Tag Archives: geology

Tadpole on Mars

Tadpole on Mars
Click for full image.

Cool image time! The image on the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 7, 2019, and shows a crater on the northern fringe of Arabia Terra, one of the largest transitional regions between the Martian northern lowlands and the southern highlands. It shows a crater with an inlet canyon that makes the entire crater resemble a wiggling tadpole.

This is certainly not first tadpole-resembling crater found on Mars. See for example this press release from February 2018, showing a tadpole crater with the tail being an outlet channel. In today’s image however the channel feeds the crater.

In fact, take a look at the full image. This crater apparently occurred right at the edge of a large mesa cliff, with this impact cutting into the cliff near its bottom. The canyon might have actually existed before the impact, with the crater merely obliterating the canyon’s outlet.

If you look along that escarpment to the east you can see similar southwest-to-northeast flows. One is a canyon flowing downhill through the escarpment, probably resembling what the first canyon might have once looked like before the impact. To the east of this is another tadpole crater. This second tadpole impact however took place on top of the mesa, so the channel flows out from the crater and then down off the mesa, the reverse of the tadpole crater above.

These flow features are consistent with the nature of this transitional zone, a region with many features suggesting it was once the shoreline of an intermittent ocean. That ocean, if it had existed, is long gone, though scattered across the Martian surface are geological ghost features like these that speak of its past existence.


Martian dry ice frost on glacial remains?

Frost on ridgelines and inside crater
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Close-up of frost

Cool image time! The photo on the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on November 30, 2019. Located just east of Hellas Basin in southern mid-latitudes, the color strip shows dry ice frost both in the crater as well as on the ridgelines to the north. As noted in the caption, written by Candy Hansen of the Planetary Science Institute in Tucson, Arizona,

When we acquired this image, it was [winter in the southern hemisphere] on Mars, but signs of spring are already starting to appear at latitudes not far from the equator. This image of Penticton Crater, taken at latitude 38 degrees south, shows streamers of seasonal carbon dioxide ice (dry ice) only remaining in places in the terrain that are still partially in the shade.

The turquoise-colored frost (enhanced color) is protected from the sun in shadowed dips in the ground while the sunlit surface nearby is already frost-free.

Note for example how the frost disappears in the southern half of the crater floor, the part exposed to sunlight.

What immediately struck me however were the underlying features. The entire northeast quadrant of the crater’s rim appears to have been breached by some sort of catastrophic flow, as if there had been a glacial lake inside the crater that at some point smashed through suddenly, wiping that part of the rim out as it ripped its way through.

To the right is a full resolution inset, indicated by the white box above, of the dry ice frost on the outside of the crater. I find myself however drawn more to the underlying features, which once again have a chaotic aspect suggesting a sudden violent event, coming from the south and moving north.

I have no idea if my visceral conclusions here have any validity. At this latitude, 38 degrees, scientists have found a lot of buried inactive glaciers of ice, so I could be right. Or not. Your guess is as good as mine.


Gully on Mars

Gully in crater on Mars
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Cool image time! If we were told that the photo on the right was taken by an airplane over some southwest desert gully, no one should be surprised if we were to accept that description entirely. The gully sure looks like a lot of drainages one can routinely see when flying over the American southwest, dry, treeless, but showing the typical dendritic pattern seen for most desert water drainages.

Of course my readers all know that this is not in the American southwest, but on Mars, in a crater located in the transition zone between the southern highlands and the northern lowland plains. The image, cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on October 12, 2019.

It appears that this particular gully has been subject to repeated monitoring, since November 2015. A rough and very quick comparison of the earlier image with today’s image does not show any obvious change. This does not mean there hasn’t been any evolution, as my look was cursory, and I could easily be missing changes. Seasonal variations might also be occurring that I could be missing.

The reasons for the monitoring are of course obvious. This gully strongly suggests the flow of liquid downhill. Is that occurring today, or are we seeing the evidence of a past flow from long ago? Only some long term monitoring can tell.

There is also the possibility that we are looking at a buried glacier. The crater is located at 42 degrees north latitude, well within that mid-latitude band where scientists have located many buried Martian glaciers. If so, then the monitoring is to see if that glacier is active in any way.


Stardust found in meteorite older than Earth

Scientists studying what they think is grains of stardust in a meteorite the hit the Earth in 1969 have discovered the oldest material ever found on Earth, material that is actually older than the Earth itself.

The meteorite, dubbed the Murchison meteorite after the nearest city in Australia where it landed, has been a treasure trove of information for planetary scientists because so much of it was recovered right after impact.

About 30 years ago it was found that the rocks housed “presolar grains” – tiny grains of silicon carbide older than the Sun. But their exact age hadn’t been determined until now.

To figure that out, the researchers on the new study measured how long these presolar grains had been exposed to cosmic rays. These high-energy particles flit around space and can pass through solid matter, creating new elements inside the existing minerals as they interact with them. That means the scientists can measure the amount of these new elements in the grains to determine how long they were floating around in space – and, ultimately, how old they are.

In doing so, the team found that most of the grains were between 4.6 and 4.9 billion years old. The Sun itself is at the younger end of that range, at 4.6 billion years old, while the Earth didn’t form until 4.5 billion years ago.

But the oldest of the grains were dated to more than 5.5 billion years, making them the oldest known material on Earth. The team says that the history of these grains could be traced back even further, to the stars that birthed them some 7 billion years ago. According to the researchers, this finding suggests that our galaxy went through a period of intense star formation around that time.

Obviously there are uncertainties with this result, though their age estimates are quite reasonable and largely robust.


Curiosity climbs a hill

Overview map of Curiosity's journey through sol 2643

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

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

Since my last Curiosity update on November 6, 2019, the science team has sent the rover climbing up what they call Western Butte, the butte directly to the west of Central Butte and part of the slope/escarpment that separates the clay unit from the Greenheugh Piedmont and the sulfate unit above that.

The overview map to the right gives a sense of the journey. The thick yellow line indicates its route since it climbed up from the Murray Formation onto Vera Rubin Ridge in 2017. The thick red line indicates their planned route, which they have only vaguely been following since their arrival in the clay unit.

Below the fold are two panoramas that I created from a sequence of images taken by Curiosity’s left navigation camera from the high point on Western Butte, the first looking north across the crater floor to the Gale Crater rim approximately 30 miles away and indicated by the thin yellow lines on the overview map. The second looks south, up hill towards Mount Sharp, and is indicate by the thin red lines.
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Pedestal craters in the Martian northern lowlands?

Pedestal craters on Mars?
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Cool image time! The photo on the right, cropped and reduced to post here, shows a cluster of really strange mesas, craters, and pits, located in Utopia Planitia, the largest and deepest plain of Mars’ northern lowlands where an intermittent ocean might have once existed.

The image was taken on October 26, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) as part of its regular image-taking program. In this case it was dubbed a “terrain sample” image, meaning that it was not specifically requested by any researcher, but was taken because they need to use the camera regularly to maintain its temperature, and thus sometime produce images over previously untouched areas, not knowing what they will find, as part of that maintenance schedule.

In this case the terrain sampled is especially intriguing. Are the upraised depressions what are called pedestal craters, created when the impact landed on what was once an icy plain, which subsequently sublimated away to leave the crater sitting high above the surrounding flats? Maybe, but this location is at 23 degrees north latitude, and research has generally found these pedestal craters at latitudes higher than 30 degrees.

Moreover, that many of these upraised depressions are not circular suggests that their formation was not impact related.

Other mysteries: Why are all the ridgelines bright? What caused the parallel white streaks to the east and west of some mesas? And if these are impact craters, why are some distorted?

If this region was once the seabed of an intermittent ocean, this fact might explain the features. Then again, it is more likely that this lowland area was once covered in ice in the far past, when the planet’s tilt was greater and the lower latitudes were actually colder than the polar regions, and thus allowed ice to build up in those lower latitudes. We might therefore be seeing the end result of an erosion/sublimation process as that ice disappeared when Mars’ inclination shifted.

Lots of questions, and no answers.


Yutu-2 completes 13th lunar day

China’s Yutu-2 lunar rover and its lander Chang’e-4 have completed their thirteenth lunar day on the far side of the Moon and have been placed in sleep mode.

During the twelve lunar day the rover traveled about 12 meters, or about 40 feet.

The rover has found materials from deep inside the moon that could help unravel the mystery of the lunar mantle’s composition and the formation and evolution of the moon and the earth. Using data obtained by the visible and near-infrared spectrometer installed on Yutu-2, Chinese scientists found that the lunar soil in the landing area of the Chang’e-4 probe contains olivine and pyroxene which came from the lunar mantle deep inside the moon.

Due to the complicated geological environment and the rugged and heavily cratered terrain on the far side of the moon, the rover drives slowly but steadily and is expected to continue traveling on the moon and make more scientific discoveries.


Darkened craters on Mars

Darkened craters on Elysium Planitia
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It’s time for the first cool image of 2020! The photo to the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 10, 2019. It shows a handful of darkened craters on the vast volcanic Elysium Planitia plain between the giant volcanoes Olympus Mons to the east and Elysium Mons to the north.

My first thought was that these dark craters were recent crater impacts, possibly a set of secondary impacts from a larger nearby impact. However, in looking at the archive of MRO’s high resolution camera at this location (Latitude 5.925° norther; Longitude 164.965°) I found that almost no high resolution images have been taken in this region, as shown by the overview map below to the right.
» Read more


Giant scallops on Mars

Scallops on Mars
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It’s a slow news week, with the too much partying only real space news today the expected third launch of China’s Long March 5 rocket (supposedly scheduled for this morning but so far no word). (To my gentle reader: For some reason I have been losing a day during this whole week, always thinking that Christmas was on Thursday and that today was Friday. Thus my error in thinking the Long March 5 flight was today. It is tomorrow morning. Forgive me for my absent-mindedness.) So let’s look at a cool image!

The photo on the right, cropped and reduced to post here, was taken my the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 8, 2019. Entitled “Scalloped Depressions in Utopia Planitia,” it shows a strangely eroded surface in the northern lowlands of Mars, where an intermittent ocean might have once existed.

The location of these scallops is shown to the right.

Location of scallops in Utopia Planitia

I have taken the same overview map used from two recent cool image posts, showing how these scallops relate in location to the strange crater in Utopia Planitia as well as the glacial-surrounded mesa in Protonilus Mensae.

In caves, scallops like this form from water or wind flow, but when they do, they are all oriented the same way. Here the scallops are at different orientations, terracing down from the center of the image. In this case it appears that scientists believe [pdf] the formation process is related to the sublimation of underground ice at this location.

According to [one hypothesis] scallop formation should be ongoing at the present time. Sublimation of interstitial ice could induce a collapse of material, initially as a small pit, then growing southward because of greater solar heating on the southern side. Nearby scallops would coalesce together as can be seen to have occurred.

What is most cool is that the geologists think the process that forms these scallops is related to the same processes that cause the formation of the swiss cheese landforms in the south polar regions.


Crater in the Martian northern lowlands

Crater in Utopia Planitia
Click for original full image.

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 October 26, 2019. It shows a crater in the western edge of Utopia Planitia, the largest and deepest region of the Martian northern lowlands where it is theorized that an intermittent ocean might have once existed.

My first uneducated guess at looking at this image is that the impact occurred in some sort of wet slushy mud or ice, which then melted and filled the crater interior, ponding in the crater’s center as it froze.

A more educated guess, based on what I have learned in the past year, is not much different. The crater is located at 40 degrees north latitude and therefore sits in the middle of the mid-latitude band where scientists think there are a lot of buried inactive glaciers.

Overview map

The map to the right, revised from my December 20, 2019 post about glaciers flowing off the slopes of a mid-latitude mesa, illustrates this even more clearly.

This crater, indicated by the white cross, sits at approximately the same latitude as that mesa and its glaciers in Protonilus Mensae. It also sits at in an area where accumulated data from several spacecraft have mapped a lot of water ice, close to the surface.

Thus, it is reasonable to suppose that the impact that made this crater pushed into that ice-table, melting the water which subsequently froze and then subsided downward into the ground to form the crater’s central ponded features.

Or to put it as I did initially, the impact smashed into some wet slushy mud/ice, melting it so that it filled the crater interior to then freeze as we see it.


A deep dive into Valles Marineris

Dunes on the floor of Valles Marineris
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The vastness of Mars is sometimes hard to fathom. While the planet is much smaller than Earth, its entire global surface is approximately the same as the Earth’s land area. This is a lot of territory. It took humanity many tens of thousands of centuries to expand outward to settle all of it. It took even longer before humanity was successfully able to map all of the Earth so that its entire surface was known to all humans, a task that was only completed a handful of centuries ago.

While we now have the technology to quickly map the entire globe of a planet like Mars, the devil is always in the details. At this time the resolution of our global maps give us only a glimpse of the Martian surface.

The image to the right, reduced and cropped to post here, is a good example. Taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 30, 2019, it shows a set of large dunes on the northern floor of a side canyon on Mars that is part of Coprates Chasma, a canyon that forms only a small part of the vast Valles Marineris canyon system east of the giant volcanoes of the Tharsis Bulge.

The sand of these dunes is mostly volcanic material, dark basalt that was deposited as lava from those giant volcanoes, then later ground down in landslides and erosion to be recycled as sand that formed dunes trapped within the canyon bottom. The dunes themselves are slowly moving eastward, driven mostly by the predominate west-to-east winds that blow down this side canyon of Coprates Chasma. The motion is very slow, so slow that even though the image title is “Coprates Chasma Dune Changes”, I was unable to spot any changes when I compared this 2019 image with a photo taken in June 2019.

To find out what had changed, I contacted Matt Chojnacki of the Lunar and Planetary Laboratory at the University of Arizona, who has been studying the nature of the sand dunes in Valles Marineris. After making a quick preliminary blink test using more sophisticate tools than I have available, he found “minor advancements. The rocks move a bit too in places.” Without a full analysis he also added, “I can tell some dune crests have moved to the east.”

The research by Chojnacki and others has found that the dunes within Valles Marineris are in many ways different than dunes found elsewhere in the mid-latitudes on Mars, suggesting that being trapped within this giant canyon has produced some specific regional features. They tend to be darker, the canyon contains several sand dune seas, called ergs (only seen elsewhere on Mars in the polar regions), and the dunes tend to be more hardened, so that they change relatively little when compared to similar dunes elsewhere on Mars.

These particular dunes in Coprates Chasma however are not hardened, since if so they would have been covered by the landslides and material that comes down from the canyon’s nearby northern slopes. Instead, they move, but appear to move far slower than similar dunes elsewhere on Mars.

To me, this image provides a good vehicle for getting a sense of the size of Valles Marineris. Coprates Chasma itself only one of about a dozen named sections of the entire Valles Marineris canyon system, and this particular image shows only the floor of a side canyon of Coprates. The map below gives an overview of the entire system.
» Read more


Megadunes in the giant canyon of Mars’ north polar icecap

Martian megadunes at the beginning of summer
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Cool image time! The photo to the right, cropped and reduced to post here, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on September 15, 2019, right at the beginning of summer at the north polar icecap of Mars.

Without a larger context it is very difficult to figure out what this image shows. The image title, “Seasonal Changes of Chasma Boreale Megadunes,” gives us some basic clues. The streaks of black and dark grey are giant dunes, with this image showing their trailing edge. The darkest streaks are likely places where the thin winter mantle of dry ice has begun to sublimate away with the coming of spring, exposing the darker sand dunes below. The surrounding flat white areas are either the permanent water ice of the icecap or the surface of the lowland northern plains that surround that icecap.

The montage below shows a series of monitoring photos, beginning in 2018 during the last Martian summer and continuing through the start and middle of the spring and ending with the photo above. It shows the seasonal evolution of that upper carbon dioxide dry ice mantle, which reveals the darker dunes below as that dry ice mantle sublimates away.
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A crack in the Martian crust

Crack in the Martian crust
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Cerberus Fossae

The photograph to the right, reduced and cropped to post here, was imaged on October 20, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a spectacular thousand-foot-deep canyon in the region of Cerberus Fossae, an area of Mars crossed by numerous deep east-west fissures and depressions.

Hidden in the small white box on the eastern end of that canyon are Martian geological features, small and at first glance not that interesting, that are of great significance and the focus of intense research.

The map to the right shows an overview of the region. The yellow cross shows the location of this particular crack.

In my previous post about Cerberus Fossae, I had incorrectly assumed that these cracks and similar lines of pits or depressions were caused by the sinking of surface material into underground lava tubes. While this is possible in some cases, it is not the main cause of these cracks. Instead, they were formed due to the pressure from below caused by the rise of the surrounding giant volcanoes, Elysium Mons to the north and Olympus Mons to the east. That pressure stretched the crust until it cracked in numerous places. In Cerberus Fossae this produced a series of parallel east-west fissures, some more than seven hundred miles long.

The young age of Cerberus Fossae is dramatically illustrated by the wider mosaic below, showing the entire crack.
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Martian “What the heck?” formations

What the heck caused these?
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Cool image time! In digging through the new images that come down from the high resolution camera on Mars Reconnaissance Orbiter (MRO), my reaction sometimes is “What the heck caused that?”

That was my reaction when I looked at the image to the right, cropped to post here.

The full image, taken on October 6, 2019, shows the floor of one of the many north-south fissures found in the volcanic Tharsis Bulge west of Valles Marineris and east of Olympus Mons. The fissures are caused when the crust is pushed upward by volcanic pressure, causing the surface to crack.

In this case the mystery is that patch of east-west ridges at the bottom of this somewhat wide fissure. While they might be dunes, they do not resemble dunes, as they have a rigid and somewhat sharp appearance. More puzzling is their somewhat abrupt appearance and disappearance. Except for its northern end, the edges of the patch are so sharply defined. If these were dunes you’d think they’d fade away more gradually.

Could the ridges be a more resistant subsurface feature slowly being revealed as surface material erodes away? Sure, but their orientation is completely opposite to the north-south fissures that dominate this region. One would expect deeper features to reflect that same general orientation. These ridges do not.

This image was dubbed a “Terrain Sample,” which means it was taken not because of any specific research goal, but because the scientists who run MRO’s high resolution camera had a gap in their schedule and needed to take a picture to maintain the camera’s proper temperature. In such cases they often take somewhat random images, not knowing what they will find. In this case they struck geological gold, a mystery that some postdoc student could spend a lot of time analyzing.


Mars Express confirms ancient glaciers in northern Martian mid-latitudes

Perspective view of Deuteronilus Mensae
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The European Space Agency’s orbiter Mars Express has confirmed the presence of large fractured ice sheets suggestive of buried and ancient glaciers. These ice sheets are within one region on Mars located in the mid-latitudes where many such glacial features have been found. They are also in the transition zone between the northern lowlands and the southern highlands.

This landscape shows clear and widespread signs of significant, lasting erosion. As is common with fretted terrain, it contains a mix of cliffs, canyons, scarps, steep-sided and flat-topped mounds (mesa), furrows, fractured ridges and more, a selection of which can be seen dotted across the frame.

These features were created as flowing material dissected the area, cutting through the existing landscape and carving out a web of winding channels. In the case of Deuteronilus Mensae, flowing ice is the most likely culprit. Scientists believe that this terrain has experienced extensive past glacial activity across numerous martian epochs.

It is thought that glaciers slowly but surely ate away at the plains and plateaus that once covered this region, leaving only a scattering of steep, flat, isolated mounds of rock in their wake.

Smooth deposits cover the floor itself, some marked with flow patterns from material slowly moving downhill – a mix of ice and accumulated debris that came together to form and feed viscous, moving flows of mass somewhat akin to a landslide or mudflow here on Earth.

Studies of this region by NASA’s Mars Reconnaissance Orbiter [MRO] have shown that most of the features seen here do indeed contain high levels of water ice. Estimates place the ice content of some glacial features in the region at up to 90%. This suggests that, rather than hosting individual or occasional icy pockets and glaciers, Deuteronilus Mensae may actually represent the remnants of an old regional ice sheet. This ice sheet may once have covered the entire area, lying atop the plateaus and plains. As the martian climate changed this ice began to shift around and disappear, slowly revealing the rock beneath.

Overall, the data coming from both Mars Express and MRO increasingly suggests that there is a lot of buried glacial ice in the mid-latitudes. Mars might be a desert, but it is increasingly beginning to look like much of the planet is a desert like Antarctica, not the Sahara.


Mid-latitude Martian glacier?

Glacier on Mars?
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Cool image time! I have posted a lot of Mars photographs in the past few months showing possible glaciers in the mid-latitudes of Mars, where scientists think they have identified a lot of such features. Today is another, but unlike many of the previous examples, this particular feature more closely resembles a typical Earth glacier than almost any I have so far posted.

Based on the image’s title, “Lineated Valley Fill in Northern Mid-Latitudes,” given by the science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO), I suspect that it remains unproven that these are features of buried glacial ice. Thus, they use a more vague descriptive term, lineated, to avoid pre-judging what these features are.

Nonetheless, a glacier is sure what this lineated valley fill looks like. See for example the Concordia confluence of two glaciers in the Karakoram Mountains of Pakistan, near the world’s second highest mountain, K2. Though obviously not the same, you can see many similarities between this Martian feature and Concordia.

MRO has taken only three photographs of this particular valley, with one image useless because it was taken during a dust storm. Yet, the other good image, farther downstream in this valley, shows very similar features.

The valley itself is formed from chaos terrain, located in the transition zone between the southern cratered highlands and the flat northern lowlands where a possible intermittent ocean might have once existed. Thus, for buried ice to be here is quite possible.


Sinkholes galore!

Sinkholes galore south of Olympus Mons
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Cool image time! The photograph to the left, cropped to post here, was part of the November image dump from the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a wind-swept dusty plain trending downhill to the west that is filled with more than a hundred depressions or sinkholes.

Unlike other pit images I have posted previously, this one is not focused on one particular pit or a string of pits. Instead, what makes it interesting is the large number of pits, scattered across the terrain in a random pattern. Their random distribution suggests that they are unrelated to any specific underground feature, such as a lava tube. Instead, some aspect of the underground geology here is causing the ground to sink at random points.

Below is an overview map showing where this dusty pit-strewn plain is located, indicated by the blue cross.
» Read more


Recent impact on Mars

Recent impact on Mars
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Cool image time! While finding recent impacts on Mars is not that unusual, the image to the right, found among the November image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO), was dramatic enough that I decided that more people besides planetary scientists should see it. For scale the photograph is exactly 500 meters wide.

The photograph, taken September 26, 2019, also illustrates all the typical aspects of impact craters, and how they change the landscape.

This impact took place sometime between July 17, 2012 and January 4, 2018. We know this because it wasn’t there in a low-resolution image taken by the wide angle survey camera on MRO on the first date but was there when that same camera took another picture on the second date. Below is a side-by-side comparison of that July 17, 2012 image with the high resolution 2019 image above.
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First global geologic map of Titan

Global geologic map of Titan
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Planetary scientists today released the first global geologic map of the Saturn moon Titan. The image on the right is a reduced version of the full image.

In the annotated figure, the map is labeled with several of the named surface features. Also located is the landing site of the European Space Agency’s (ESA) Huygens Probe, part of NASA’s Cassini mission.

The map legend colors represent the broad types of geologic units found on Titan: plains (broad, relatively flat regions), labyrinth (tectonically disrupted regions often containing fluvial channels), hummocky (hilly, with some mountains), dunes (mostly linear dunes, produced by winds in Titan’s atmosphere), craters (formed by impacts) and lakes (regions now or previously filled with liquid methane or ethane).

To put it mildly, there is a lot of uncertainty here. Nonetheless, this is a first attempt, and it shows us that the distribution of these features is not homogeneous. The dunes favor the equatorial regions, the lakes the polar regions. Also, the small number of craters could be a feature of erosion processes from the planet’s active atmosphere, or simply be because Cassini’s radar data did not have the resolution to see smaller craters. I suspect the former.


Islands of ice on Mars and Pluto

Ice-filled craters near Martian south pole

In a paper published today in the Journal of Geophysical Research: Planets, scientists describe the identification of 31 ice-filled craters in the high southern latitudes of Mars. The map to the right, from their paper, shows the locations of these craters. The scientists also took a look at Pluto, and found five craters there that had similar features, though these were likely filled with frozen nitrogen, not water ice.

From their abstract:

These new 31 ice deposits represent an inventory of more than 10 trillion cubic meters of solid water, similar to but greater in number and volume than previously studied features near the north pole. Similar features of nitrogen ice may exist in craters on Pluto, suggesting that craters are a favorable location for the accumulation or preservation of ices throughout the Solar System. [emphasis mine]

These results are reinforced by the existence of glacial features found in numerous Martian craters at much lower latitudes, as well as the ice suspected to exist in the permanently shadowed craters on the Moon and Mercury. The processes that put the ice there on these different planets might be fundamentally different, but the results are the same: Ice accumulating within craters.

One aspect of these high latitude craters that remains somewhat unexplained is their asymmetrical distribution around the south pole, favoring the side of the planet south of Mars’ giant volcanoes. Moreover, in looking at the ice deposits within these craters the scientists found that the ice seemed to lie off-center within the craters, favoring a similar direction.

Based on the available data, the scientists theorize that the most likely cause of this asymmetric off-center pattern is wind. From their paper:

Basic physical arguments, mesoscale atmospheric models, and geomorphological observations predict deflection of winds emanating from the south pole by the Coriolis Force. Such deflection results in a general westward trend of winds (i.e., easterlies) in the south polar regions outside the [south pole cap], matching the [ice-filled crater] offsets we observe.

This correlation implies that wind is important in … formation and/or evolution [of craters with ice]. For the case where winds control [their] formation, katabatic winds may travel down the east side of crater walls and preferentially deposit ice on the west side of the crater via orographic precipitation as they flow up the west crater wall. This mechanism thus favors local accumulation of ice within craters.

I find it fascinating that the location of ice within craters on Mars might indirectly provide scientists with information about the planet’s global weather patterns. This unexpected connection highlights the need to dismiss no data or feature in trying to understand planetary formation. Unlikely things might answer our questions.


A journey into the depths of Valles Marineris

Valles Marineris

Cool image time! Rather than start with the cool image, let’s begin with the long view. To the right is a wide mosaic of Valles Marineris on Mars, the largest known canyon in the solar system. About 2,500 miles long and 400 miles wide, this canyon is so large that it would cover most of the United States if put on Earth. The Grand Canyon, 500 miles long by 19 miles wide, could easily fit within it and not be noticed. In depth Valles Marineris is equally impressive, with a depth of more than four miles, about four times deeper than the Grand Canyon.

A closer view of the central regions of Valles Marineris

The white cross in the mosaic above is where we are heading. You can see it as the white box in the zoomed in overview to the right. This central part of Valles Marineris is named East Melas Chasma, and the red boxes indicate locations where the high resolution camera of Mars Reconnaissance Orbiter (MRO) has already taken images.

As you can see, we do not yet have many high resolution images of this part of the canyon floor. The white box is the most recent image, and is the subject of today’s post.
» Read more


Polygons on Mars

Scallops and polygons on Mars
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Cool image time! The photograph on the right, cropped to post here, was taken on September 25, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and made public in its November image release. It shows the weird but very typical scalloped terrain, with its adjacent polygon pattern of fractures, found routinely in the northern lowland plains of Utopia Planitia on Mars. From an earlier captioned image from 2006 of these same features:

The scalloped depressions are typical features; a smooth layered terrain located between 40 and 60 degrees in both hemispheres. Scalloped depressions probably form by removal of ice-rich subsurface material by sublimation (ice transforming directly from a solid to a gaseous state), a process that may still be active today. Isolated scalloped depressions generally have a steep pole-facing scarp and a gentler equator-facing slope. This asymmetry is interpreted as being the result of difference in solar heating. Scalloped depressions may coalesce, leading to the formation of large areas of pitted terrain.

The polygonal pattern of fractures resembles permafrost polygons that form in terrestrial polar and high alpine regions by seasonal-to-annual contraction of the permafrost (permanently frozen ground). On Earth, such polygons indicate the presence of ground ice.

On Earth these polygons are most often seen in mud, usually suggesting a drying process where the ground contracts with the lose of fluid. On Mars the cracks probably also form from contraction, but not by the lose of fluid but the lose of water ice as it sublimates into a gas.

These polygons and scallops illustrate an important feature of Mars’ vast northern plains. On large scales these plains appear flat and featureless. Up close however many many strange features, like the polygons and scallops in this image, come into view.
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Mars’ seasonally vanishing carbon dioxide polar cap

Buzzell dunes, March 19, 2019
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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

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
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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

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.


Ancient glacier flows on Mars

Ancient glacial flow in Euripus Mons
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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

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.


Big landslides on Mars might not require ice

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.


Bhabha Crater at dawn

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.


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

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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