. The rover is now about halfway to the southernmost planned spot it is expected to reach within the floor of Jezero Crater, which is about a half to three quarters of a mile further south.

The terrain seems quite desolate and barren, which of course is no surprise, because that is what it is like on all of the surface of Mars. No plant life, just rocks and dirt. While Curiosity is now in the mountains, Perseverance remains on the crater floor, so the points of interest (from the mere tourist’s perspective) are small or far away.

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Paisley terrain on Mars

1:56 pm

paisley terrain on Mars
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Cool image time! The photo to the right, cropped and reduced to post here, is actually a somewhat old image from the high resolution camera on Mars Reconnaissance Orbiter (MRO). It was taken more than a decade ago, on December 28, 2010, and featured as a captioned image one month later. I post it now because it was recently featured as MRO’s picture of the day, and thought it deserved a new look. As the caption from 2010, written by planetary scientist Alfred McEwen, noted,

Remember those paisley shirts during the summer of love in 1967? If so, this terrain may look somewhat familiar.

How did this terrain really form? One theory is that it’s a landslide deposit, perhaps associated with draining an ancient lake.

The overview map below might help make sense of this theory.
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China releases more images & videos from Zhurong

10:33 am

Zhurong panorama looking north, June 27, 2021
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Overview map
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China today released a new panorama as well as several videos taken by its Mars rover Zhurong.

The videos show the rover’s landing as well as two short videos taken from the remote camera it had dropped off shortly after deployment from its lander, the first showing the rover moving away and the second showing it turning in place.. China also released sound recorded during that deployment, as the rover rolled down the ramps. The sound was of course enhanced, but it does allow scientists to learn something about the atmosphere of Mars.

The image above is a cropped section from the panorama. The map to the right, taken on June 11th by the high resolution camera on Mars Reconnaissance Orbiter (MRO), has been annotated by me to show the area I think is seen by this section of that panorama, looking due north. (For a higher resolution version that clearly shows the rover’s tracks since leaving the lander, go here.)

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Many of Mars’ geological mysteries, all in one photo

1:06 pm

Knobs, streaks, and lava channels on Mars
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Today’s cool image is fun because it contains a plethora of Martian mysteries, all packed into a very small space. The photo to the right was taken on April 29, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I have rotated, cropped, and reduced it to post here.

The uncaptioned picture was labeled “Small Channel Winding between Knobs in Tartarus Colles.” The knobs, which can be seen on either side of the thin channel within the canyon, are actually a major Martian puzzle. Tartarus Colles has a lot of them, and planetary geologists are not really sure how they formed. One 2009 paper [pdf] suggested that the cones were formed by the violent interaction of lava and ice. This earlier paper [pdf] hypothesized that both water and lava had to be flowing over the surface at the same time, producing the steam and the energy that popped the lava cones, kind of like the small convection bubbles seen when tomato sauce simmers.

The scientific literature however is not deep, and there appears to be much uncertainty about this conclusion.

The photo however contains other major Martian puzzles.
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A sample of typical but strange Martian northern lowland plain geology

1:24 pm

Typical lowland features on Mars
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Cool image time! The photo to the right, rotated, cropped and reduced to post here, was taken on April 18, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a nice sample of the typical glacial-filled craters found often in the mid-latitudes between 30 to 60 degree latitudes, surrounded by a lot of erosion features representative of these lowland northern plains.

The biggest crater is very symptomatic of what scientists have dubbed concentric crater fill, a feature that they believe reveals that there is buried ice water glaciers here, protected by a thin layer of debris. The apron of brighter material surrounding the crater could be a splash feature created during impact and now more obvious because it has been revealed as sublimation and erosion lowered the terrain nearby.

The location is north of the Cydonia region in Acidalia Planitia, several thousand miles to the northeast of the region where Viking 1 landed in 1976 and Mars Pathfinder landed in 1997, as shown in the overview map below.
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A confused river of ice on Mars

12:39 pm

A river of ice on Mars
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on March 4, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what MRO’s science team labeled a “Landform in Source Region of Harmakhis Vallis.”

They are being very correct and careful with that label. The landform here is quite clearly reminiscent of a glacier, but because they don’t yet have confirmation of its watery nature, as good scientists they can’t call it that.

I however am a mere journalist, so I am free to speculate more wildly. Sure looks like glaciers to me, the ice flowing downhill from the left to the right and flowing around that central mound.

The overview map below gives a wider context, but also makes the behavior of the glaciers here far more puzzling.
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The Mountains of Mars

12:05 pm

The mountains of Mars
Click for full resolution. The highest mountain on the right is about 450 feet high.

Even as the rover Perseverance is beginning its first science campaign on the floor of Jezero Crater, the rover Curiosity about 3,000 miles to the east has begun its climb into the mountains of Mars that surround the central peak of Gale Crater, Mount Sharp.

The mosaic above, made from two images taken by the rover’s right navigation camera (here and here), shows what Curiosity sees ahead. Since my last update on June 4th describing Curiosity’s future travels, the rover’s science team has pushed forward directly uphill towards the entrance to the canyon Gediz Vallis, visible as the gap between the mountains to the right and left in the above mosaic.

The overview map below shows the rover’s approximate present position, with the yellow lines indicating what the above photo is looking at.
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Boxwork in the basement of Mars

12:34 pm

Polygon ridges in Hellas Basin
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, shows what resembles closely what in Earth caves are called boxwork, polygonal ridges sticking out from the bedrock and usually indicating cracks filled with harder material that resist erosion.

Taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on March 23, 2021, what makes this boxwork especially interesting is its size and location. On Earth cave boxwork generally ranges from a few inches to a few feet across. Not only do these Martian ridges range from 100 feet to a half mile in length, they are located at the lowest point in Hellas Basin, the basement of Mars. In fact, this spot is as close as you can get to Mars’ Death Valley, as shown by the overview map below.
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Zhurong finally located on Mars

11:58 am

Zhurong as seen by MRO
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Though the Chinese had earlier this week released one image taken by their Mars orbiter, Tianwen-1, showing their rover Zhurong on the surface of Mars, they did not provide any specific location information.

This lack has now been filled by a new high resolution image of Zhurong taken by Mars Reconnaissance Orbiter (MRO) on June 6, 2021. This image, cropped to match the Tianwen-1 image and annotated by me to post here, shows the parachute, entry capsule, heat shield, lander, and rover. I have added white dots to distinguish the rover from the lander, which indicate that since the Tianwen-1 orbital image the rover had moved south about 70 feet, suggesting it has been able to travel on the surface.

What this MRO image provides that the Chinese refused to reveal is the latitude and longitude of that landing site, which in turn tells us that the lander put down about 14 miles to the northwest of its targeted landing spot. The mosaic of MRO context camera images below show this landing spot in context with the surrounding terrain.
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Update on Perseverance’s future travel plans

10:47 am

Perseverance's future travels
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The science team for the rover Perseverance yesterday released a revised map of where they intend over the next few months to send the rover on the floor of Jezero Crater.

The map to the right, cropped and reduced to post here, shows that route.

The first science campaign (depicted with yellow hash marks) begins with the rover performing an arching drive southward from its landing site to Séítah-North (Séítah-N). At that point the rover will travel west a short distance to an overlook where it can view much of the Séítah unit. The “Séítah-N Overlook” could also become an area of scientific interest – with Perseverance performing a “toe dip” into the unit to collect remote-sensing measurements of geologic targets.

Once its time at the Séítah-N Overlook is complete, Perseverance will head east, then south toward a spot where the science team can study the Crater Floor Fractured Rough in greater detail. The first core sample collected by the mission will also take place at this location. After Cratered Floor Fractured Rough, the Perseverance rover team will evaluate whether additional exploration (depicted with light-yellow hash marks) farther south – and then west – is warranted.

Whether Perseverance travels beyond the Cratered Floor Fractured Rough during this first science campaign, the rover will eventually retrace its steps. As Perseverance passes the Octavia B. Butler landing site, the first science campaign will conclude. At that point, several months of travel lay ahead as Perseverance makes its way to “Three Forks,” where the second science campaign will begin.

At that point the rover will begin studying the base of the delta of material that in the far past poured through a gap in the western rim of Jezero Crater.

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Evidence of past underground water in the Martian equatorial regions?

2:30 pm

Mosaic of strange feature
Click here, here, here, and here for full images.

Today’s cool image, to the right, takes us to the equatorial regions of Mars, a region that today appears quite arid and dry based on all the orbital and rover/lander data so far gathered. The photo and its complex geology however provides us a hint that once liquid water did exist here. At least, that is the hypothesis that scientists presently favor, though making it fit this complex geology is not simple or straightforward.

The mosaic to the right is made from four context camera images taken by Mars Reconnaissance Orbiter (MRO). It shows a very complicated series of depressions — one of which vaguely resembles a crater — that appear to have been washed out by some past erosion process, though that process could not have been that simple because of the fissures and cracks that dominate the floor of the circular feature.

I contacted Chris Okubo of the U.S. Geological Survey, who had requested a high resolution image from MRO of a small part of this mosaic, as indicated by the white box, to ask him what we are looking at. His answer was appropriately noncommittal:
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Ingenuity completes 7th flight on Mars

10:21 pm

Locations of Perseverance and Ingenuity on Mars
Click for interactive map.

Ingenuity yesterday successfully completed its 7th flight on Mars, heading south and landing exactly as planned.

Ingenuity lifted off around 12:34 local mean solar time on Tuesday, which corresponds to 11:54 a.m. EDT (1554 GMT). As planned, the chopper then traveled 348 feet (106 meters) south from its previous location on the floor of Mars’ Jezero Crater, staying aloft for nearly 63 seconds, JPL officials wrote in another tweet. The solar-powered rotorcraft set down at a new airfield, the fourth one it has reached since landing on the Red Planet with NASA’s Perseverance rover on Feb. 18.

Both the rover Perseverance and Ingenuity are traveling south on the floor of Jezero Crater, with the helicopter leapfrogging ahead every few weeks. On the map the red dot indicates Perseverance location, with the green dots Ingenuity’s last three landing sites. They have not yet added to the map exactly where Ingenuity landed yesterday (#7), so I have estimated it based on the information above.

The red outline indicates the region they are planning to explore over the next few months in order to gather a very thorough understanding of the geology of the floor of Jezero Crater. They will eventually head to the northwest towards the cliffs in the upper left, which is the foot of the large delta that flowed in the past into the crater through a gap in its western rim. The route they will take to get there however remains undetermined.

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Eroding Martian lava?

12:49 pm

Eroding Martian lava?
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on April 19, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Requested by Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona, the image was entitled “Enigmatic Terrain in Elysium Planitia.” The image is labeled so because, as Dundas explained,

Flood lava is a key part of the feature, best seen at the north and south ends of the image. What’s unusual is the knobby terrain at the center. … I haven’t yet been able to do a more thorough study of these features, so plenty of puzzles remain!

The higher material in the upper right is likely flood lava. A 2016 paper [pdf] led by Dundas on similar features in Elysium Planitia that were not as knobby found their origin somewhat baffling. The evidence suggested that lava, mud, wind, and ice could all be involved in their formation, but the evidence was also not sufficient to eliminate any possibility.

In the case of today’s image, the explanation might also be any of these possibilities. For example, we might be looking at the erosion of the flood lava, exposing harder knobs of different material that had been there before and had been covered by the lava. Or maybe the knobs are simply the last bits of that layer of flood lava that has not yet eroded away.

As always, the overview map provides some context.
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Mini-volcanoes (mud or lava?) near Zhurong’s Mars landing site

2:11 pm

Mosaic of features near Zhurong's planned landing site on Mars
Click here, here, and here for full images.

Cool image time! Though we still do not know exactly where the Chinese Mars rover Zhurong landed on Mars, we have a rough idea based on the latitude and longitude numbers leaked to the Chinese press in October 2020 and were apparently confirmed by photos taken by the Tianwen-1 orbiter soon after reaching Mars. We also know Zhurong’s engineers wanted to land in the northern lowland plains dubbed Utopia Planitia, a region that is relatively flat and thus makes a safe landing spot for their first attempt to reach the surface of Mars.

The mosaic to the right, rotated and reduced to post here, is made from three context camera images taken by Mars Reconnaissance Orbiter (MRO). The white cross on the right edge is essentially Zhurong’s leaked landing spot. The red box indicates the area covered by one of only two photos that China has released that were taken by its Tianwen-1 orbiter.

The white box in the upper left shows the area covered by today’s cool image, shown below.
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NASA picks two missions to fly to Venus later this decade

2:14 pm

NASA today announced two new missions to go to Venus to study its atmosphere and surface, both scheduled to launch sometime between 2028 and 2030.

One, dubbed DAVINCI+, send a probe into Venus’s atmosphere, both to measure its gases as well as taken the first high resolution images of a unique Venusian geological called “tesserae.” On radar images tesserae regions appear to be high plateaus cross-cut with many sharp ridges.

The second, dubbed VERITAS, will be a radar-orbiter designed to map the planet’s surface at higher resolution than the earlier Pioneer and Magellan radar orbiters. It will also do this:

VERITAS also will map infrared emissions from Venus’ surface to map its rock type, which is largely unknown, and determine whether active volcanoes are releasing water vapor into the atmosphere.

That data will help tell us whether there are now active volcanoes on Venus. The data we presently have suggest it is a planet of many volcanoes, numbering in the millions. That data has also hinted at the possibility that some are active. VERITAS will attempt to find out.

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Inexplicable ridges north of China’s Mars rover

2:00 pm

Wrinkle ridges in Utopia Planitia?
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, shows some unusual geology about 450 miles north of the approximate area where China’s Zhurong rover landed in the northern lowlands of Mars. It was taken on April 14, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

These scattered ridges remind me of wrinkle ridges, formed when the surface of a place shrinks. With less surface area, the extra material needs somewhere to go, and so ridges are forced up at weak points to release the pressure.

Assuming this hand-waving explanation is true, the next question would be: What causes the shrinking? The overview map below might help provide an answer.
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A visit to a crater near the non-face on Mars

1:03 pm

Glacial erosion features inside crater
Click for full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on March 12, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It looks down at small six-mile-wide Apt crater in the northern lowland plains of Mars located at about 40 degrees north latitude. The image’s focus were the layers on the crater interior rim as well as the eroded glacial features on the crater’s floor. The color strip suggests [pdf] that the bluish material on the north-facing south interior rim and floor are likely icy, while the tan-colored material seen in the crater’s north half are likely dusty.

While the suggestion of glacial material on the crater’s interior is very typical for many craters in the mid-latitudes, what makes this crater of interest is its location, only a short few miles south of that mesa on Mars that for decades the shallow-minded insisted was a face and proof of an alien Martian civilization.
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The strange flows in Shalbatana Vallis on Mars

1:47 pm

Strange flows in Shalbaltana Vallis
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on March 31, 2021, and shows a series of very distinct arrowhead-shaped sloping ridges interspersed with hollows flowing down from the southern cliff face of Shalbatana Vallis, one of the larger long meandering drainages flowing into the northern lowlands of Chryse Planitia and north of Valles Marineris.

This location is at 5 degrees north latitude, so nothing we see in the picture is likely glacial or evidence of ice.

So what are we looking at? My guess is that the parallel ridges show us a hint of the original slope of alluvial fill. In the past canyon’s south rim or cliff either did not exist, or was much smaller. Instead the ground mostly sloped gently downhill from the plateau to the canyon floor.

Scientists believe that in the far past catastrophic floods of water flowed through Shalbatana. If a massive flood of water off that rim came down that slope of alluvial fill, it could have pushed into that fill and created the hollows, washing the fill down into the canyon floor and leaving behind the ridges in between.

The overview maps below provide the geographical context.
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Yutu-2 data suggests Moon’s far side is “bombarded more frequently” than the near side

2:55 pm

The uncertainty of science: According to a new paper, based on ground-penetrating radar data obtained by China’s Yutu-2 rover on the far side of the Moon, scientists now think that the Moon’s more heavily cratered far side is that way because it actually gets bombarded more frequently than the near side.

From the paper’s abstract:

The Lunar Penetrating Radar (LPR) onboard Yutu-2 can transmit electromagnetic pulses to detect the lunar subsurface structure and properties of the regolith. The relative permittivity, loss tangent and TiO2+FeO content of lunar regolith materials at landing site are constrained with LPR data in this paper. The results indicate that the farside may be bombarded more frequently, leading to different regolith accumulation rates on the lunar nearside vs. farside. [emphasis mine]

The data was accumulated during the rover’s first five months on the surface, during those five lunar days. It found that the regolith at the landing site was about 39 feet thick, much thicker than found at the landing site for Yutu-1 on the Moon’s near side. The difference was partly expected because of the nature of the different locations, but combined with other factors the scientists concluded that a higher bombardment rate on the far side would also help explain the difference.

To put it mildly, this conclusion is uncertain. We only have one data point on the far side, and only a few more on the near side. At the same time, the conclusion is somewhat an example of science discovering the obvious. The very first images of the Moon’s far side, taken The Soviet Union’s Luna 3 lunar probe in 1959, showed the surface much more heavily cratered than the near side, with far less areas of smooth mare. Numerous mapping missions since have confirmed that impression.

And it is also intuitive to come to this conclusion. The near side always faces the Earth, which likely acts to intercept many of the type of meteorite hits that reach the Moon’s far side.

This conclusion however is still intuitive, and an honest scientist will not trust it. That this result from Yutu-2 appears to confirms it is therefore nice.

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Glacial flows covering a crater on Mars?

1:43 pm

Partially covered crater by glacial flows?

Cool image time! The photo to the right, cropped and reduced to post here, was taken on March 4, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows an eroded mound that appears to have flows coming off its north and south slopes that fill the surrounding low spots, including half-covering a nearby crater.

The science team for MRO’s high resolution camera chose this picture as their April 28th picture of the day, noting the following:

The objective of this observation is to examine a crater which seems to be in the process of getting covered by flow from a mound. This image, in Protonilus Mensae, may show us characteristics of the covering material: could it be debris-covered glaciers?

Below is a global map of Mars, with this mound’s location in Protonilus Mensae in the northern mid-latitudes indicated by a black cross.
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The big cliffs of Gediz Vallis on Mars

11:33 am

The Big Cliffs of Mt Sharp
Click for full image.

Cool image time! The photo to the right, cropped and reduced to post here, was taken on May 21, 2021 by Curiosity’s chemistry camera (ChemCam), normally designed to look at high resolution close-up imagery of nearby objects.

However, it can also be used as what the science team call “a long distance spyglass.” The image to the right is an example, looking at what I think are the distant but steadily approaching big cliffs on the western wall of the canyon Gediz Vallis. Make sure you look close at the shadowed cliff-face, probably several hundred feet high. It is filled with huge rock faces reminiscent of the most stark rock cliffs on the mountains of Earth.

The two images below provide the context, which makes the image even more quite breath-taking.
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