Perseverance begins journey with 1st test drive

Perseverance's future planned route
Click for full image.

On March 4th the engineers on the Perseverance science team successfully completed the rover’s first test drive.

Ground teams commanded the rover to drive forward, turn in place, and then back up. The first 33-minute test drive covered just 21 feet, or 6.5 meters,but Perseverance will soon travel much farther. “Our first drive went incredibly well,” said Anais Zarifian, a Perseverance mobility test engineer at JPL.

Perseverance has six aluminum wheels, each with titanium spokes for support, and a suspension capable of traveling over rocks as big as the wheels themselves. The one-ton rover is based on the design of NASA’s Curiosity rover, which landed on Mars in 2012, but with some improvements.

The wheels on Perseverance are sightly narrower, have a larger diameter, and are made of thicker materials, Zarifian said. Engineers also changed the tread pattern on the wheels to reduce the risk of damage from sharp rocks, which created dings and cuts in Curiosity’s wheels.

The map above shows the route the science team has presently chosen for Perseverance, a revision from earlier routes created prior to landing. The white dot on the right is the rover’s present position, the blue and purple lines are two alternative routes they are considering for their route to the delta coming out of Neretva Vallis. The yellow route up the delta is especially exciting in that it gets them onto it much sooner than previous plans.

Which route they choose for the initial journey I think will partly depend on which provides the best location to test fly Ingenuity, the experimental helicopter on the rover. Scientists and engineers I am sure are presently pouring over high resolution images from Mars Reconnaissance Orbiter (MRO) in order to make that choice. At this link, centered on Perseverance’s present location, you can take a look at all those images by MRO by selecting the arrow icon at the top and then clicking on any red box. Because so many photos have been taken there is a lot of overlap, so each click will give you many pictures to look at.

Ice-filled Martian sinkhole

Ice-filled pit on Mars
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Cool image time! The pit shown in the high resolution photo to the right (image rotated, cropped, and reduced to post here) was taken on January 25, 2021 and labeled by the Mars Reconnaissance Orbiter (MRO) “Collapse Pit in Graben with Ice Fill.”

There is a lot of information in that title. First, a graben is a geological feature where a section of terrain drops relative to the surrounding terrain, producing a depression. Second, it appears the graben in this region is mostly filled with debris, probably wind-blown dust or sand or volcanic ash.

Third, at this particular spot the filling material sank, like a sinkhole on Earth, creating the pit.

And fourth, and maybe most intriguing, the scientists think that this pit is now filled with ice. At 47 degrees north latitude, the location is prime for such ice, and the interior material resembles similar glacial features seen in many other mid-latitude craters.
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Dao Vallis: A giant river of ice on Mars

The glacier in Dao Vallis
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on December 26, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows an apparent glacial flow in a canyon heading downhill to the southwest, with evidence of a gully on its western wall whose collapse apparently squeezed into that glacial flow, pushing it to the east.

What makes this particular image interesting is not its uniqueness but just the opposite. Almost every high resolution picture along the length of this 750 mile long canyon, dubbed Dao Vallis, shows the same thing, an ice-filled ravine with that ice flowing like a river downhill.

The overview map below provides some spectacular context.
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China releases first Tianwen-1 images of rover landing site

The rover landing site for Tianwen-1's rover

The new colonial movement: China yesterday released the first two images taken by its Mars orbiter Tianwen-1 of its planned rover landing site in the northern lowland plains of Mars.

The image to the right is a mosaic of two wide angle photos from the context camera on Mars Reconnaissance Orbiter (MRO). The white cross is the spot of the latitude and longitude that had previously been leaked to the Chinese press as the landing site. The white box shows the area covered by the only high resolution MRO photo, as of October 2020. Since then MRO has taken a number of additional high resolution images of this area.

The red boxes mark the areas covered by Tianwen-1’s two new images. Below is a reduced version of the larger of these two photos.
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Mining country on Mars?

The southern end of Nili Fossae

Today’s cool image might very well be giving us a glimpse of one of the most promising regions on Mars for future mining. The photo to the right, rotated, cropped, and reduced, is made up of two context camera images from Mars Reconnaissance Orbiter (MRO), found here and here. I chose to begin with this wider context camera mosaic because this is one of the rare times the context camera is more exciting an image than the close-up high resolution photo.

This photo covers the southern end of the one of the two curved fissures dubbed Nili Fossae and are thought to be left over evidence of the giant impact that created Isidis Basin to the southeast. These two fissures are about 300 miles long, and can be as much as 1,600 feet deep in places. At this southern end, we can see what look like at least two different drainage channels feeding into the fissure.

The overview map below provides the context of this location on Mars, including its relationship to Jezero Crater where Perseverance now sits.
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Cave boxwork on the Martian surface

Boxwork in Wind Cave on Earth
Boxwork inside Wind Cave, South Dakota, mere inches across.

Anyone who has ever visited either Wind or Jewel caves in South Dakota has likely seen some wonderful examples of the cave formation boxwork, formed when the material in cracks is more resistant to erosion that the surrounding bedrock, which once eroded away leaves behind the criss-crossing ridges seen in the picture to the right.

Today’s cool image provides us what appears to be an example of boxwork on Mars. However, unlike on Earth it is not in a cave but on the surface. It is also much larger. Instead of the ridges being almost paper thin and stretching for inches or feet, this Martian boxwork is feet wide with ridges extending hundreds of feet in size, as shown by today’s cool image below.
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A deep south Martian dune with bright patches

Dune with bright patches
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Cool image time! Last week the MRO science team posted a new captioned image entitled “Bright and Dark Dunes” featuring a particularly large single dune in the floor of a 25-mile-wide unnamed crater located at about 68 degrees south latitude. The photo to the right, rotated, cropped, reduced, and color enhanced to post here, shows that dune. According to the caption, written by Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona,

This image shows a large sand dune with bright patches. Martian dunes near the poles often have bright patches in the spring, when seasonal frost is lingering. However, this image is from late summer, when frost is long gone. What is going on here?

A close-up look with [MRO’s high resolution camera] provides some clues. The bright patches are made up of large ridges that look like wind-blown bedforms. Additionally, the bright patches are yellowish in the infrared-red-blue image. In enhanced color, most sand on Mars is blue but dust is yellow. This suggests that the bright bedforms are either built from, or covered by, dust or material with a different composition.

Thus, the bright patches reveal either aspect of the dune’s underlying structure, either inherent in the bedrock itself, or the texture of its surface that allows it to hold more dust. As Dundas adds, “I think more study would be needed to determine the answer in this particular case.”

There are other aspects of this dune that can be seen by a look at the wider view afforded by MRO’s context camera below.
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Skiing dry ice boulders on Mars, captured in action!

Grooves in dune created by sliding dry ice blocks
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Today’s cool image is an update on a previous cool image published in April 2020 about how scientists believe the grooves seen on the slope of a giant dune in Russell Crater on Mars are believed to be formed by frozen blocks of carbon dioxide sliding down the slope when spring arrives. The photo to the right, taken on March 3, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and rotated and cropped to post here, shows these grooves. As I wrote then,

Because the block is sublimating away, the gas acts as a lubricant so that it can slide down the hill. If large enough, the dry ice block will stop at the base of the hill to disappear in a small pit. If small enough, it actually might completely vaporize as it slides, explaining the grooves that appear to gradually fade away.

The scientists actually did a test on Earth, buying a dry ice block at a grocery store and releasing it at the top of a desert dune. Go to my April 2020 link above to see the very cool video.

Several planetary scientists did further combing through many MRO photos of this dune and now think they have spotted examples where the camera actually captured a block as it was sliding downhill.
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Searching for ice in the Martian low latitudes

Low latitude crater with intriguing debris on its floor
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Today’s cool image well illustrates the effort of planetary scientists to map out the range of buried ice on the Martian surface. Taken on December 13, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and rotated, cropped, and reduced to post here, it shows a 3.5-mile-wide crater located in the southern cratered highlands, but for those cratered highlands at the very high northern latitude of 24 degrees.

The black streaks on the crater’s interior slopes are probably slope streaks, but these are not the subject of this article. Instead, it is the material that covers the crater’s floor. These features resemble the glacial fill material that scientists have found widespread in the latitude bands between 30 to 60 degrees latitude. However, this crater is farther south, where such ice would not be stable and should have sublimated away.

Could there still be ice here? I emailed the scientist who requested the photo, Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona, and asked him what I was looking at. His answer:
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Land of rovers

Overview map

Today’s cool image is in honor the two newest Martian rovers, Perseverance (which now sits quite comfortably in Jezero Crater, ready to begin what will probably be more than a decade of exploration on the Martian surface) and China’s yet-to-be-named rover (set to hopefully soft land on Mars some time in late April).

The overview map to the right shows us the region where both rovers shall wander. The black box in Jezero Crater is where Perseverance now sits. The red cross about 1,400 miles away is the believed landing zone for China’s rover, located in Utopia Planitia at about 25 degrees north latitude. The Viking 2 landing site is just off the edge of the northeast corner of the map.

The latitude of 30 degrees, as indicated by the white line, is presently an important dividing line based on our present knowledge of Mars. South of that line the terrain is generally dry, though there is evidence that water in some form (liquid or ice) was once present. North of that line scientists have found evidence of considerable ice below the surface, with its presence becoming increasingly obvious the farther north you go.

Today’s cool image, shown below, is north of that line at 33 degrees latitude in Utopia Planitia, and is marked by the white cross, about 500 miles to the northwest of the Chinese rover’s landing site.
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Martian pits or dark splotches?

Martian pits or dark splotches?
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Cool image time! The photo to the right, cropped to post here, was taken on January 2, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a windswept sandy region of ridges and dunes with two dark features nestled between ridges.

What are these dark patches? At the available resolution they appear to be deep pits, with the one on the right having a significant overhang. And if these are pits, they would appear significantly different than most of the previously identified Martian pits, which are usually somewhat circular in shape. These features have very complex shapes, as if the pit is conforming itself to the terrain that surrounds it.

The resolution, however, is not good enough to confirm this interpretation. These dark patches could also be exposed volcanic material, darker than the surrounding terrain. The location, as shown in the overview map below, adds weight to this interpretation.
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First panorama from Perseverance

The Perseverance science team has released the first panorama taken by the Perseverance rover after landing on Mars February 18th.

Below the fold however I have embedded something far better than the science team’s mosaic. Andrew Bodrev has taken these same navigation camera images and created a 360 degree virtual reality panorama, one that you can pan and tilt at your own pleasure. The view also includes the sounds of the Martian winds from the rover’s microphone. If you pause it you won’t hear the sounds, but you can scan and rotate for as long as you want.

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Partly ice-filled Martian crater?

Partly ice-filled Martian crater?
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Time for another cool Martian image. The photo to the right, rotated, cropped, and reduced to post here, was taken on January 3, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The section I have focused on is a single crater about a mile and a half wide.

What makes this crater interesting is the material that appears piled up against the crater’s northern half. Furthermore, both the floor of the crater as well as this piled up material looks like it is eroding away, kind of like a block of ice which is having warm water sprayed on it.

So, is this glacial ice?
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Eroded mound in Mars’ glacier country

Eroded mound in Mars' glacier country
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Cool image time! The image to the right, reduced to post here, was a captioned release today by the science team of the high resolution camera on Mars Reconnaissance Orbiter (MRO). It is located in Deuteronilus Mensae, a region of chaos terrain in the transition zone between the northern lowland plains and the southern cratered highlands that is also part of a 2,000 mile-long band that I call Mars’ glacier country. From the caption, written by Dan Berman, senior scientist at the Planetary Science Institute in Arizona:

Lobate debris aprons are commonly found surrounding dissected plateaus in the Deuteronilus Mensae region of Mars. They have been interpreted as debris-covered glaciers and radar data have shown their interiors to be composed of pure ice.

The mound in this image is slightly removed from most of the other plateaus, and the [debris apron] surrounding it is highly degraded. The sharp scarps on the western and eastern sides of the mound indicate that a great deal of the ice once found in these landforms has since sublimated away, leaving behind these collapsed debris cliffs.

I wonder if further research might find an ice layer in those cliff walls, especially because this photo strongly suggests that much of this mound is made of ice that is sublimating away or has flowed downward to form the debris aprons as well as that central gully.

The overview map below shows its location in Deuteronilus Mensae as well as showing almost all of the entire band of Mars’ glacier country.
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Enigmatic channel on Mars

Enigmatic channel on Mars
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Cool image time. The photo to the right, rotated, cropped, and reduced to post here, was taken on October 26, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and labeled by the science team as simply an “Enigmatic Channel in Syrtis Major.”

It shows a channel going downhill to the northeast east in a series of steps, separated cliffs that in the southwest hikers call pour-offs, with the channel becoming initially deeper and then slowly becoming more shallow, until the next pour-off. On Earth the pour-offs would be waterfalls, with a deep pond at the base. On Mars?

Without doubt this channel poses mysteries, but maybe with a little research we can make it less enigmatic. Asl always, the overview map below gives context, and helps give a possible explanation for what created this channel.
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Strange corroding features on Mars

Strange corroding features on Mars
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Cool image time! The photo to the right, rotated, cropped, and enhanced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 4, 2020. It shows what appears to be features that are either corroding or eroding away, with the lower areas filled with rippling sand dunes.

The circular features might be ancient craters. The material that partly fills them might be a layer of dust or sand that the wind is slowly blowing away to dig out the depressions along the southern cliff wall.

According to the MRO science team’s interpretation of the colors produced by the high resolution camera [pdf], the dark blue colors here are likely “coarser-grained materials (sand and rocks)”, while the orange-red material on the higher terrain is likely dust.

Could this material be evidence of buried ice eroding away? At first I thought so, and then I took a look at the photo’s location, as shown in the overview image below.
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New paper: Underlying ice layer seen in Martian gullies at LOW mid-latitudes

Snow on Mars?
Click to see full image.

In a paper just published, scientists are proposing that bright areas seen in the low mid-latitude gullies on Mars are the underground ice table newly exposed as surface dust is removed.

This paper is a reiteration in more detail of a previous presentation [pdf] by these same scientists at the 2019 the 50th Lunar and Planetary Science Conference in Texas and reported here in March 2019.

The image to the right, from the paper, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) in 2009, and has been cropped to post here. The white streaks are what the scientists propose is that exposed underground ice table. At 32.9 south latitude, this particular gully would be the closest to the equator that such an ice layer has been identified. All the previous ice layer discoveries have been in the ice scarps found at latitudes above 50 degrees. As the paper’s lead author, Aditya Khuller at Arizona State University, explained in to me in an email, “We believe we are seeing exposures of dusty ice that likely originated as dusty snow.” From their paper:

We suggest … that the light-toned materials are exposed H2O ice. … [T]he appearance, and then subsequent disappearance of these light-toned materials, suggests that they are some form of volatile, such as dusty ice, rather than dust alone. … [The appearance] of these light-toned materials is similar to the >100m thick, light-toned ice deposits exposed on steep mid-latitude scarps, indicating that these materials are probably also ice, with some amount of dust on, and within the ice.

The layer would have likely been laid down as snow during a time period (a long time ago) when the rotational tilt of Mars, its obliquity, was much higher than today’s 25 degrees. At that time the mid-latitudes were colder than the poles, and water was sublimating from the polar ice caps to fall as snow in the mid-latitudes.

The overview map below reveals some additional intriguing possibilities.
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Rover update: The rovers are coming! The rovers are coming!

With the imminent landing on Mars of both the American rover Perseverance only days away on February 18th followed by China’s rover in April, I think it time for a new rover update, not only providing my readers a review of the new landing sites but a look at the most recent travels of Curiosity on Mars and Yutu-2 on the Moon.


Curiosity's view of the base of Mount Sharp, February 12, 2021
Click for full resolution image.

Overview map of Curiosity's most recent and future travels

The panorama above, made from four images taken by Curiosity’s right navigation camera on February 12, 2021 (found here, here, here, and here), looks south to the base of Mount Sharp, now only a short distance away. The yellow lines on the overview map to the right show the area this panorama covers. The white line indicates Curiosity’s previous travels. The dotted red line in both images shows Curiosity’s planned route.

The two white dots on the overview map are the locations of the two recurring slope lineae along Curiosity’s route, with the plan to get reasonable close to the first and spend some time there studying it. These lineae are one of Mars’ most intriguing phenomenon, seasonal dark streaks that appear on slopes in the spring and fade by the fall. There are several theories attempting to explain their formation, most proposing the seepage of a brine from below ground, but none has been accepted yet with any enthusiasm.
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Inexplicable ridges in Hellas Basin on Mars

Sinuous ridge in Hellas Basin
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Time for some more cool but mysterious Martian images! The photo to the right, rotated, cropped, and reduced to post here, is the first of two images today, both of which show the ridges but of a completely different nature. Both are located in Hellas Basin in Mars southern hemisphere.

This first picture was taken on September 4, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows a sinuous complex that resembles to a remarkable extent a set of river tributaries, but is instead a set of raised ridges rather than a canyon system.

Scientists have found more than 10,000 miles of such ridges in the northern hemisphere in Arabia Terra, the most extensive transition zone between the southern highlands and the northern lowlands, and have dubbed them fossilized rivers. From a 2016 press release:

The inverted channels are similar to those found elsewhere on Mars and Earth. They are made of sand and gravel deposited by a river and when the river becomes dry, the channels are left upstanding as the surrounding material erodes. On Earth, inverted channels often occur in dry, desert environments like Oman, Egypt, or Utah, where erosion rates are low – in most other environments, the channels are worn away before they can become inverted. “The networks of inverted channels in Arabia Terra are about 30m high and up to 1–2km wide, so we think they are probably the remains of giant rivers that flowed billions of years ago. Arabia Terra was essentially one massive flood plain bordering the highlands and lowlands of Mars. We think the rivers were active 3.9–3.7 billion years ago, but gradually dried up before being rapidly buried and protected for billions of years, potentially preserving any ancient biological material that might have been present,” added Joel Davis.

Nor are such features on Mars limited to Hellas and Arabia Terra. For a particularly spectacular feature in the cratered highlands see this 2019 post.

The origin of these sinuous ridges in Hellas might have a similar origin as these other fossilized rivers. At present the bottom of Hellas, the deepest basin on Mars, is a place with little signs of ice. In the past there is evidence that lakes once existed here, so we cannot rule out water as a cause.

At the same time, Hellas was formed by a gigantic impact. One cannot dismiss the possibility of a volcanic origin, impact melt left over from the heat of that crash.

Today’s second ridge complex in Hellas looks far different.
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Another “What the heck?!” image on Mars

Click for full image.

Today’s cool image, taken on September 2, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and cropped and reduced to post here, is one that I will make very little attempt to explain. It falls into a category I call “What the heck?!” The uncaptioned website labels this “Ringed Ridges in Kasei Valles”, which merely describes what we see.

This isn’t an impact crater. The rings don’t fit any morphology I’ve ever seen for such features.

Could we be looking at some type of glacial feature? The latitude, 29 degrees north, makes this unlikely but possible. Even so, it sure doesn’t look like it. The ripples in the center and between the ridges are sand dunes, not glacial features.

Might this be a volcanic vent, with the concentric ridges marking multiple eruptions? Maybe, but if so I’ve never seen any volcanic vent or caldera that looked quite like this.

The overview map below gives some context, but hardly explains anything.
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OSIRIS-REx has begun its return to Bennu

On January 14th the OSIRIS-REx team fired the spacecraft’s engines to halt its drift away from the asteroid Bennu and begin its return for one last reconnaissance before heading to Earth with its samples.

OSIRIS-REx executed the first maneuver on Jan. 14, which acted as a braking burn and put the spacecraft on a trajectory to rendezvous with the asteroid one last time. Since October’s sample collection event, the spacecraft has been slowly drifting away from the asteroid, and ended up approximately 1,635 miles (2,200 km) from Bennu. After the braking burn, the spacecraft is now slowly approaching the asteroid and will perform a second approach maneuver on Mar. 6, when it is approximately 155 miles (250 km) from Bennu. OSIRIS-REx will then execute three subsequent maneuvers, which are required to place the spacecraft on a precise trajectory for the final flyby on Apr. 7.

OSIRIS-REx is scheduled to depart Bennu on May 10 and begin its two-year journey back to Earth. The spacecraft will deliver the samples of Bennu to the Utah Test and Training Range on Sep. 24, 2023.

While they will gather images of the whole asteroid, their number one goal will be to get high resolution photos of the sample-grab site Nightingale to see how it was changed by that sample grab. The spacecraft pushed into the asteroid’s rubble pile about 1.6 feet, and that act certainly disturbed both the interior and surface. By comparing the before and after pictures scientists can garner a lot of information about the asteroid’s make-up, density, and structure. It will also teach future engineers what to expect when next they try to touch another rubble-pile asteroid.

The Icy Surface of Mars

The extent of ice on Mars

Two newly published science papers in the past few days have once again reinforced the growing evidence that much of Mars from 30 degrees latitude to its poles is very icy, with much of that ice found close to the surface.

The map above, adapted and annotated by me from figures 4 and 12 of one of those papers (“Widespread Exposures of Extensive Clean Shallow Ice in the Mid‐Latitudes of Mars”), show the areas on Mars where the evidence suggests ample and easily accessible ice, underground but close to the surface.

The red dots and diamonds indicate recent impact craters that temporarily exposed the underground ice layer that would normally not be visible. The white dots and diamonds indicate ice scarps with visible ice layers in their cliff faces. The size of these locations is greatly exaggerated.

The two hatched lines at 30 degrees latitude, north and south, indicate the closest to the equator that scientists have detected evidence of glacial ice. It is also the closest to the equator that the second new paper, “Water Ice Resources Identified in Martian Northern Hemisphere “, has found evidence of underground ice in the north. From the abstract of this second paper:
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New theory to explain the Martian seasonal streaks

The uncertainty of science: Scientists have proposed a new explanation for explaining the Martian seasonal streaks called recurring slope lineae that appear each spring and then fade over time.

Lineae, while unique to Mars, are different than the other similar Martian feature called slope streaks, which are not seasonal and have a somewhat different appearance and morphology.

This new proposal refines some of the past ideas for the seasonal cause of lineae.

Previous ideas suggested that liquid debris flows or dry granular flows caused this movement. Neither model can completely account for the seasonal martian flow features known as Recurring Slope Lineae (RSL). The team alternatively hypothesizes that small-scale ice melting in the near-surface regolith is causing changes at the surface that make it vulnerable to dust storms and wind. As a result, the RSL features appear and/or expand on the surface of Mars today. Further, the team believes that the thin layers of melting ice result from interactions between underground water ice, chlorine salts, and sulfates, which create an unstable, liquid-like flowing slush instigating sinkholes, ground collapse, surface flows, and upheave.

…Previous studies have suggested RSL are related to chlorine salts and noted their occurrence in regions of high sulfate outcrops. The current study extends these observations with a near-surface cryosalt activity model based on field observations and lab experiments. However, the exact mechanism of RSL formation on Mars still remains a mystery. [emphasis mine]

The mainstream press will make a big deal about this, but it really does nothing but add some nuance to previous theories. We really still do not know what causes lineae, as the highlighted text above notes.

More weird features and changes on Mars

Some strange stuff on Mars
Click for full 2020 photo.

Overview map

Cool image time! The photo to the right, rotated, cropped, reduced, and annotated to post here, was taken on September 28, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Uncaptioned and labeled “Reticulate Bedform Change Detection on Arsia Mons West Flank,” it shows a whole bunch of strange features in addition to a change that occurred sometime in the past two years.

I think it also well illustrates in one image how alien Mars is.

The main features in this photo are what scientists have dubbed reticulate bedforms. These features, found mostly in the high elevations on the flanks of the giant volcanoes in the Tharsis Bulge to the west of Valles Marineris, are thought to be ancient dunes made of volcanic dust and debris that has solidified into an aggregate. These dunes are found with a variety of patterns.

Aggregates on the flanks are transported downslope by katabatic winds and form linear and “accordion” morphologies. Materials within the calderas and other depressions remain trapped and are subjected to multidirectional winds, forming an interlinked “honeycomb” texture. In many places on and near the volcanoes, light-toned, low thermal inertia yardangs and indurated surfaces are present.

The photo to the right appears to show all three patterns, even though it is located on the northwestern slopes of of Arsia Mons, the southernmost of the string of three giant volcanoes in the Tharsis Bulge. On the overview map to the right, this photo’s location is indicated by the white box. The black boxes indicate the location of all the pits caves that surround Arsia Mons which I have previously posted about on Behind the Black.

It is intriguing that, at least at this point, these particular reticulate bedforms on the slopes of Arsia Mons happen to be in a region where few cave pits have so far been identified. It could be that the conditions that form each are mutually exclusive. If you get pits on the slopes of Martian volcano you can’t have reticulate bedforms. Or maybe not all the pits have yet been located, or the flanks of the volcano has many more reticulate bedforms that I simply have not documented.

Either way, this particular cool image has two areas of interest, as noted by the white boxes above.
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On the edge of Mars’ giant volcanic flood plain

Flows and pitted material on the edge of Mars' great volcanic flood plain
Click for full image.

Cool image time! The photo to the right, cropped and reduced to post here, was taken on September 30, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Uncaptioned, it shows what the science team labels “Flows and pitted material in Terra Sirenum.”

Downhill is to the southeast, which means the pitted material forms some sort of filled terrain, with the surface eroded similarly everywhere. At a latitude of 32 degrees south, these flows could conceivably be glacial features. Are they?

A wider look might help answer that question. Below is a photo taken by MRO’s context camera, cropped and reduced to post here.
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The freaky floor of Mars’ Hellas Basin

The perplexing floor of Hellas Basin
Click for full image.

Today’s cool image takes us to the Death Valley of Mars, Hellas Basin, a place I like to call the basement of Mars. The photo to the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on September 28, 2020, and gives us another example of the very strange and inexplicable geological formations that are often found on the floor of Hellas.

The picture was taken not as part of any particular research project, but somewhat randomly for engineering reasons. In order to maintain the proper temperature of MRO’s high resolution camera, it must take images in a regular cadence. When large gaps in time occur between requested images, the camera team then picks locations to fill those gaps, sometimes randomly, sometimes based on a quick review of earlier wide angle images.

Sometimes these “terrain sample” images are quite uninteresting. More often they hold baffling surprises.

I think the photo to the right falls into the latter category. Though the terrain covered by the full image is largely flat and lacking in large features, the surface is strewn with perplexing small details.

The light streaks might be dust devil tracks, but why are they light here when such tracks are routinely dark everywhere else on Mars? What formed the many parallel small ridges? What caused the smooth solid patch near the photo’s center top? And why do the ridgelines at the western edge of that patch run in almost a perpendicular direction to the other ridges?

All a mystery, but then the floor of Hellas Basin is filled with such mysteries. Below is a list of some other cool images of the floor of Hellas, all weird and mystifying. Also below is an overview elevation map of Hellas Basin, with darker blue indicating the lowest elevations. The white cross marks the location of today’s photo.
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Antarctica data adds weight to hypothesis that glaciers shaped Mars

New data from an Antarctica ice core strengthens the hypothesis that the flow of glaciers, not liquid water, helped shape the meandering canyons on Mars.

The data was the discovery of the mineral jarosite deep within the south pole ice-cap. Jarosite needs water to form. Previously it was generally believed it formed in conjunction with liquid flowing water. On Mars, which appears to have lots of jarosite, scientists have struggled for decades to figure out how enough liquid water could have existed on the surface of Mars to produce it.

The discovery of jarosite deep inside the Antarctic ice cap now suggests that it can form buried in ice, not liquid water. According to the scientists,

the jarosite was born within massive ice deposits that might have blanketed [Mars] billions of years ago. As ice sheets grew over time, dust would have accumulated within the ice—and may have been transformed into jarosite within slushy pockets between ice crystals.

From the paper’s conclusions:

The occurrence of jarosite in TALDICE [in Antarctica] supports the ice-weathering model for the formation of Martian jarosite within large ice-dust deposits. The environment inside the Talos Dome ice [in Antarctica] is isolated from the Earth atmosphere and its conditions, including pressure, temperature, pH and chemistry, provides a suitable analogue for similar Martian settings. Dust deposited at Talos Dome is also similar to Martian atmospheric dust, being both mostly basaltic. Within thick ice deposits it is likely that the environment would be similar at Talos Dome and under Mars-like conditions since both settings would contain at cryogenic temperatures basaltic dust and volcanogenic and biogenic (for Antarctic only) sulfur-rich aerosols. … Considering this context, it is reasonable that the formation of jarosite on Mars involves the interaction between brines and mineral dust in deep ice, as observed in TALDICE. This mechanism for Martian jarosite precipitation is paradigm changing and strongly challenges assumptions that the mineral formed in playa settings.

Playa settings are places where there is standing liquid water, slowing drying away.

This result is another piece of evidence that ice and glaciers were the cause of the Martian terrain that to Earth eyes for decades was thought to have formed by flowing water. It also continues what appears to be a major shift on-going in the planetary science community, from the idea of liquid water on Mars to that of a planet dominated by glacial and ice processes.

Back to Mars’ glacier country

Tongue-shaped glacial flow on Mars
Click for full image.

The cool image to the right, rotated, cropped, and reduced to post here, was taken on November 3, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labels a “Possible Tongue-Shaped Flow Feature in Protonilus Mensae.” There is no caption, so I will try to provide.

Protonilus Mensae is part of the long string of chaos terrain that runs about 2,000 miles along the transition zone between the southern cratered highlands and the northern lowland plains at about 30 to 40 degrees north latitude, and includes the other mensae regions dubbed Deuteronilus to the west and Nilosyrtis to the east. This region of Mars I like to call glacier country, because almost every high resolution photograph appears to show glacial features. To get an idea what I mean, take a gander at these past posts, their locations indicated by number in the overview map of Protonilus Mensae below:
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The strange moated mesas of the Kasai Valley on Mars

Overview map

In showing my readers today’s cool image, I want to present it as it is seen by scientists, first from a far distance that with time increasingly zooms in to reveal mysteries on a very human scale.

The overview map to the right essentially gives us the view of Mars as seen by scientists following the Mariner 9 orbiter mission that began mapping the Martian surface in late 1971 after the conclusion of a global dust storm that had hidden its surface initially. As the first high resolution map of Mars, the orbiter revealed numerous puzzling and surprising features, including the largest volcanoes and canyons in the solar system. The orbiter also found that the red planet’s surface was comprised of two very different regions, the northern lowland plains and the southern cratered highlands.

The overview map, covering from about 13 degrees south latitude to about 34 degrees north latitude, shows us all but the southern cratered highlands. The white box in Kasai Valles is where today’s cool image is located. Both Kasai and Valles Marineris represent those giant canyons, all invoking to Earth eyes the possibility of catastrophic floods of liquid water sometime in the past.

Ascraeus Mons is the northernmost of the three giant volcanoes east of the biggest volcano of all, Olympus Mons. All sit on what scientists now call the Tharsis Bulge.

Chryse Planitia, where Viking-1 landed in 1976, is part of those northern lowlands that some scientists believe might have been once had an intermittent ocean sometime in the past. Today’s image is about 600 miles from the outlet into Chryse Planitia.

The geological mystery of all these features demands a closer look, something that scientists have been pursuing now for more than a half century.
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The pit caves of Mars: Can humans someday live in them?

Four more pits in the Tharsis Bulge on Mars

It has been more than four months since my last report on the pits of Mars. Time to do another.

The collage to the right shows the four different pits photographed by the high resolution camera of Mars Reconnaissance Orbiter (MRO) since October. The links to each image are:

Like almost all the cave pits so far found on Mars, all are in the Tharsis Bulge of giant volcanoes to west of Valles Marineris. The overview map below shows these pits in the context of every other pit in this region that I have featured on Behind the Black.
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