Tag: Mars

A Martian crater with a straight edge

10:02 am

A mis-shapened crater on Mars
Click for full image.

Cool image time! The image to the right, cropped and reduced to post here, was released today by the science team of the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small Martian crater whose northern rim for some reason is flattened into a straight line. Such a crater is rare, since almost all craters rims are round, even in the case of a low angle impact. The cause is unknown, though there are theories. From the caption, written by Ingrid Daubar of the Lunar and Planetary Laboratory in Arizona:

One possibility is that there was a zone of joints or faults in the crust that existed before the impact. When the impact happened, the crater formed along the straight line of these faults. Something similar happened to Meteor Crater in Arizona. Our image doesn’t show any faults, but they could be beneath the surface.

Perhaps some sort of uneven collapse changed the shape of the crater. There are piles of material on the crater’s floor, especially in the northwest and northeast corners. If those piles fell down from the rim, why did it happen there and not in other places? This crater is near the size where larger craters start to show wall slumping and terraces, so this type of collapse could be occurring unevenly.

The crater is located in the southern cratered highlands of Mars, at about 32 degrees latitude. At that latitude, it is also possible that some past glacial activity could have misshapen this crater, though I have no idea how. The crater itself does not appear to have any glacial material in it.

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Weird central peak in Martian crater

3:14 pm

Textured central peak in Martian crater
Click for full image.

Cool image time! The photo to the right, cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on March 18, 2020. It shows a very strange central peak in a crater on Mars. Not only does this peak stick out like a sore thumb in a relatively flat crater floor, its surface is strangely textured, patterned with what look like scallops.

The overview map below shows the area covered in the crater by the full image.

My guess is that the peak is the final impact melt from the original impact. Think of a pebble thrown into a pond. You get ripples (the crater rim) as well as an upward drop of water (the central peak). Unlike pond water, the material in a crater freezes quickly, leaving both the ripple and the upward drop frozen in place.

Close overview of crater

This peak however also reminds me of volcanic cones found in the American southwest, the remnant cone of a much larger volcano that has long ago eroded away.

The textures might be evidence of that erosion process, as they resemble scallops that wind and water erosion can cause on rock faces.

We also could be seeing dunes on the slopes themselves, though I think this is unlikely. This crater is on the edge of the vast Medusae Fossae Formation, the largest volcanic ash deposit field on Mars, as shown by the white cross on the overview map below. Thus, being on the edge of this ash field there is a lot of available dust and sand that can pile up on these slopes.

Wide Overview map

Still, the sunlight side of the ridge suggests the scallops are in bedrock, not sand dunes. And to assign their origin to either wind or water or ice erosion I think is a stretch.

So while the peak is probably the frozen melt remains of the original impact, the scallops are a geological mystery that needs unraveling.

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Amazing layers

11:07 am

Bedrock layering in Holden Crater
Click for full image.

Cool image time! The science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) today released a cool captioned image entitled “Exquisite Layering”, showing a place on the floor of Holden Crater where the dust and sand that normally covers most of the Martian surface has been wiped away, cleared off because these layers are on higher sloping terrain.

The image to the right, cropped to post here, focuses in on that exposed layering, believed to be sedimentary and must have therefore happened in the eons following the impact that caused the crater.

Overview map

The overview map to the right shows with the red box the location of this layering inside Holden Crater. The map also illustrates why this crater was considered a candidate landing site for Curiosity. Like Gale Crater, it has evidence — the large meandering canyon system flowing into the crater — that suggests it had once been filled with a water lake. These sedimentary layers support that hypothesis, suggesting that this lake was intermittent. Each time it refilled and then dried up, it laid down a new deposit of those sedimentary layers.

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Launch date for UAE’s Hope Mars orbiter set

9:27 am

The new colonial movement: Japan and the United Arab Emirates (UAE) have set the launch date for UAE’s Hope Mars orbiter, now scheduled for July 15 with a launch window that closes on August 13.

If all goes well it will enter Mars orbit in February 2021.

The probe is a UAE project in name only. Much of it was built in the U.S. by U.S. companies, working with UAE engineers and scientists. It is also being launched by Japan.

Regardless, the training and knowledge obtained by those UAE engineers and scientists is the real point of the mission. The UAE wants to diversify its economy away from oil, and it is trying to use the excitement of space exploration to do it. It hopes these engineers and scientists will use what they learned to come up with new projects that in the future will be built entirely in the UAE.

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More pits found on Mars

3:04 pm

Pit near Hephaestus Fossae
Click for full image.

Overview map

Since 2018 I have made it a point to document every new pit image taken on Mars by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The list of can be found at the bottom of this post.

In the most recent release from MRO, a number of new pits were photographed. All continue to suggest that Mars has a lot of underground voids, some caused by lava flow, some by tectonic activity, some by water ice erosion, and some almost certainly caused by processes we don’t yet know. The images also suggest that we have only identified a small fraction of those underground voids.

The first image to the right, cropped to post here, shows the one new pit in the northern lowlands of Utopia Planitia, near a series of meandering channels and canyons dubbed Hephaestus Fossae and Hebrus Valles.

This appears to be the fifth such pit found in this region. Previously I had documented the first four. The overview map to the right adds this fifth pit. Note how the pit is much closer to the head of Hephaestus. In the full image you can see fissures both to the north and south, as well as many nearby aligned depressions, suggesting the existence of more underground passages, some possibly linked to voids under this very pit.

The pit itself seems filled, with no apparent side passages, though to the southwest there might be something leading off in the shadows.

The overall terrain in this region, including these pits, the fissures, and the many aligned depressions, strongly suggests a lot of underground voids. As I noted in 2019:
» Read more

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A shadowed ice patch on Mars

1:26 pm

A shadowed ice patch on Mars
Click for full image.

Cool image time! The evidence coming back from Mars in the past two decades has increasingly suggested that there is a lot of water in that planet’s mid- and high latitudes. In the mid-latitudes the evidence suggests that ice is locked in a lot of buried and inactive glaciers that were laid down during periods when the planet’s rotational tilt, its obliquity, was greater so that the annual seasons were more extreme. During those times the mid-latitudes were colder than the poles, and water was being transferred from the poles to those mid-latitudes.

The image to the right appears to be more such evidence. Taken on March 21, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and cropped and brightened by me to bring out the important details, it shows what looks to be a distinct patch of ice on the south-facing slope of the rim of a large crater. Since this crater is in the southern mid-latitudes (34 degrees south), that south-facing slope generally gets much less sunlight, even in the summer, so any remaining buried glacial ice on that slope will linger for a longer period.

Think of the lingering ice and snow patches on shadowed locations on Earth. Because the Sun does not directly shine on them, they will be the last patches to melt away.

What I think is likely important about this patch are the exposed layers along its edge. These are the spots that are melting first, as they are where the ice is exposed, unprotected by a layer of dust and debris. It is also here that we have a window into that geological history. Even at this resolution you can see that the ice was laid down in layers, meaning that it contains evidence of those repeated climate cycles produced by Mars’ shifts in obliquity.

Those layers even seem to show the same sharp and sudden change from brighter and dirtier layers, as seen in the layers of the north pole ice cap, that occurred about 4.5 million years ago.

How tantalizing. The entire climate history of Mars is sitting there for us to decipher. We need only drill a few core samples and voila! the pieces of that history will start to fall into place.

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The edge of an eroded buried Martian glacier

12:55 pm

The edge of an eroded buried Maritian glacier
Click for full resolution image.

Overview

Cool image time! The image to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on April 6, 2020.

The image shows the dying edge of a debris flow coming down from a mesa, the edge of which can be seen as the dark slopes in the upper left. The white arrows point up slope. It is located in the chaos terrain of a mid-latitude region called Deuteronilus Mensae, in the transition zone between the southern highlands and northern lowlands, where many such glacial-like features are found. I featured a similar nearby glacial edge only two months ago, where the image showed the glacier’s break up and collapse at its edge.

Here, the debris flow isn’t breaking up so much as crumbling away, its edge a line of meandering depressions, with the uphill slope covered with many knobs and tiny depressions, reminiscent to me of the many features I see in caves, where the downward flow of water shapes and erodes everything to form cups and holes and knobs, all the same size. If you click on the full resolution image and zoom into that debris slope and then compare it with the linked cave formation photo, you will see the resemblance.

We are almost certainly looking at a buried inactive glacial flow coming off that mesa, though it appears to be eroding at its foot. The overview image to the right shows the context, with the red dots indicating this image as well as similar features in adjacent mensae regions (featured in the linked images above). While the chaotic and rough terrain found along this transition zone does not make them good first settlement sites, the ample evidence of vast reservoirs of buried ice, combined with a variety of topography, will likely someday make this good real estate for those living on Mars.

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The blobby wettish flows of Mars

12:21 pm

flow-like feature in Utopia Planitia
Click for full image.

Cool image time! Rather than talk about shut downs, lying politicians, and our tragically fear-filled society, let’s go exploring on Mars. The image to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on February 8, 2020. Dubbed a “Flow-Like Feature within the Adamas Labyrinthus”, it shows what appears to be a very distorted and eroded pedestal crater surrounded by strange triangular-shaped flow features.

It also shows, as does much other research, that the northern mid-latitudes of Mars have a lot of frozen water, much of it buried very close to the surface.

Assuming this is a pedestal crater (which it might not be), this feature has to be very old. Pedestal craters require age, as to stand out above the surrounding terrain a lot of time is needed to erode that terrain away. This age is confirmed by the bunch of newer craters on top.

At the same time, the partially filled small crater near its bottom, as well as the soft eroded depressions on top, suggest that much of this surface has been reshaped by more recent flows, changing its shape over time.

The surrounding triangular flows probably occurred at the original impact, and suggest that there is ice near the surface, making the material here act almost like wet mud when heated. Since this location is right in the middle of the mid-latitude bands where scientists have found lots of evidence of buried glaciers and ice near the surface, this supposition seems reasonable.

The overall location provides some further context.
» Read more

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The salty liquid water on Mars

9:49 am

Map of seasonal salty liquid water on Mars
Click for full unannotated image.

The map above, reduced and annotated by me, comes from a new science paper that has attempted to model where on Mars we might find liquid very salty water, based on the planet’s known temperature and make-up. From the press release:

The team of researchers used laboratory measurements of Mars-relevant salts along with Martian climate information from both planetary models and spacecraft measurements. They developed a model to predict where, when, and for how long brines are stable on the surface and shallow subsurface of Mars. They found that brine formation from some salts can lead to liquid water over 40% of the Martian surface but only seasonally, during 2% of the Martian year.

“In our work, we show that the highest temperature a stable brine will experience on Mars is -48°C (-55° F). This is well below the lowest temperature we know life can tolerate,” says Dr. Rivera-Valentín. “For many years we have worried about contaminating Mars with terrestrial life as we have sent spacecraft to explore its surface. These new results reduce some of the risk of exploring Mars,” noted Dr. Alejandro Soto at the Southwest Research Institute and co-author of the study. [emphasis mine]

I have added a red rectangle to the map, showing the candidate landing zone for SpaceX’s Starship. This paper illustrates again that this choice is a good one. We know from other research that there is a lot of ice very close to the surface here. This research indicates that for a little less than one percent of each year, some of that ice will turn to liquid brine.

Whether it will be easier to process the ice or the brine into drinkable water remains unknown. This location however will give future colonists that option.

That this model also suggests that there is little risk of contaminating Mars accidently with terrestrial life is really not a surprise. All the research of Mars for decades has found that it is inhospitable to terrestrial life. This data however is further confirmation, and tells us once again that worrying about contaminating the planet is a irrelevancy. For scientific reasons some precautions should be taken, but to spend a lot of time and money sterilizing the spacecraft we send there will be a fool’s errand. For humans to settle Mars will require a very very high level of engineering and adaptation, something we humans are very naturally good at, but something that shouldn’t be burdened with unnecessary tasks or restrictions.

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A relaxed crater on Mars

12:40 pm

A relaxed crater on Mars
Click for full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, shows what the science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) call a “Relaxed Crater.” This particular image was taken in July 2014. A more recent photo was taken in March 2020 to create a stereo pair, but because this older image shows more of the crater I decided to highlight it.

The crater is considered relaxed because it is very shallow and appears as if, after impact, some process caused the interior to in-fill with material even as the rim became less pronounced and degraded (as explained in this paper [pdf]). The process could have involved either molten magma or melted ice. As this crater is located in the northern highlands to the southwest of Erebus Mountains, in a region that research has consistently suggested has a great deal of ice just below the surface, the latter seems likely. This assumption is further reinforced in that the crater is also located in the mid-latitudes where scientists have found a lot of craters they think are filled with buried glaciers. This certainly seems the case here.
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UAE’s Mars probe arrives in Japan for launch in July

9:31 am

The new colonial movement: The United Arab Emirates’ (UAE) Mars orbiter, dubbed Hope, has arrived at its launch site in Japan in preparation for its July launch on a Mitsubishi H-2A rocket.

Previously I had thought the probe had been built in the UAE with help from engineers from India, but that was not the case. Instead, the probe was mostly built by Americans, in America.

Carrying three science instruments, the Hope mission will measure conditions in the Martian atmosphere from a unique semi-synchronous orbit high above the Red Planet. The mission is the first from the Arab world to travel to another planet.

About the size of Mini Cooper, the spacecraft was assembled at LASP’s facilities in Colorado [Laboratory for Atmospheric and Space Physics], with the help of Emirati engineers and scientists. The probe was delivered to Dubai in February for additional testing, and then was supposed to be transported to Japan in early May.

But the coronavirus pandemic forced officials to shuffle the schedule, and mission managers decided to send the probe to Japan early. [emphasis mine]

In other words, this probe might be financed by the UAE, and it might have UAE engineers and scientists involved, but essentially the UAE paid LASP to build it for them.

I am not criticizing the UAE for this effort, but to call it an Arab mission is somewhat dishonest. This is a joint American-UAE probe. If it results in producing qualified engineers in the UAE capability of building their own future planetary probe, fine. They are not doing it now, however.

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The eroding edge of Mars’ largest volcanic ash field

1:45 pm

Eroding yardangs at the edge of Mars' largest volcanic ash field
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Cool image time! In the regions between the biggest volcanoes on Mars is the Medusae Fossae Formation, a immense deposit of volcanic ash that extends across as much surface area as the nation of India. As planetary scientist Kevin Lewis of Johns Hopkins University explained to me previously,

In general, much of the [formation] seems to be in net erosion now, retaining very few craters on the surface. …One hypothesis is that this long term erosion, since it’s so enormous, is the primary source of the dust we see covering the much of the planet’s surface.

The image above, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on January 25, 2020. It shows one very small area at the very edge of the Medusae ash deposit, in a region where that deposit is clearly being eroding away by the prevailing southeast-to-northwest winds. The mesas of this ash that remain are called yardangs, their ash more tightly pressed together so that it resists erosion a bit longer than the surrounding material.

In the context map below the location of these yardangs is indicated by the white cross, right on the edge of the Medusae ash field.
» Read more

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The edge of Mars’ north polar ice cap

1:55 pm

The scarp face of the Martian north polar ice cap
Click for full image.

Cool image time! The photo to the right, cropped and reduced to post here, was taken on December 29, 2019 by the high resolution camera of Mars Reconnaissance Orbiter (MRO) and shows the many-layered scarp face of the Martian north polar ice cap. I have also rotated the image so that north is at the top. The overall height of this scarp is quite high, more than 3,500 feet.

There are a number of very cool features in this image. For example, note what at first look like puffs of clouds just below the contact between the bright and dark layers. I count almost two dozen, with the largest near the center. They are not cloud puffs, however, but areas scoured by past avalanches. According to Patricio Becerra at the University of Bern in Switzerland,

An image from a few years ago shows evidence for the same patches, so they likely happened a while back. When the avalanches or “block falls” occur, they scour the Basal Unit [the dark layer] and break up the exposed surface, causing a brighter/cloudier appearance of the ground than the undisturbed parts.

Avalanches on the scarps of the North Pole icecap occur in great numbers at the beginning of every Martian summer. As sunlight hits the scarp, it causes the carbon dioxide frost layer that settled on the cap during the winter to sublimate away as vapor, and like the freeze-melt cycle on Earth, this sublimation disturbs any unstable ice boulders on the scarp face.

During the early Martian summer, images from MRO routinely capture many such avalanches. Scientists think there could be hundreds to thousands every summer. In many ways, this is similar to the large pieces of ice that routinely calf off the foot of glaciers here on Earth, and that tourists take cruise ships to see in the inside passage of Alaska.

For context, the overview map below indicates with a gold cross where on the icecap’s edge this image is located. The red and pink areas indicate the vast dune fields that surround the icecap.
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Scientists better constrain time frame of Mars’ active dynamo

12:33 pm

Using data from the MAVEN orbiter, scientists have now constrained the time frame when Mars’ dynamo was active and producing a global magnetic field, between 3.7 and 4.5 billion years ago.

Magnetism in certain rocks on Mars’ surface indicate that the Martian dynamo was active between 4.3 and 4.2 billion years ago, but the absence of magnetism over three large basins – Hellas, Argyre, and Isidis – that formed 3.9 billion years ago has led most scientists to believe the dynamo was inactive by that time.

Mittelholz’s team analyzed new data from NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) orbiter and found clear evidence of a magnetic field coming from the Lucus Planum lava flow that formed about 3.7 billion years ago – much later than at other areas studied.

There is of course a lot of uncertainty here.

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Curiosity and other Mars orbiters threatened by budget cuts

9:25 am

The proposed budget for NASA in the Trump administrations 2021 budget request to Congress includes significant budget cuts to both Curiosity and several Mars orbiters needed to act as relay communications satellites.

The White House’s 2021 federal budget request allocates just $40 million to the mission, a decrease of 20% from the rover’s current funding. And that current funding is 13% less than Curiosity got in the previous year, said Curiosity project scientist Ashwin Vasavada, of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.

If the 2021 request is passed by Congress as-is, Curiosity’s operations would have to be scaled back considerably. Running the mission with just $40 million in 2021 would leave unused about 40% of the science team’s capability and 40% of the rover’s power output, which comes from a radioisotope thermoelectric generator (RTG), Vasavada said.

In addition, the proposed budget will require a 50% reduction in imaging by Mars Reconnaissance Orbiter, the end to the Mars Odyssey orbiter, and a significant but unspecified reduction in the use of the MAVEN orbiter.

I reported these facts back in March but there is no harm in noting them again.

The question is not whether there should be cuts at NASA. Considering the overall federal debt and annual budget deficit, NASA’s budget should be cut. The question is what to cut. The planetary program, probably NASA’s most successful program, is certainly not the program to cut. Instead, the Trump administration should be cutting the waste and badly run programs, like SLS, that spend billions and accomplish nothing.

If Congress and Trump did this, they could cut NASA’s total budget and still have plenty left over for the commercial manned program — including going to the Moon — and also increase the budget to the planetary program. I’ve been saying this since 2011, and nothing has happened in the past decade to change that conclusion.

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Perseverance’s helicopter named Ingenuity

9:15 am

After sifting through the 28,000 name suggestions submitted by K through 12 American students for naming the Mars rover Perseverance, NASA has chosen to use a suggestion from an Alabama high school student to name the rover’s prototype test helicopter Ingenuity.

As a technology demonstration, Ingenuity is a high-risk, high-reward experiment. The helicopter will ride to Mars attached to the belly of the Perseverance rover, which is preparing for launch in July or August. For several months following the rover’s landing, Ingenuity will remain encapsulated in a protective cover to shield it from debris during entry, descent and landing. When the timing in the rover mission is right, Ingenuity will be deployed to stand and operate on its own on the surface of the Red Planet. If the 4-pound (2-kilogram), solar-powered craft – a combination of specially designed components and off-the-shelf parts – survives the cold Martian nights during its pre-flight checkout, the team will proceed with testing.

If successful during its 30-Martian-day (31-Earth-day) experimental flight test window, the small craft will prove that powered flight can be achieved at Mars, enabling future Mars missions to better utilize second-generation helicopters to add an aerial dimension to their explorations.

The student, Vaneeza Rupani, had proposed the name for the rover. She instead is honored for the helicopter.

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A Martian lava flood plain

1:21 pm

A Martian lava flood plain?
Click for full image.

Cool image time! The photo to the right, cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on March 2, 2020, and shows some inexplicable shallow pits and depressions in the middle of a relatively flat and featureless plain.

Make sure you click on the image to see the full photo. Though the plain looks remarkably smooth, a handful of dark splotches are scattered about, almost all of which occur on top of small craters.

What causes these depressions? The MRO team calls this “Landforms near Cerberus Tholi.” Cereberus Tholi is a a collection of several indistinct and relatively small humps that scientists think might be shield volcanoes.

More clues come from the overall context.
» Read more

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China names its 2020 Mars mission

10:19 am

China’s official state-run press today announced that their 2020 Mars mission will be called Tianwen-1, noting that this name will be applied to all further planetary missions.

The link goes to that government state-run press, which provides no further information on Tianwen-1, such as where on Mars its lander/rover will land, its exact launch date, the instruments on board, etc. So far very very few details have been released.

What this propaganda press announcement does do is spout a lot of blather about how wonderful China is, and how we should all be thankful the communists have been in charge there. Here are some snippets to lighten your day:

  • …signifying the Chinese nation’s perseverance in pursuing truth and science
  • …a window for the Chinese public and the world to get a better understanding of China’s aerospace progress.
  • Chinese space engineers and scientists have overcome various difficulties and achieved aerospace development through self-reliance and independent innovation.
  • …promoting human welfare on the basis of equality, mutual benefit, peaceful utilization and inclusive development.

While China’s achievements in space are real (though much of the engineering was stolen or borrowed from others), these propaganda claims are junk and lies. Chinese space engineers are “self-reliant” and have “independence”? Don’t make me laugh. Everything done in their space program is dictated and controlled from the top, by the Chinese government and the Communist Party. No one is free to do anything, without their permission.

As for China’s pursuit of “truth and science”, their behavior during the Wuhan flu epidemic, originating from their country and very possibly caused deliberately or incompetently by them, makes this claim ludicrous on its face. They have lied, arrested scientists, blocked research, and distorted the scope and magnitude of the epidemic from day one.

Even a tiny bit of truth from them, from the beginning, might have prevented the panic that has overtaken the world which in turn appears to have triggered the next great economic depression, what I like to now call the Great Wuhan Depression.

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Stucco on Mars

1:13 pm

Stucco on Mars
Click for full image.

As a break from Wuhan flu madness I give you another cool image, cropped and reduced to post here, taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I call this stucco on Mars because that is exactly what it looks like. It is as someone laid down a layer of damp concrete and then ran over it roughly with a trowel to raise the knobs scattered across the surface.

The uncaptioned MRO image calls this “Aligned Mounds with Broad Summit Pits”. Those aligned mounds run across the top of the image. I suspect they are pedestal craters, left over because the impact had packed and hardened the crater so that it resisted erosion as the surrounding terrain was worn away.

The two insets, posted below at full resolutoin, focus on one of those pedestal craters as well as the distinct mesa at the bottom of the photo.
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Rock droplets hitting a Martian plain

12:42 pm

Depressions in Amazonis Planitia
Click for full image.

Cool image time! The photo the right, rotated, cropped, and reduced to post here, is not only cool, it contains a punchline. It was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on February 11, 2020 and shows one small area between two regions in the northern lowlands of Mars, dubbed Amazonia Planitia (to the south) and Arcadia Planitia (to the north) respectively.

This region is thought to have a lot of water ice just below the surface., so much in fact that Donna Viola of the University of Arizona has said, “I think you could dig anywhere to get your water ice.”

I think this image illustrates this fact nicely. Assuming the numerous depressions seen here were caused by impacts, either primary or secondary, it appears that when they hit the ground the heat of that impact was able to immediately melt a wide circular area. My guess is that an underwater ice table immediately turned to gas so that the dusty material mantling the surface then sagged, creating these wider circular depressions.

Of course, this is merely an off-the-cuff theory, and not to be taken too seriously. Other processes having nothing to do with impacts could explain what we see. For example, vents at the center of these craters might have allowed the underground ice to sublimate away, thus allowing the surface to sag.

So what’s the punchline?
» Read more

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Strange terrain in the Martian lowlands

12:42 pm

Strange terrain in northern lowlands
Click for full image.

Cool image time! The science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) yesterday released a new captioned image, entitled “Disrupted Sediments in Acidalia Planitia”, noting that the photo

…shows a pitted, blocky surface, but also more unusually, it has contorted, irregular features.

Although there are impact craters in this area, some of the features … are too irregular to be relic impact craters or river channels. One possibility is that sedimentary layers have been warped from below to create these patterns. The freezing and thawing of subsurface ice is a mechanism that could have caused this.

The image to the right, rotated, cropped, and reduced to post here, shows the lower quarter of the full image. While in some areas it does appear as if changes below the surface caused the surface to warp and collapse, as suggested by the caption, in other places it looks more like the top layers themselves sublimated away without disturbing what was below them.

Note for example the pits near the bottom of the photograph. They clearly show sedimentary layers on their cliff walls, including the tiny circular mesa in the middle of the rightmost pit.

If these pits were collapsing from below, their cliffs would be more disturbed, because it would have been those lower layers that sublimated first. Instead, it appears that the top layer disappeared first, followed by each lower layer, one by one.

This region of strange terrain is located in the middle of the northern lowland plains. The overview map below gives some context, with the small white box showing this photo’s location.
» Read more

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Rover update: Curiosity heads downhill

2:49 pm

Curiosity's last look across the Greenheugh Pedimont
Click for higher resolution.

[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.]

After finally reaching the top of the Greenheugh Pedimont (see both the March 4 and March 8, 2020 rover updates) and spending more than a month there, drilling one hole, getting samples, and taking a lot of photos, the Curiosity science team in the past week has finally sent the rover retreating back downhill, following the same route it used to climb uphill.

The panorama above was taken on April 10, 2020, and shows the last view looking south across that pedimont towards Mount Sharp, before that descent. As you can see, trying to traverse that terrain would have been very difficult, and probably very damaging to Curiosity’s wheels.
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Baby Martian volcanoes

1:28 pm

Cratered cone near Noctis Fossae
Click for full image.

Cool image time! I came across this strange feature shown on the right in my normal rummaging through the archive of the high resolution camera on Mars Reconnaissance Orbiter (MRO). The photo, rotated, cropped, and reduced to post here, focuses on what they label a “cratered cone.”

The immediate thought is that this is a volcano cone, and the craters at its peak are not impact craters but calderas. In science however such a knee-jerk conclusion is always dangerous. For example, this might instead be a pedestal crater, where the surrounding terrain was worn away over eons, leaving the crater sitting high and dry.

It is therefore important to look deeper to determine what origin of this feature might be.

First, its location, as shown in the overview map below, provides us our first clue.
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Seasonal avalanches in Martian dune gully

11:01 am

Seasonal changes in Martian dune gully
Click for full image.

The science team for the high resolution camera on Mars Reconnaissance Orbiter (MRO) today released a very cool pair of images, taken a Martian year apart, showing some significant changes that had occurred during that time in a large sand dune slope inside a crater. On the right is that pair, reduced and with the top image slightly lightened to bring out the features. As they wrote in the caption,

One large gully in particular has had major changes in every Martian winter since [MRO’s high resolution camera] began monitoring, triggered by the seasonal dry ice frost that accumulates each year.

This time there was an especially large change, depositing a huge mass of sand. The sand divided into many small toes near its end, or perhaps many individual flows descended near the same spot. Additionally, a long sinuous ridge of sand was deposited. This could be a “levee” that formed along one side of a flow, but there is not much sand past the end of the ridge, so it might also be the main body of a flow.

Nor is this dune gully the only active one in this crater, dubbed Matara Crater, located in the southern cratered highlands at about 50 degrees south latitude. If you look at the full image and compare it with an image from 2009 there are many changes across the entire slope field that extends a considerable distance to the north and south of the cropped section shown above.

At this latitude atmospheric carbon dioxide settles as frost during the winter, then sublimates away with the coming of spring. The freeze-sublimation process disturbs the sand each year, causing these avalanches.

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The icy Phlegra Mountains: Mars’ future second city

1:35 pm

Icy glaciers in the Phlegra Mountains of Mars
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About a thousand miles to the west of the candidate landing site for SpaceX’s Starship spacecraft rises a massive mountain wall dubbed the Phlegra Mountains, rising as much as 11,000 feet above the adjacent lowland northern plains.

Phlegra Montes (its official name) is of special interest because of its apparent icy nature. Here practically every photograph taken by any orbiter appears to show immense glacial flows of some kind, with some glaciers coming down canyons and hollows [#1], some filling craters [#2], some forming wide aprons [#3] at the base of mountains and even at the mountains’ highest peaks [#4], and some filling the flats [#5] beyond the mountain foothills.

And then there are the images that show almost all these types of glaciers, plus others [#6]. Today’s cool image above is an example of this. In this one photo we can see filled craters, aprons below peaks, and flows moving down canyons. It is as if a thick layer of ice has partly buried everything up the highest elevations.

None of this has gone unnoticed by scientists. For the past decade they have repeatedly published papers noting these features and their icy appearance, concluding that the Phlegra Mountains are home to ample buried ice. SpaceX even had one image taken here [#3] as a candidate landing site for Starship, though this is clearly not their primary choice at this time.

The map below gives an overview of the mountains, their relationship to the Starship landing site, and the location by number of the images listed above.
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A river canyon on Mars?

1:35 pm

Cool image time! In the most recent download of new images from the high resolution camera of Mars Reconnaissance Orbiter (MRO) were two photos, found here and here, that struck me as very intriguing. Both were titled simply as a “Terrain Sample” image, which generally means the picture was taken not because of any specific request by another scientist doing specific research but because the camera team needs to take an image to maintain the camera’s proper temperature, and in doing so they try to time it so that they can do some random exploring as well.

As it turned out, the two images were more than simply random, as they both covered different parts of the same Martian feature, what looks like a branching dry dendritic river drainage. Below is a mosaic of those two images, fit together as one image, with a wider context image to the right, taken by Mars Odyssey, showing the entire drainage plus the surrounding landscape with the white arrow added to help indicate the drainage’s location.
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Weird flat plateau on Mars

10:43 am

Weird flat plateau on Mars
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Cool image time! The image to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on December 15, 2020, and was actually a follow-up observation from an earlier image taken by the camera on Europe’s Trace Gas Orbiter (TGO), according to Dr. Livio Tornabene of the University of Western Ontario. As he explained in an email:

The team is rather polarized with their verdict on what exactly the feature is… while at first glance it appears to be a lava flow, it very well could be that these deposits eroded to yield this flow/lobate like appearance and isn’t lava at all. So as someone that is both involved with [TGO] and [MRO], I noticed that the lobate feature causing quite the debate had no coverage from [MRO].

It appears that some scientists think that instead of lava, this is a mud flow. Research presented [pdf] during the 2019 Lunar & Planetary Conference in Texas found evidence that mud could flow like lava under the right conditions.

At this point neither Tornabene nor anyone working on the TGO team have yet analyzed this new MRO image to see if they can answer this question. That this feature is located in a region just to the southeast of Marineris Valles where there is evidence both of volcanic activity and sedimentary deposition, makes answering the question even more challenging.

The data from TGO indicated [pdf] that the plateau was about 30 to 65 feet thick. Based on crater counts the age is thought to be between 1.6 to 1.9 billion years old.

What struck me about the plateau is that though it really does look like a flow, it also appears remarkably flat and smooth. Even more puzzling is that, according to the TGO paper, the plateau slopes downhill very gently (a 1% grade) to the south, not to the north as suggested by the shape of the flow. Maybe later geological events tilted the entire feature after it solidified, thus changing the grade?

Meanwhile that channel near the bottom of the image crosses through the grade and the flow, as if it was cut after the flow was placed. In other words, the flow and channel were formed separately, at different times.

Ah, the mysteries of planetary geology. If only we could just go there with a geologist’s hammer. These questions would then be so much more simple to answer.

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Changing Mars

1:12 pm

The maculae splotch dubbed Maui
For the full images click here (2019) and here (2020).

While Mars appears to be a dead planet, with no clear evidence of life so far discovered, the planet is hardly inactive. Things are changing there continuously, even if it happens at a slower pace than here on Earth.

To the right are two images, rotated, cropped, and reduced to post here, taken by the high resolution camera of Mars Reconnaissance Orbiter. The first was on January 19, 2019, shortly after the end of the global dust storm that engulfed Mars during that Martian year. The second was taken on February 14, 2020, half a Martian year later. Both show one of a string of dark splotches located on the western flanks of the giant volcano Olympus Mons. Scientists call these splotches maculae, and because of their superficial resemblance to the islands of Hawaii, have given them names matching those islands. This particular patch is dubbed Maui. Below is a map showing all the splotches and their position relative to Olympus Mons, taken from a 2019 presentation [pdf].
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Skiing dry ice boulders on Mars

2:47 pm

Dune slope, with grooves, in Russell Crater
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Cool image and video time! The image to the right, cropped and reduced to post here, shows something that when I spotted it in reviewing the newest image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO), I found it very baffling. The photo was taken on March 3, 2020, and shows an incredible number of linear groves on the slope of a large dune inside Russell Crater, located in the Martian southern highlands at about 54 degrees south latitude.

If these were created by boulders we should see them at the bottom of each groove. Instead, the grooves generally seem to peter out as if the boulder rolling down the slope had vanished. Making this even more unlikely is that the top of the slope simply does not have sufficient boulders to make all these groves.

The image was requested by Dr. Candice Hansen of the Planetary Science Institute in Tucson, Arizona, who when I emailed her in bafflement she responded like so:
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