Tag Archives: geology

Changing Mars

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

Dune slope, with grooves, in Russell Crater
Click for full image.

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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Enigmas on Mars

Enigmas on Mars
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Cool image time! The photo on the right, cropped and reduced to post here, is a perfect example of the difficulty of explaining the alien landscapes on Mars, based on orbital imagery. It was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on January 23, 2020.

In this one image alone we have the following strange features, all within an area about 8 by 11 miles in size:

  • Several small very obvious pedestal craters (near the top right), some located inside depressions. Pedestal craters are created because the surrounding terrain eroded away around them. Since these are pedestals, however, why are they also inside depressions?
  • Two large circular mesas that appear to vaguely have terraced erosion. These might also be pedestal craters, but maybe not. They also sit much higher than the pedestal craters above. Either way, the mesas remained while the terrain around them eroded away.
  • Several normal craters with a series of circular features within each. At this latitude, 34 degrees south, it is possible these craters are filled with buried ice, what scientists call concentric crater filled glaciers.
  • A light-colored string of ridges aligned to almost look like a kite with tail. The light color says this ridge is not made up of the same material as the circular mesas and pedestal craters, but it too was not eroded away.
  • A number of small bean-shaped depressions (just south of the biggest circular mesa and near the top left). Don’t ask me what caused them. I have no idea.

Overview map

The spot is located in the Martian southern cratered highlands, as shown by the blue cross in the overview map to the right. Complicating its geological history is that it sits inside a very gigantic very old and degraded crater, with numerous newer smaller impacts overlaid on top. Any explanation needs to include these impacts, and the ejecta from them.

If you click on the image and study the full resolution photograph, you can find even more enigmatic features. For most there is a reasonable geological theory. Putting them all in one place and somehow getting all those different explanations to fit together however is far more difficult.

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Triple impact on Moon

Impact craters Messier and Messier A on the Moon

Cool image time! A new image release from Lunar Reconnaissance Orbiter (LRO) takes a look at the impact process that created the crater Messier and its neighbor crater Messier A. The photo to the right, cropped to post here, shows both craters.

Take a close look at Messier A. It is actually a double crater itself. From the release:

Messier A crater, located in Mare Fecunditatis, presents an interesting puzzle. The main crater is beautifully preserved, with a solidified pond of impact melt resting in its floor. But there is another impact crater beneath and just to the west of Messier A. This more subdued and degraded impact crater clearly formed first.

Did these three craters happen as separate events. According to the data, it appears no. Instead, they might have all been part of a single rain of asteroids, all occurring in seconds.
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In the midst of Mars’ volcano country

lava channel
Click for full image.

Cool image time! While the rest of the world is entirely focused on panic and disease, I am going to go on with my life. The photo to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on December 26, 2019. I suspected this channel was lava, and when I asked Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona, he confirmed my suspicion.

Yes, that surface appears to be lava–it is part of the Elysium plains, which have many geologically-young lava flows. It’s likely that the channel is a lava channel, and the surrounding plains may be from an earlier stage of the same eruption.

The entire surface of the channel and the surrounding plains appear very fresh, mostly because of their smoothness and lack of many craters. You can also see what looks like a recent impact (the small dark splotch near the left edge about two-thirds from the top).

The fresh and smooth look of Elysium Planitia generally has led scientists to conclude that much of this region is formed from lava flows, some relatively recently. Thus, this particular lava channel is smack dab in the middle of Mars’ volcano country, quite vast and extensive. The context map below illustrates this.
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Quick fading of a Martian impact crater

Fresh impact crater on Mars, in 2010
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The same impact, four Martian years later.
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Cool image time! Though it seems that no one is really interested in anything but the Wuhan virus and the attempt by our corrupt politicians to use it to gain power, I think that life requires more from us than politics and panic. Thus, I am going to keep posting pure science and cool images.

The two photos to the right were taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) almost ten years apart. They were both posted as captioned images, the first in 2010, the second on March 19, 2020 to illustrate the remarkable fading of a fresh impact’s dark ejecta, in only about four Martian years.

The March 19, 2020 captioned image included an animation to illustrate the change. I prefer putting the two images side-by-side. Either way, the change is striking. As planetary scientist Alfred McEwen noted in his caption, “the dark material has faded into the background, while the new 6.3-meter diameter crater persists.”

Wind and dust storms probably acted to wipe out the dark material, but the process did not take that long, and last year’s global dust storm was not a major factor, since much of the dark material was already gone in this July 2012 image.

The crater itself is located in Arcadia Planitia, just west of the Erebus Mountains, the very region in the northern lowlands that SpaceX has made its primary candidate landing site for its Starship rocket, partly because the terrain is flat which makes landing easy, and partly because there is amply evidence that these lowlands have lots of ice just below the surface. And the full image for the 2019 photo reinforces this conclusion. Much of the rougher ground south of the impact appears to be the partially sublimated surface of an ice block.

So, while this region will provide an easy smooth landing site and plenty of water for the first human arrivals, those humans will also have to contend with a planet without a thick atmosphere to protect them from most meteorites. Rare as these events are, they happen more often because of Mars’ location closer to the asteroid belt, and they hit the surface far more frequently.

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Mars: Volcanic, Glacial, or Fluvial?

Sinuous ridge on Mars
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Cool image time! The photograph on the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on September 30, 2019. It shows what the image title dubs a “sinuous ridge” in a region called Tempe Terra.

What caused it? At first glance the meandering nature of the ridge suggests it was originally a riverbed, formed by flowing water. Eventually the water dried up, and because that riverbed was made of harder material than the surrounding terrain, long term erosion caused that surrounding terrain to wear away, leaving a raised ridge where the river used to be. Scientists have found many such inverted channels on Mars.

Not so fast!
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Martian plateaus and buttes

Martian plateaus and buttes
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Cool image time! Rather than sit in cowering fear, as it appears too many worldwide are doing, I am going to stay calm and carry on. The photo to the right, rotated, cropped, and reduced in resolution to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on January 20, 2020. It shows a small section of a region dubbed Iani Chaos, a terrain dubbed such by scientists because of its cracked and chaotic nature, flat-topped mesas cut by canyons and fissures.

Chaos terrain is generally found in the transition zones on Mars between its southern highlands and northern lowlands. It was formed over time by erosion processes, either liquid water or ice, that slowly washed out the material along fault-lines, leaving mesas behind. This particular spot in Iani Chaos appears to be late in this process, with the gaps between the buttes wide and many of the mesas worn down into pointy knobs.

The location of Iani Chaos, as shown in the map below, tells us much about its history.
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Inactive hot springs on Mars?

Inactive hot springs on Mars?
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Overview of Vernal Crater

Cool image time! In prepping my report of the interesting abstracts from Friday of the cancelled 51st annual Lunar & Planetary Science conference (to be posted later today), I found myself reading an abstract [pdf] from the astrobiology session about the possibility of now inactive hot springs on Mars! This was such a cool image and possibility I decided to post it separately, first.

The top image to the right, cropped and expanded to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter in 2009. It shows some dark elliptical splotches inside the floor of a crater dubbed Vernal. The second image to the right, taken from the abstract, shows the context, with the top image a wide shot showing the southern half of Vernal Crater where these features are located, and the bottom image zooming into the area of interest. The white box focuses on the elliptical features seen in the first image above. From the abstract:

The elliptical features consist of concentric halos of high but varying albedo, where the highest albedo in each occurs in a small central zone that mimics the shape of the larger anomaly. Each feature is also traversed by circumferential fractures. Several similar tonal features extend for 5-6 km, on stratigraphic trend with the elliptical features. Hypotheses considered for the origin of the elliptical features included springs, mud/lava volcanoes, pingos, and effects of aeolian erosion, ice sublimation, or dust, but the springs alternative was most compatible with all the data.

The abstract theorizes that the small ligher central zone is where hot water might have erupted as “focused fluid injection” (like a geyser), spraying the surround area to form the dark ellipses.

I must emphasize that this hypothesis seems to me very tenuous. We do not really have enough data to really conclude these features come from a formerly active hot spring or geyser, though that certainly could be an explanation. In any case, the geology is quite intriguing, and mysterious enough to justify further research and even a future low cost mission, such as small helicopter drone, when many such missions can be launched frequently and cheaply.

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Black dunes and weird hills on Mars

Black dunes and weird hills on Mars
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Cool image time! Or I should say a bunch of cool images! The photo on the right, rotated, cropped, reduced, and annotated by me, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on February 3, 2020. An uncaptioned image, it was entitled “Arabia Terra with Stair-Stepped Hills and Dark Dunes.” Arabia Terra is one of the largest regions of the transition zone on Mars between the northern lowland plains and the southern cratered highlands. It is also where Opportunity landed, and where Europe’s Rosalind Franklin rover will land, in 2022.

This image has so many weird and strange features, I decided to show them all, Below are the three areas indicated by the white boxes, at full resolution. One shows the black dunes, almost certainly made up of sand ground from volcanic ash spewed from a long ago volcanic eruption on Mars.
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Martian dust devil tracks come and go

The changing surface of dunes on Mars
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Earlier image of the same dunes
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Cool image time! To understand what created the vastly strange and alien Martian surface, it will be necessary for scientists to monitor that surface closely for decades, if not centuries. To the right is one small example. Taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) and rotated, cropped, and reduced to post here, it shows a dune field inside a crater in the southern cratered highlands of Mars. Craters have been found to be great traps for dust and sand on Mars. Once the material is blown inside, the winds are not strong enough to lift the material out above the surrounding rims. Thus you often get giant dunes inside craters, as we see here.

What makes this location of interest to planetary scientists is the changing surface of these dunes. They have been monitoring the location since 2009. In 2013, the MRO science team released a captioned photograph, the second image to the right, also rotated, cropped, and reduced by me to match the same area in the top image. In that caption planetary scientist Corwin Atwood-Stone of the Lunar and Planetary Laboratory in Arizona wrote,

This area was previously imaged in August 2009, about two Mars years ago, and in that image dust devil tracks were also visible. However the tracks visible now are completely different from the earlier ones. This tells us that there has been at least one dust storm since then to erase the old tracks, and lots of dust devil activity to create the new ones.

Since then the MRO science team has taken repeated images of this location to monitor how the dust devil tracks change, as well as monitor possible changes to the dunes themselves, including avalanches. The newest image above shows the result of the global dust storm last year. It wiped out the dust devil tracks entirely.

The newer image was entitled, “Monitor Dune Avalanche Slopes,” but I couldn’t find any examples. Based on published research, I am sure there is something there, even if I couldn’t find them. Maybe my readers have a better eye than I.

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Martian badlands

The Tyrrhena Terra badlands
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The photo to the right is a small section cropped from an image taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on January 2, 2020. It shows the rough, cratered southern highlands dubbed Tyrrhena Terra that lie between the low Isidis Basin to the north and Mars’ deepest basin, Hellas, to the south.

The image was taken not because any specific scientific request, but because MRO was doing spectroscopy over this area and it made sense to also take a photograph. Comparing the photograph with the spectroscopic data allows scientists to better understand that spectroscopy.

The white cross in the map below shows the location of this image. The map itself covers latitudes from 40 degrees north to 55 degrees south.
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Curiosity reaches highest point yet on Mars

Curiosity looking north across Gale Crater
Click for full resolution version.

Time for some more cool images! The panorama above, cropped and reduced to post here, was assembled from images taken by Curiosity on March 6, 2020 by its left navigation camera, just after it topped the slope and settled on the very rocky plateau of what the scientists have dubbed the Greenheugh Piedmont, the highest point on Mars that Curiosity has so far traveled. It looks north, across Gale Crater to its far rim, about thirty miles away. That rim rises about a mile higher than where Curiosity sits today.

To quote Michelle Minitti, the planetary geologist who wrote the update describing this achievement:

Kudos to our rover drivers for making it up the steep, sandy slope below the “Greenheugh pediment” (visible in the [right] side of the above image) and delivering us to a stretch of geology we had our eyes on even before we landed in Gale crater!

The panorama below is also assembled from photos taken by the left navigation camera, but this time it looks south, across the piedmont toward Mt. Sharp. Its view of the the piedmont’s very very rough terrain I think proves that once the scientists have gathered their data from this point, the rover will descend back down and resume its original route, circling the piedmont to skirt its southern edge where orbital data suggests the going will be smoother.
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Rolling boulders on Mars

Boulder tracks on Mars
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Cool image time! The photo to the left, cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on January 21, 2020, and shows several boulders at the bottom of a slope, along with the tracks those boulders made as they rolled downhill sometime in the far past.

Uphill is to the south. We know the dark spots at the end of these tracks are large boulders partly because of the wind streaks emanating away from them to the north. As the wind goes around each rock it produces eddies that produce the tracks. Based on the scale and the image resolution (about 10 inches per pixel), these boulders range in size from about one to five feet in diameter.

This image has two points of interest. First, the tracks left by the boulders seem to have a repeating pattern. My guess is that the pattern most likely formed because the boulders are not spherical in shape, and as they rolled each roll repeated a certain pattern reflecting that shape. This theory is reinforced by a close look at each boulder. Though the resolution is insufficient to resolve the boulders themselves, the pixel distribution for each strongly suggests an asymmetric shape.

Second, this image, when compared with an earlier MRO image of the same spot, taken fourteen years ago in December 2006, shows no obvious change. These tracks, and their boulders, have therefore probably sat here, as we see them, for a long time. Since there appear to be two sets of tracks, with one overlying the other, this suggests that two separate events (an earthquake or nearby impact) each time caused a bunch of boulders to break free and roll downward together, with the second set of boulder tracks crossing over the earlier set.

Establishing when those two events occurred, however, will require some on-site data, something that will likely not occur until humans roam the surface of Mars in large numbers.

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Mars rover Update: March 4, 2020

Panorama looking south and uphill
Click for full resolution.

Curiosity

[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.]

Map of Curiosity's travels

Since my last rover update on January 13, 2020, Curiosity has finally moved on from the base of Western butte, where it spent more than a month drilling a hole and gathering a great deal of geological data. Rather than head downhill and around the plateau and back to its planned route (as indicated by the red line in the map to the right), the Curiosity science team decided to push upward and onto the Greenheugh Piedmont (as indicated by the yellow line).

They had always planned to reach the top of this plateau, but not for several years. First they were going to head east to study a recurring slope lineae (see my October 2019 update), an example of a dark streak that darkens and fades seasonally and could provide evidence of water seepage from below ground.

Instead, they decided the close proximity of the top of the piedmont and its geology was too tempting. The piedmont is apparently made up of a layer that is very structurally weak, and breaks up easily, as you can see by the panorama above. It also appears to sit on softer, more easily eroded material, which thus accentuates this break up. If you look at the left part of the panorama you can see what I mean. The piedmont layer there is the thin unbroken layer sitting on what looks like sand. As that sand erodes away the layer quickly breaks into small pieces, as shown in the rest of panorama.

Traveling on the piedmont will likely be difficult and threaten Curiosity’s wheels. I suspect this reality prompted them to choose to get to the top and obtain data now, rather than wait several more years of rough travel that might have made access to the piedmont difficult if not impossible.

They presently sit just below the top, and are studying their options before making that last push.
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Summer at the Martian North Pole

Buzzell pedestal crater in context with polar icecap scarp
Cool image time! The image above, cropped, reduced, and brighten-enhanced to post here, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on December 26, 2019 of the dunes just below the 1,500 to 3,000 foot high scarp that marks the edge of the Martian north polar icecap. I have brought up the brightness of the dune area to bring out the details.

This one image shows a range a very active features at the Martian north pole. At this scarp scientists have routinely photographed avalanches every Martian spring, as they have been occurring, caused by the warmth of sunlight hitting this cliff wall and causing large sections to break off. As Shane Byrne of the Lunar and Planetary Lab University of Arizona explained in my September 2019 article,

On Mars half of the images we take in the right season contain an avalanche. There’s one image that has four avalanches going off simultaneously at different parts of the scarp. There must be hundreds to thousands of these events each day.

Buzzell dunes, March 19, 2019
Click for full image.

On the left side of the image is an area of dunes that Candice Hansen of the Planetary Science Institute in Arizona has dubbed “Buzzell.” As spring arrives here, she has MRO regularly take images of this site (as well as about a dozen others) to monitor the changes that occur with the arrival of sunlight on the vast dune seas that surround that polar icecap.

The image to the right zooms in on one particular distinct feature, a pedestal crater, surrounded by dunes, that I have labeled on the image above. This image was taken just as spring began, with the Sun only five degrees above the horizon. At that time the dunes and pedestal crater were mantled by a frozen layer of translucent carbon dioxide that had fallen as dry ice snow during the sunless winter and then sublimates away each Martian summer.

Since March I have periodically posted updates to monitor the disappearance of that CO2 layer. (See for example the posts on August 2019 and November 2019.) Below are two more images, showing the ongoing changes to this area from early to late summer.
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Glacial breakup on Mars

glacial breakup on Mars
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Cool image time! The photograph to the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on December 22, 2019 and was titled “Contact Between Debris Apron and Upper Plains in Deuteronilus Mensae”.

The section of the full image that I have focused on shows what appears to be the downhill break-up of the surface debris covering an underlying water ice glacier. The grade is downhill to the south.

I am confident that this is buried glacial material based on recent research:

Both of these reports found lots of evidence of shallow ice in Deuteronilus Mensae, a region of chaos terrain in the transition zone between the Martian northern lowlands and the southern highlands.

With this image we see what appears to be the slippage of that ice downslope, causing breakage and cracks on the surface, with much of that surface made up of the dust and debris that covers the ice and protects it. Towards the bottom of the image it even appears that the disappearing ice is unveiling the existence of a bunch of buried bedrock mesas, typical of chaos terrain, previously hidden by the ice because it filled the surrounding canyons.

Below is a close-up of the photograph’s most interesting area of break-up.
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Peering into a Martian pit

Peering into a pit
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Cool image time! The science team for the high resolution camera on Mars Reconnaissance Orbiter last week released the above image of a pit to the west of the giant volcanoes Arsia and Pavonis Mons. The left image is without any adjustments in exposure. The right image has brightened the pit’s interior to bring out details in order to see what’s there. As planetary scientist Ross Beyer of Ames Research Center noted in his caption:

The floor of the pit appears to be smooth sand and slopes down to the southeast. The hope was to determine if this was an isolated pit, or if it was a skylight into a tunnel, much like skylights in the lava tubes of Hawai’i. We can’t obviously see any tunnels in the visible walls, but they could be in the other walls that aren’t visible.

Wider view of pit
Click for full image.

Because the image has been rotated 180 degrees, north is down. The northern wall of the pit appears to be either very vertical, or overhung. A tunnel might head north from here, but because of the angle of the photograph, this cannot be confirmed.

To the right is a wider look from the full photograph, showing the surrounding terrain, with north now to the top. In line with this pit is a depression that crosses the east-west canyon to the north. This alignment strongly suggests that a fault or fissure exists here, and that an underground void along this fissure line could exist. It also suggests that a deeper and larger void could exist below that larger canyon.

This pit, and the accompanying fissures, were likely caused by crack-widening along these faults, produced as this volcanic region bulged upward.

Map of knowns pits surrounding Arsia Mons

This pit is also one of the many many pits found near these volcanoes. The map to the right shows by the black boxes all the pits documented by the high resolution camera on MRO in the past few years, with this new pit indicated by the white box.

Beginning in November 2018 until November 2019 I was almost doing a monthly post reporting the new pits photographed by MRO. Since November however the number of new pit images dropped. This is not because every pit has been imaged, but because it appears they have completed their initial survey.

Below is a list of all those previous pit posts:
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Chinese scientists publish radar results from Chang’e-4 lander

Layers as seen below ground by Chang'e-4 radar

The new colonial movement: Chinese scientists today published their first ground-penetrating radar results from their Chang’e-4 lander on the far side of the Moon.

Using a ground-penetrating radar instrument on Chang’e-4, researchers have found that the rover is likely sitting on different layers of ejecta—debris from multiple impacts over time that rained down at high velocities to blanket the lunar surface and now fill the crater. “[We] see a very clear sequence of [layers],” says Elena Pettinelli of Roma Tre University in Italy, one of the paper’s co-authors.

The rover’s radar instrument was able to penetrate up to 40 meters below the surface of the moon, more than twice the distance achieved by its predecessor, the Chang’e-3 mission, which landed on the lunar near side in December 2013. Data from the latest mission show three distinct layers beneath the rover: one made of lunar regolith, or soil, down to 12 meters; another made of a mix of smaller and larger rocks down to 24 meters; and a third with both coarse and fine materials extending the rest of the 40-meter depth.

The figure to the right comes from the paper [pdf] Though the layers have not been dated, their differences suggest different past events in the formation of this surface.

These results are excellent, but they also have many uncertainties. Radar can tell you a lot, but the only way you can really ever know anything about what’s below ground is to go there and actually do some digging.

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Enclosed Martian canyon, filled with ice

Ice-filled canyon on Mars
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Cool image time! The photo on the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on November 21, 2019. The uncaptioned image was simply entitled “Ice-filled Graben.”

The location is on the lower flanks of the giant volcano Alba Mons, which in itself sits north of Olympus Mons and the volcanic Tharsis Bulge. The canyon is called a graben because it was formed when a section of the crust slips downward along parallel faults. It does not have the features of a rill, or lava flow, as it starts and stops suddenly. It probably formed due to the rise of the volcano, pulling apart its flanks along faults, causing some sections then to slip downward.

How do the scientists know this is ice-filled? I suspect they have other data that indicates the presence of water, but there are also clear features inside this canyon that resemble the glacial features found elsewhere on Mars. For example, note the parallel lines near the canyon walls. These indicate past surface levels as well as layers within the ice from cyclic climate processes. The line of pits along the southwest wall, where the surface gets more sunlight, also suggests that this sunlight is causing more ice to sublimate away.

Finally, the graben is located at 46 degrees north latitude, definitely far enough north for such ice to exist, based on ample other research.

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Quakes by InSight indicate Mars’ interior is active

Cerberus Fossae

The first seismic results from InSight’s seismometer now show that the interior of Mars is active, with regular moderately-sized quakes.

The Seismic Experiment for Interior Structure (SEIS) instrument – a seismometer developed by an international consortium under the leadership of the French space agency CNES – recorded a total of 174 seismic events between February and September 2019. Twenty of these marsquakes had a magnitude of between three and four. Quakes of this intensity correspond to weak seismic activity of the kind that occurs repeatedly on Earth in the middle of continental plates, for example in Germany on the southern edge of the Swabian Jura hills.

Although only one measurement station is available, models of wave propagation in the Martian soil have been used to determine the probable source of two of these quakes. It is located in the Cerberus Fossae region, a young volcanic area approximately 1700 kilometres east of the landing site.

Cerberus Fossae is a land of cracks and linear depressions located between the giant volcanoes, Elysium Mons to the north and Olympus Mons to the east. It is believed those fissures were caused by the rise of those volcanoes, stretching the crust and cracking it.

This new data from InSight strengthens this theory.

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Ice-filled canyon on Mars?

The ice-filled head of Mamers Valles
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The image to the right, rotated, cropped and reduced to post here, was taken on December 19, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled “Head of Mamers Valles”, it shows the very end of one side canyon to this very extensive canyon system made up of the fractured fissures and mesas of chaos terrain.

Mamers Valles itself sits in the transition zone between the northern lowland plains and the southern cratered highlands. This specific canyon is close to those lowlands, at a latitude of 40 degrees north, where scientists believe there are many buried inactive glaciers of ice.

The image reinforces this belief. The entire canyon appears practically filled with what looks like ice. In fact, it almost looks like we are looking down at a frozen lake with a layer of snow on top of it. In this case, the layer is not snow, but dust and dirt and debris that covers the ice to protect it and prevent it from sublimating away.

The overview map below shows the location of this canyon, by the red cross, within Mamers Valles.

Mamers Valles

Mamers Valles is actually a very large collection of miscellaneous canyons, flowing into the lowlands. In some areas it looks like very old chaos terrain, with the canyons so eroded that all we see are scattered mesas. In other places the canyons more resemble meandering river canyons sometimes interspersed with crater impacts.

Scientists have analyzed the canyons in Mamers Valles, and from this concluded that they were likely formed from “subsurface hydrologic activity”. which in plain English means that flowing water below ground washed out large underground passages, which eventually grew large enough for their ceilings to collapse and form the canyons we see today.

Yesterday I posted an image of a string of pits that could very well be evidence of this same process in its early stages of canyon formation. In Mamers Valles the process is far more advanced, and the canyons have existed for a long time, long enough for the planet’s inclination to go through several cycles of change, from a low of 25 degrees tilt (what it is now) to has high as 60 degrees. At that high inclination the mid-latitudes were colder than the poles, so that ice would sublimate from the poles to fall as snow in the mid-latitudes, forming active glaciers within canyons such as this.

Now that the planet’s inclination is similar to Earth’s, 25 degrees, the poles are slightly colder than the mid-latitudes, and the glaciers in this canyon are either inactive (if buried) or slowly sublimating away so that the water can return to the poles.

Here however the surface debris appears to be protecting the glaciers, leaving the canyon filled mostly with ice. For future settlers this ice would likely be relatively accessible, and at a latitude where the environment is also relatively mild, for Mars.

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Yutu-2 finds rocks that appear young

Yutu-2 has found a cluster of small rocks that appear relatively young, with little erosion.

The rocks also also appear as if they came from another place on the Moon.

Closer inspection of the rocks by the rover team revealed little erosion, which on the moon is caused by micrometeorites and the huge changes in temperature across long lunar days and nights. That anomaly suggests that the fragments are relatively young. Over time, rocks tend to erode into soils.

The relative brightness of the rocks also indicated they may have originated in an area very different to the one Yutu-2 is exploring.

Youth in this case is very relative. The rocks might be young when compared to the surface on which they sit, but they still could be more than a billion years olf.

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Pits indicating a Martian underground river?

A string of pits suggesting a past underground river system on Mars
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Cool image time! As my regular readers well know, I am a caver, and am thus always interested when the high resolution camera on Mars Reconnaissance Orbiter (MRO) takes a close-up of a pit that might also be an entrance to a cave.

The photo to the right, cropped and reduced to post here, was part of the most recent image release from MRO, but was boringly labeled “Arabia Terra” after the region where it is located, one of the largest transition zones on Mars between the northern lowland plains and the southern cratered highlands. When I took a close look, what I found was an intriguing string of pits whose arrangement is strikingly reminiscent of a river tributary system.

The white box indicates one section that I have zoomed into, as shown below.
» Read more

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Martian wind-swept buried depressions

Wind-swept Martian depressions
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Cool image time! The photo to the right, rotated, cropped and reduced to post here, was taken on January 3, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows three strange teardrop-shaped depressions, clearly wind-swept and partly buried by dust and sand.

The location on Mars of these depressions is in the transition zone between the southern cratered highlands and the northern lowlands. This is also a region dubbed the Medusae Fossae Formation, a region where it appears a great deal of volcanic material was laid down during one or more eruptive events 3 to 3.8 billion years ago.

Whether these depressions were formed during those events is impossible to tell from the available data, especially because the underlying bedrock is buried in dust.

Their shape appears to have been caused as the wind slowly exposed three buried peaks of hard rock. The wind, blowing from the southwest to the northeast, would hit the peaks, producing an downward eddy that would churn out dust from the windward side. The wind and dust would then blow around the peaks, creating the teardrop tail on the leeward side to the northeast.

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Large glacier-filled crater/depression on Mars?

Glacier-filled depression?
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Cool image time! The photograph on the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on December 21, 2019. It shows the eastern half of the floor and interior rim of a large squarish-shaped crater or depression in what seems to be an unnamed region of chaos terrain located in the transition zone between the Martian southern highlands and the northern lowland plains.

The floor of this depression has many of the features that indicate the presence of a buried ice glacier, including flow features on the depression floor, linear parallel grooves, and repeating moraine features at the slope base. In fact, all these features give the strong impression that this crater is ice-filled, to an unknown depth.

Chaos terrain, a jumble of mesas cut by straight canyons, are generally found in this transition zone, and could be an erosion feature produced by the intermittent ocean that some believe once existed in the northern lowlands. Whether or not an ocean lapped against these mesas and created them, this chaos terrain is believed to have been caused by some form of erosion, either wind, water, or ice.

Wide context view

The location is of this chaos terrain in that transition zone is illustrated by the context map to the right. It sits on the edge of the vast Utopia Basin, one of the largest and deepest northern lowland plains. It also sits several hundred miles due north of the planned landing site of the Mars2020 rover in Jezero Crater. There is a lot of chaos terrain in this region, with lots of evidence of buried glaciers flowing off the sides of mesas.

Today’s image, with its numerous features suggesting the presence of a buried glacier filling the depression, reinforces this evidence.

Closer context view, showing the chaos terrain region

What impresses me most about this particular depression — should it be ice-filled — is its size. I estimate from the scale of the image that the depression is about six miles across, somewhat comparable though slightly smaller than the width of the Grand Canyon. And yet, unlike the Canyon it appears to have a wide flat floor across its entire width. The second context map to the right zooms in on this chaos region to show how relatively large the depression is. It would not be hard to spot it from orbit. We don’t know the depth, but even if relatively shallow this depression still holds a heck of a lot of water ice.

While the depression appears like a crater in lower resolution wider photographs, higher resolution images suggest it is not round but squarish. Why is not clear, and unfortunately MRO’s high resolution camera has taken no other images of it. This image was also one of their terrain sample photographs, taken not because of any specific research request, but because they need to use the camera regularly to maintain its temperature. This location, having few previous images, fit this schedule and made sense photographing.

Thus, no one appears to be specifically studying this location, making it a ripe subject for some postdoc student who wants to put their name on some Martian geology.

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The range for exposed ice scarps on Mars keeps growing

Overview of ice scarp locations on Mars

In January 2018 scientists announced the discovery of eight cliffs with visible exposed ice layers in the high mid-latitudes of Mars. At the time, those eight ice scarps were limited to a single crater in the northern hemisphere (Milankovic Crater) and a strip of land in the southern highlands at around latitude 55 degrees south.

In the past two years scientists have been using the high resolution camera on Mars Reconnaissance Orbiter (MRO) to monitor these scarps for changes. So far they have seen none, likely because the changes are below the resolution of the camera.

They have also been able to find more scarps in the southern hemisphere strip beyond that strip at 55 degrees south.

Now they have found more scarps in the northern hemisphere as well, and these are outside Milankovic Crater. As in the south, the new scarps are still all along a latitude strip at about 55 degrees.

The map above shows with the black dots the newer scarps located in the past two years. The scarp to the east of Milankovic Crater is typical of all the other scarps, a steep, pole-facing cliff that seems to be retreating away from the pole..

The scarp to the west of Milankovic Crater is striking in that it is actually a cluster of scarps, all inside a crater in the northern lowland plains. Moreover, these scarps are more indistinct, making them more difficult to identify. According to Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona,
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Remnant moraine on Mars

Remnant moraine on Mars
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Cool image time! Using both Martian orbiters and rovers scientists are increasingly convinced that Mars has lots of buried glaciers in its mid-latitudes. These glaciers are presently either inactive or shrinking, their water ice sublimating away as gas, either escaping into space or transporting to the colder poles.

The image to the right, cropped and reduced to post here, shows some apparent proof of this process. Taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on December 23, 2019, it shows a weird meandering ridge crossing the floor of a crater. The north and south parts of the crater rim are just beyond the cropped image, so that the gullied slope in the image’s lower left is actually a slope coming down from that rim.

My first reaction upon seeing this image was how much that ridge reminded me of the strange rimstone dams you often find on cave floors, formed when calcite in the water condenses out at the edge of the pond and begins to build up a dam over time.

This Martian ridge was certainly not formed by this process. To get a more accurate explanation, I contacted Dan Berman, senior scientist at the Planetary Science Institute in Arizona, who had requested this image. He explained:
» Read more

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A bullseye on Mars

Bullseye crater on Mars
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Cool image time! The photo on the right, cropped and reduced to post here, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on November 30, 2019. It shows a lone crater on the flat northern lowlands of Mars in a region dubbed Arcadia Planitia.

The crater is intriguing because of its concentric ridges and central pit. As this region is known to have a great deal of subsurface water ice, close to the surface, these features were probably caused at impact. My guess is that the ice quickly melted, formed the kind circular ripples you see when you toss a pebble in a pond, but then quickly refroze again, in place.

This location is also of interest in that is it just north of the region that SpaceX considers the prime candidate landing site for its Starship manned spaceship.

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The cliff at the end of Chasma Boreale on Mars

The cliff at the end of Chasma Boreale
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Cool image time! The image to the right, cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on November 15, 2019 during the height of the Martian summer in the northern hemisphere. It shows the scarp of the polar ice cap, looking directly down that scarp at what the MRO image post dubs an “exposure of basal unit”, or the bottom of the cap itself. This suggests that the base of that cliff is no longer ice, but the bedrock below it. If this cliff is similar to other scarps off the polar ice cap it should be at least 1,600 feet tall. It might be more, however, as the elevation difference between the cap and the floor of this basin is estimated by scientists to be more than a mile total.

This scarp however is different than the outer icecap scarps where avalanches occur with great frequency during the spring and summer. Instead, it is located in the heart of the ice cap, at the very end of the gigantic canyon Chasma Boreale that slashes a deep cut into that ice cap, practically cutting it in half.

Overview

The overview map on the right, with the red dot showing where this image is located, illustrates the cutting nature of Chasma Boreale. The canyon itself is 350 miles long with a width of about 75 miles at its beginning and with walls that at some points rising a mile in height.

Scientists theorize this canyon was formed by melting ice from cap that built up at the cap’s base, causing erosion and collapse, with the flow following the grade down hill from this end point out to the lowland plains beyond. It is also possible winds played a part in this process, encouraging the canyon formation.

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