geology – Page 84 – Behind The Black

Slope streaks in frozen lava flows on Mars

December 29, 2021 12:30 pm Robert Zimmerman

Click for full image.

Cool image time! The photo to the right, cropped and reduced to post here, was taken on June 5, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a ridgeline at the base of the giant volcano Pavonis Mons, with slope streaks on ridge’s north and south sides.

Slope streaks are a mysterious phenomenon unique to Mars. While they resemble an avalanche, they do not change the topography of the surface at all. They appear to occur randomly year round, fading slowly with time. Also, while most are dark, scientists have also spotted bright slope streaks as well.

Slope streaks also only appear on surfaces covered with a layer of fine dust, something that is obviously the case in the cool image to the right. There is so much dust on the surface here that bedrock only appears at the top of the ridge, peeking out in only a few places.

The location of this image, as shown in the overview map below, adds some additional details.
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The barren rocky terrain in the mountains of Gale Crater

December 22, 2021 9:52 am Robert Zimmerman

Click for full resolution image. Original photos can be found here, here, here, here, and here.

Click for interactive map.

Cool image time! Curiosity yesterday used its navigation cameras to take a panorama of the view inside Maria Gordon Notch. The mosaic above, created from five images taken by the right navigation camera, shows the view looking south and uphill towards Mount Sharp. The heights of the nearest four hills are likely ranging from 30 to 100 feet.

The red dotted line indicates the planned route out of Gordon Notch and up onto the Greenheugh Pediment. If you click on the panorama to look at the full resolution version, you will see that the exit route looks extemely rough, possibly too rough for Curiosity to handle. How the science team handles this issue will be fascinating to watch in the coming weeks.

The map to the right gives us an overview. The white line is Curiosity’s actual travels. The red dotted line marks the planned route. The yellow lines indicate the area covered by the panorama above.

The most striking feature of this Martian terrain is its stark barrenness. All one can see in all directions are rocks and inanimate geology. There is no life, none at all. On Earth it is practically impossible to find any mountainous spot as barren as this, even in the most extreme and hostile environments.

As I’ve said before, Mars is strange, Mars is wonderful, and above all, Mars is alien.

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Curiosity: Through the notch and looking back

December 20, 2021 11:46 am Robert Zimmerman

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The Mars rover Curiosity has now climbed up into Maria Gordon Notch. The image to the right, reduced to post here, was taken by the rover’s left navigation camera and looks back at the entrance to the notch, with the floor and rim of Gale Crater beyond. The crater floor is about 1,700 feet below and the rim is about 30 miles away.

The red dotted line indicates the path Curiosity took after entering the notch, traveling about 80 feet to the southeast. The rover will continue south inside the notch for another 800 feet or so and then turn west, climbing out of the notch and up onto the Greenheugh Pediment and continuing west until it gets to the base of Gediz Vallis Ridge, a ridge that had been in prominent view about a year ago when the rover was north of it but lower down the mountain. (See the panorama in this February 2021 post.)

Below is another picture from a day earlier, this time taken by the rover’s high resolution mast camera. I think it looks up at the top of the western cliff, but now looks at that cliff after having gone past it slightly.
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Perseverance scientists: First volcanics then water in Jezero Crater

December 17, 2021 9:45 am Robert Zimmerman

On December 15th the Perseverance science team presented a summary of the rover’s first nine months exploring the floor of Jezero Crater, finding evidence first of volcanic lava activity followed by several periods where water covered the these same rocks.

“These rocks that we originally thought might be sedimentary rocks, these are in fact igneous [volcanic] rocks,” said Kelsey Moore at the California Institute of Technology (Caltech). “And even more excitingly, they’re not just igneous rocks – there’s more history to the story.”

The analysis of the rocks’ compositions revealed minerals that are generally produced by interactions between water and rock, as well as traces of two different salts that were probably left behind as salty water flowed through the cracks and pores in the volcanic rock.

The variety of minerals indicates that these rocks were probably underwater at least twice. “Two different types of liquid with two different types of chemistries points towards two different episodes of liquid water interaction,” said Eva Scheller, also at Caltech.

It seems strange that the scientists were surprised that Jezero Crater has a history of volcanic activity. Most craters when formed have what is called impact melt in their crater interior. The impact not only carves out the crater, the heat of impact melts the rock. Possibly the scientists expected such impact melt to be well buried and not accessible to Perseverance.

Regardless, this data will be used as the baseline for documenting the geological history of this region on Mars as Perseverance continues its journey across the floor of the crater, up onto the delta, and then out of the crater into the uplands beyond.

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Cracking glaciers on Mars

December 16, 2021 11:47 am Robert Zimmerman

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Cool image time! The photo to the right, cropped and reduced to post here, was released today as the picture of the day for the high resolution camera on Mars Reconnaissance Orbiter (MRO). Located in the 2,000 long northern mid-latitude strip that I dub Mars’ glacier country, it shows many of the numerous glacial features that are routinely found in images taken in this region. According to Dan Berman, senior scientist at the Planetary Science Institute in Arizona, who wrote the caption,

This observation shows a lobe-shaped debris apron emanating from a massif (shown in the upper left of the image) in the Protonilus Mensae region in the Northern Hemisphere of Mars. These aprons are composed of nearly pure water ice with a layer of debris on the surface protecting the ice from sublimation (going directly from a solid to gaseous state). This image shows different terrain types on the apron that indicate the presence and flow of ice, from smoother polygonal terrain closer to the massif, to rougher, patterned ground commonly called “brain terrain.” Also visible on the apron are a series of linear pits.

Protonilus Mensae is the central mensae region in that mid-latitude strip of glaciers.The overview map below shows the location of this photo in that region. Also below is a close-up of the linear pits and cracked terrain surrounding that oblong mound, as indicated by the white rectangle.
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Scientists discover underground reservoir of hydrogen, likely ice, near Martian equator

December 16, 2021 8:58 am Robert Zimmerman

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In what could be a very significant discovery, scientists using Europe’s Trace Gas Orbiter (TGO) have discovered a surprisingly large underground reservoir of hydrogen, likely ice, near Martian equator and inside the solar system’s largest known canyon, Valles Marineris.

The map to the right, reduced to post here, provides all the important data. From its caption:

The coloured scale at the bottom of the frame shows the amount of ‘water-equivalent hydrogen’ (WEH) by weight (wt%). As reflected on these scales, the purple contours in the centre of this figure show the most water-rich region. In the area marked with a ‘C’, up to 40% of the near-surface material appears to be composed of water (by weight). The area marked ‘C’ is about the size of the Netherlands and overlaps with the deep valleys of Candor Chaos, part of the canyon system considered promising in our hunt for water on Mars.

What the caption does not note is the latitude of this hydrogen, about 3 to 10 degrees south latitude. Assuming the hydrogen represents underground ice, this would be the first detection on Mars below 30 degrees latitude, and the very first in the equatorial regions. Data from orbit has suggested that Mars has a lot of water ice, found near the surface more and more as you move into higher latitudes above 30 degrees and making Mars much like Antarctica. Almost no ice however had until now been detected below 30 degrees latitude. As the European Space Agency’s press release noted,
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Visible clean water ice on Mars

December 15, 2021 11:57 am Robert Zimmerman

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Cool image time! The photo to the right, cropped and reduced to post here, is today’s picture of the day for the high resolution camera on Mars Reconnaissance Orbiter (MRO). Taken on September 13, 2021, it shows an exposed scarp on the southern inner wall of a small 800-foot-wide crater.

What makes that scarp intriguing is its blue color. As noted by Shane Byrne of the Lunar and Planetary Lab University of Arizona, who wrote the caption:

This north-facing cliff appears to expose icy material that’s similar to other pole-facing scarps showing buried ice elsewhere on the planet. These cliffs give us a cut-away view of the buried ice in that location and can help answer questions about what the Martian climate was like when this ice formed.

The crater itself sits inside a much larger crater, as shown in the wider picture below.
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Curiosity looks back at its entire journey

December 13, 2021 10:03 am Robert Zimmerman

Click for high resolution mosaic. Original images here, here, here, and here.

Click for interactive map.

Cool image time! The mosaic above was created from four photos taken by Curiosity’s left navigation camera on December 12, 2021, just after the rover had moved into Maria Gordon Notch. The view is to the north, looking back at the rover’s journey climbing up the floor of Gale Crater into the foothills of Mount Sharp. The rim of Gale Crater can be seen about 25 to 30 miles away.

The cliff in shadow on the left is about 40 feet high. The cliff in sunlight on the right is between 30 to 60 feet high, depending on where you measure.

The overview map to the right shows Curiosity’s entire journey, with the yellow lines indicating the approximate area covered by the mosaic above. All told the rover has climbed about 1,700 feet since it landed. While much of the rover’s route is blocked from our view by the cliffs on left, the nearest sand dune sea in the center of the mosaic is the one that the rover circled around from January 2021 to June 2021.
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Curiosity takes a close look at a Martian cliff

December 9, 2021 11:15 am Robert Zimmerman

Click for full resolution. Original images here and here.

Curiosity has now moved up and into Maria Gordon Notch, a gap in the mountains of Gale Crater that is about forty feet wide, with a 40-foot-high cliff on its western side and a 30 to 60 foot cliff on its eastern side.

The mosaic above, created from two navigation camera images, looks up at the top half of that western cliff. Note the many many layers, each one of which records some climate or volcanic event in Mars’ geological history. The Mars we see today took a long time and many events to become what it is. Such layers however have not been seen everywhere by Curiosity. Compare for example this layered cliff with the massive outcrop dubbed Siccar Point and looked at closely by the rover in October. In that outcrop the layers were either non-existent, or merged together during some subsequent geological process.

Note also the pond of sand/dust at the center-bottom, nestled in a hollow but sitting almost vertical. That the dust can maintain itself at such an angle illustrates Mars’ lighter gravity, about 39% of Earth’s, which in turn allows for a much steeper angle of repose. That lighter gravity also allows for some sections of rock to stick out more precariously than possible on Earth.

As Curiosity moves through the notch in the next few days, more such cool pictures will become available, and I shall post them.

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Strange eroded glacial flows in unnamed crater on Mars

December 8, 2021 12:20 pm Robert Zimmerman

Click for full resolution image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on November 1, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a series of strange glacial-like flows coming off the western slopes of the central peak of a 40-mile-wide unnamed crater, located smack dab in what I call Mars’ glacier country, that 2,000 long mid-latitude strip where almost every image shows evidence of glaciers.

The cropped section to the right doesn’t really do these strange flows justice. Make sure you click on the image to see the full resolution version. There are numerous separate flows coming off that central peak. Each appears to show that as time passed, each flow traveled a shorter distance down the mountain, leaving a moraine behind at higher and higher points.

The overview map below provides the context.
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Where Ingenuity and Perseverance presently sit in Jezero Crater

December 8, 2021 9:15 am Robert Zimmerman

Click for interactive map.

The map to the right, annotated to post here, shows the present location of the rover Perseverance (the red dot) in relation to the 17th flight of the helicopter Ingenuity (indicated by the green line and dot) that successfully occurred on December 5, 2021.

Perseverance has been very very very very slowly retreating south, following the same route it took to move into the rough sand dune region the scientists have dubbed Seitah. Based on their long term plans, the rover will retrace its path (the white dotted line) to its landing site, and then continue along the yellow dashed line to eventually reach the base of the delta, dubbed Three Forks, that in the distant past poured through a gap in the rim of Jezero Crater.

The helicopter meanwhile is also retracing its flights, heading north to the spot where Perseverance first placed it on the ground. Because of the seasonally thinner atmosphere, the helicopter’s flights during that return journey must be shorter, which is why the 17th flight only traveled halfway across Seitah. In crossing it the first time it had done so in one flight. Now it will take two.

During that 17th flight it appears that the topography between the rover and the helicopter’s landing site caused a loss of communications as the helicopter was landing.

The Ingenuity team believes the 13-foot (4-meter) height difference between the Perseverance rover and the top of Bras [an outcrop] contributed to the loss of communications when the helicopter descended toward the surface at the end of its flight.

That loss of communications apparently caused no problems, but it will likely mean that Ingenuity will do no more flights until Perseverance can get closer and better positioned.

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Curiosity moves into a mountain gap

December 7, 2021 10:51 am Robert Zimmerman

Click for full resolution version. Original images here and here.

Click for interactive map.

For the last three weeks the Curiosity science team has had the rover poking about at the base of the 40 foot cliff on the right of the panorama above. At that location many rocks and boulders had fallen from the top of the cliff, which gave them an opportunity to study the geology of the plateau above, even though it was literally beyond reach.

Beginning yesterday that work ended, and the science team finally made the commitment to move forward, into the gap above where the rover will turn right, climb up onto that plateau through a notch they have dubbed Maria Gordon Notch. The map to the right shows this coming route with the red dotted line.

Once in that notch Curiosity will truly be in the mountains of Gale Crater, even if those mountains are only the foothills to Mount Sharp.

It is interesting to contrast the roughness of the terrain that Curiosity is now routinely traveling, with the relatively benign ground that Perseverance is traversing on the floor of Jezero Crater. While Curiosity is pushing forward into steeper and rougher terrain, the Perseverance team is retreating from the somewhat mild sand dune ground of South Seitah, even though that ground is far less challenging than anything faced by Curiosity. You can see this retreat at the interactive map here. Zoom in and place your cursor over each waypoint. Rather than push forward, the Perseverance team seems willing to have the rover retreat and retrace its route around Seitah, even though to retrace those steps will likely take a few weeks, during which they will cover no new ground and will likely learn little new.

Why the Perseverance team seems so timid is puzzling. It could be they are still working out the kinks of their operation. It could be that they want to take no risks at all this early in their mission. And it could also be that the team culture at Perseverance is simply less daring than that of the Curiosity team.

Only time will answer this question. I suspect as the Perseverance mission unfolds its scientists will become more bold. We just need to give them time.

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