The massive scale of Mars’ biggest canyon

Overview map

The south rim of Valles Marineris
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on May 24, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled merely a “terrain sample” by the camera team, it was likely taken not as part of any particular research project, but to fill a gap in the picture-taking schedule in order to maintain the camera’s proper temperature.

When the camera team needs to do this, they try to pick interesting targets within the required timeframe. Sometimes they succeed, sometimes not. In today’s example, they succeeded quite well. As shown by the overview map above, this picture captures (as indicated by the rectangle) the top of the southern rim of Valles Marineris, the biggest canyon on Mars and quite possibly the biggest in the entire solar system.

For scale, the drop from the rim to the low point in this picture is about 9,000 feet. That’s a 1,000 feet more than the drop from the north rim of the Grand Canyon to the canyon bottom at the Colorado River. In Valles Marineris however our descent has barely begun. To get to the bottom of the southern canyon here you still need to drop 15,000 more feet, for a total descent of 24,000 feet, an elevation change similar to most of the mountains in the Himalayas.

Nor are you yet at the bottom. If you climb over the ridge of 18,000-foot-high mountains that bisect Valles Marineris at this point, you can drop down even further, to a depth 31,000 feet below the southern rim.

Mount Everest is just over 29,000 feet high, which means if placed inside Valles Marineris is peak would still sit 2,000 feet below the rim.

The photo itself highlights part of the erosion process that formed Valles Marineris. This is the dry tropics, so no water was involved in shaping this terrain for many eons. Instead, what appear to be flows within the hollows is alluvial fill, material that over time breaks off and rolls downhill, filling the slopes below. Erosion will grind this material into smaller particles, so given enough time it flows almost like sand.

Cracking terraces in Valles Marineris

Overview map

Cracking terraces in Valles Marineris
Click for original image.

Inset

Today’s cool image returns us to the truly spectacular terrain found on the floor of West Candor Chasma, one of the giant side canyons that form Valles Marineris, the biggest canyon in the solar system, many times larger than the Grand Canyon on Earth.

The picture to the right, cropped, reduced, and sharpened to post here, was taken on January 5, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). On the overview map above its location is indicated by the red dot in the inset. The two green dots mark previous cool images from August 2022 and February 2024.

All three images show the same wild alternating dark and light terracing, suggesting many sedimentary layers like those seen in our Grand Canyon, but enhanced by the different erosion processes of the thin Martian atmosphere and its one-third Earth gravity.

The second image to the right zooms in on the area indicated by the rectangle. What makes this area doubly interesting are the cracks that appear to cut through the terraces. In the north-south crack it also appears that the terraces are now offset on each side of the crack.

Apparently, some event, likely an earthquake that occurred after the terraces formed, caused the ground to rip apart, with the earth shifting sideways on either side. Though the seismometer on the InSight lander detected no major quakes in this region, this image suggests they have occurred here, sometime in the past.

To give you a sense of scale, the canyon’s nearby rim to the west is about 14,000 higher, making that canyon wall two to three times taller than the walls of the Grand Canyon.

Dunes on the floor of Valles Marineris

Overview map

Dunes on the floor of Valles Marineris
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 26, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a field of scattered elongated dunes on a flat older surface with craters and what appear to be smaller ripple dunes (in the lower left). The large elongated dunes tend to be oriented in an east-west manner, while the older tiny ripple dunes appear to have a north-south orientation.

Very clearly the larger dunes appear to be traveling across that flat older surface, though whether there is any documented movement is unknown. Generally (though there are exceptions) scientists have found most of the dunes on Mars to be either inactive, or if they are moving because of the wind that movement is very tiny per year. In this case there is one dark spot on the dunes, near the center of the picture, where it appears a collapse might have occurred, suggesting recent change.

On the center right of the picture is the end point of a long ridgeline extending 10 to 12 miles to the east and rising about 7,300 feet, as shown in the overview map above. The small rectangle in the inset shows the area covered by the photograph.

At the base of that ridgeline can be seen a series of terraces descending to the west, suggesting that this hill might be volcanic in nature, with each terrace indicating a separate lava flow. The location is in the dry equatorial regions, so near-surface ice is likely not an explanation.

In the inset the mountain wall to the north is the large mountain chain that bisects this part of Valles Marineris. It overwhelms this small 7,300-foot-high ridge, rising more than 22,000 feet from these dunes with its high point still one or two thousand feet below the rim of Valles Marineris itself.

Once again, the grand scenery of Mars amazes. Imaging hiking a trail along that ridgeline, with the mountains rising far above you to the north and south.

The steep mountain slopes inside Valles Marineris

Overview map

The steep mountain slopes inside Valles Marineris
Click for full image.

Time for another cool image showing the dramatically steep terrain of Valles Marineris on Mars, the largest known canyon in the solar system. The picture to the right, cropped, reduced, and enhanced to post here, was taken on October 31, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The scientists rightly label this picture “Steep Slopes in West Melas Chasma”. The red dot marks the high point on this ridgeline. The green dot at the upper left marks the lowest point in the picture, about 4,800 feet below the peak. The blue dot on the right edge marks the low point on the ridge’s eastern flank, about 4,600 feet below the peak. The cliff to the east of the peak drops quickly about 1,300 feet in less than a mile.

On the overview map above, the white dot marks the location. The inset is an oblique view, created from a global mosaic of MRO’s context camera images, with the white rectangle indicating approximately the area covered by the picture above.

The immense scale of Valles Marineris must once again be noted. The elevations in this picture are comparable to the descent you make hiking down from the South Rim of the Grand Canyon. They pale however when compared to Valles Marineris. In the inset I have indicated the rim and floor of Valles Marineris in this part of the canyon. The elevation distance between the two is 18,000 feet.

In other words, the canyon to the east of this ridge is quite comparable in size to the Earth’s Grand Canyon, and it is hardly noticeable within the larger canyon of Valles Marineris.

The grand Valles Marineris of Mars

The grand canyon of Mars
Click for original image.

Time for another cool image of the grand canyon of Mars, Valles Marineris. The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on May 24, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small section of the floor of this gigantic canyon, where orbital data has detected light-toned materials. From the caption:

Many of the Valles Marineris canyons, called chasmata, have kilometer-high, light-toned layered mounds made up of sulfate materials. Ius Chasma, near the western end of Valles Marineris, is an exception.

The light-toned deposits here are thinner and occur along both the floor and walls, as we see in this HiRISE image. Additionally, the sulfates are mixed with other minerals like clays and hydrated silica. Scientists are trying to use the combination of mineralogy, morphology, and stratigraphy to understand how the deposits formed in Ius Chasma and why they differ from those found elsewhere in Valles Marineris.

The picture however gives no sense of the monumental terrain that surrounds it.
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The base of the long and deep south rim of Valles Marineris

Overview map

The base of southern slope of Valles Marineris
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on July 14, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), showing the very bottom section of the long and endlessly deep south slopes of Valles Marineris, the largest known canyon in the solar system.

The many layers here are likely evidence of repeated volcanic flood lava events, over several billion years, after which the canyon formed.

On the overview map above the black dot in the southeast section of the area of the canyon dubbed Melas marks this location. The picture’s northeast corner is essentially the floor of Valles Marineris. From this point the elevation gain to the southwest corner of the picture 3.5 miles away is about 3,300 feet.

The rim itself however is far far higher, about fifty miles farther to the southwest and climbing about 22,000 feet more. Along those fifty miles you’d have to also climb over two intervening mountain ranges, one about 4,000 feet high and the second about 6,000 feet high.

Valles Marineris is big, so big it is hard to imagine a canyon this size. It makes many moutain ranges on Earth seem small.

Big mountains everywhere inside Valles Marineris

Big mountains in Valles Marineris
Click for original image.

While the giant canyon Valles Marineris on Mars is known best as the biggest known canyon in the solar system — large enough to cover the continental United States several times over — that size tends to diminish the mountainous nature of its interior. Today’s cool image attempts once again (see for example these earlier posts here, here, here, here, and here) to illustrate that stupendous and mountainous nature.

The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on May 15, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The goal of the picture was to get a better view of the numerous layers of this terraced cliff wall. What I see, however from my tourist’s perspective, is a steep wall that descends almost 4,500 feet from the high to the low point in just over three miles. This is as steep if not steeper than the walls of the Grand Canyon.
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An avalanche in the West Virginia of Mars

An avalanche in the West Virginia of Mars
Click for original image.

Cool image time! The picture to the right, rotated, cropped, and reduced to post here, was taken on June 27, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

I have cropped it to focus on this one hill, about 900 feet high (though the elevation data from MRO is somewhat uncertain at this resolution), because of that major landslide on its northern slopes. At some point in the past a major piece of the exposed bedrock at the top broke off and slide about halfway down the mountain, almost as a unit, settling on the alluvial fill that comprises the bottom half of the hill’s flanks.

The bedrock surrounding the peak is also of interest because of its gullies, all of which were created by downward flowing material. Was it ice? Water? Sand? Or maybe a combination of two or three? If water or ice was involved it was a very long time ago, as this location is in the dry equatorial regions of Mars. There is little known near-surface ice here.
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Unknown Mars

MRO context camera mosaic
Click for interactive global mosaic.

Cool image time! The picture to the right was created from a global mosaic of all the context camera images taken by Mars Reconnaissance Orbiter (MRO) since it entered Mars orbit in 2006. It shows an unnamed 17-mile-wide-depression located only about seven miles south of the southern rim of Valles Marineris.

I highlight this particular depression because, despite seventeen years in orbit, MRO’s high resolution camera has at this time still not taken any pictures inside or around it. This is a place on Mars that remains unstudied in detail, in any way, even though its depth is comparable to the Grand Canyon and its features strongly suggest its is a collapse feature, created when the roof over an underground void gave way. If so, it suggests an origin for Valles Marineris that conflicts with present theories.
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Another look at the vastness of Valles Marineris on Mars

The vast Valles Marineris
Click for interactive map.

This week I have returned several times to the giant Valles Marineris canyon on Mars in an attempt to capture its incomprehensible and glorious scale. Without question this canyon is going to become one of the prime tourist spots when humans begin living and working throughout the solar system. Fortunately, its vast size will mean that it will take many many centuries before it even becomes close to crowded there.

Today I try a different approach, using the global mosaic created by scientists at Caltech from the context camera images taken by Mar Reconnaissance Orbiter (MRO). That mosaic processes the images to allow one to see the surface from an oblique angle. The picture to the right covers one small part of the eastern end of Valles Marineris (the white rectangle in the inset), but though small the scale once again is gigantic.

The three white dots are our reference points, one on the north rim, one on the south, and one in the middle on the peak of that central mountain chain. Beginning from the south, the distance from the rim to the middle mountain peak is 43 miles, with the elevation dropping almost 13,000 feet to the floor of the south canyon, than rising almost 10,000 feet to the middle peak. The northern canyon is smaller. From the peak to the north rim is 27 miles, dropping about 9,300 feet and then rising about 8,500 feet to the north rim.

From rim to rim the distance is about 70 miles. Since the middle mountain chain about 18 miles wide, it fills only about 25% of the entire canyon.

In every case, the Grand Canyon would be merely be a small side canyon here. The depths are twice as deep, and the distances are many times larger. In width alone at this point Valles Marineris is seven times wider than the widest part of the Grand Canyon, and this is by far not Valles Marineris’s widest point.
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More sightseeing in Valles Marineris on Mars

More sightseeing on a mesa in Valles Marineris
Click for original image.

The opportunity to see more mind-blowing examples of spectacular views on Mars compels me to post another great view of a mesatop within Valles Marineris, the biggest known canyon in the solar system. The picture to the right, rotated, cropped, and reduced to post here, was taken on May 14, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows an 800-foot-high mesa with two points at its end, the cliff wall below highlighted by numerous layers, many alternating between light and dark material.

The erosion features on the top of the mesa suggests some flow down its middle and into the gap between its two end points. This is the dry equatorial region of Mars, so no near surface water is presently found. In the far past maybe ice, or theorized catastrophic floods of water, caused this erosion.
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Exploring just one small corner of Valles Marineris, Mars’ Grand Canyon

One corner of Valles Marineris
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on February 19, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the many many many layers that are found in the cliffs of Valles Marineris, the largest known canyon in the solar system and far far larger that Earth’s Grand Canyon.

The elevation difference between the red dots is just under 4,000 feet. Yet that high point is still more than 7,000 feet below the rim of the canyon, more than thirty miles to the south. And the lower dot is still about 18,000 feet above the low point in this side canyon of Valles Marineris, about thirty miles away to the northeast.

In other words, in sixty miles from rim to floor the canyon at this location drops about 25,000 feet, only 4,000 feet less than the height of Mount Everest. Compare that with the Grand Canyon’s slopes, which drops in eleven miles about 5,000 feet, beginning at the main south rim lookout at the start of Bright Angel trail.
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Dramatic layers in Valles Marineris

Dramatic layers in Valles Marineris
Click for original image.

Cool image time! The picture to the right, rotated, cropped, and sharpened to post here, was taken on December 28, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows one tiny section of the interior slope of the giant Martian canyon Valles Marineris.

The while layers are not made of frost or ice, because they are light tan, as per the color image. Thus, the alternating layers of dark and light indicate different layering events. The dark layers are probably major lava flood events with a lot of dark ash intermixed, while the tan layers were flood lava events with little dark ash.

The dark lines that cut across these layers are ripple dunes formed from dust that has accumulated inside Valles Marineris.
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Martian helicopters of the future

Today Bob Balaram, the chief engineer for the Mars helicopter Ingenuity, wrote up a short essay summarizing the helicopter’s successes on Mars.

This aircraft, very much also a spacecraft, has been on its own on the surface of Mars, detached from its traveling companion Perseverance, for over 500 Martian days or sols. It has operated way beyond its original planned mission of 30 sols, including surviving a brutal winter that it was not designed for. With 33 flights, almost an hour of flight time, over 7 km of travel in Jezero crater, takeoffs and landings from 25 airfields, almost 4000 navigation camera images, and 200 high-resolution color images, it has proven its worth as a scout for both scientists and rover planners. Currently, it is getting ready to use its fourth software update – this one with advanced navigation capabilities that will allow it to safely fly up the steep terrain of the Jezero river delta, scouting ahead of the rover Perseverance as it searches for signs of past life on Mars. [emphasis mine]

I have highlighted the number of flights above because Ingenuity was supposed to do a very short 34th flight on November 10th that would only have the helicopter go straight up 16 feet, hover, and then come straight back down. Yet, I have seen no postflight reports, and Ingenuity’s flight log still does not include it as of today. One image from Ingenuity that was taken on November 9th has been released, and shows the ground directly below it. No other recent images of this 34th flight however have been released.

The flight could still have happened, or was scrubbed for a later time. What is important however is all those other 33 flights, and what Ingenuity’s overall success has meant for future Martian exploration. As Balaram writes,
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Swirls and mesas in Valles Marineris

Swirls and mesas in Valles Marineris
Click for full image. For the original of the inset go here.

Cool image time! The picture to the right, rotated and cropped to post here, was taken on June 13, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as “fractures in West Candor Chasma,” one of the side canyons that form Mars’ gigantic Valles Marineris, the largest canyon system known in the solar system.

To my eye, I don’t see fractures as much as swirling and curving outcrop ridges, as if the twisted layering here is so steeply tilted so that it is almost vertical, with the more resistant edges sticking up out of the dust and dunes. The color corrected inset zooms in on some of these swirls, though this better view hardly clarifies things. Note how the upper curves seem to suddenly cut off, almost as if someone had sliced them with a knife. Don’t ask me to explain.

The overview map shows us where this spot is within Valles Marineris.
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From the rim to the floor of Valles Marineris

Overview map

From the rim to the floor of Valles Marineris
Click for full image.

For today’s cool Martian image, we begin from afar and zoom in. The overview map above shows the solar system’s largest canyon, Valles Marineris, 1,500 miles long, and 400 miles wide at its widest. The white dot on the north rim of the section of the canyon dubbed Melas marks the location of the photo to the right, rotated, cropped and reduced to post here and taken on January 28, 2011 by the wide angle context camera on Mars Reconnaissance Orbiter (MRO).

I have added elevation numbers to this picture to give it some understandable scale. From the rim to the interior canyon floor — a distance of about ten miles — the canyon wall drops about 19,000 feet. Compare this with Bright Angel Trail in the Grand Canyon, which from the rim to the Colorado River drops about 4,400 feet in about the same distance. The wall of Valles Marineris is about four times steeper.

Even that doesn’t give you the full scale. Having hiked down to that interior canyon floor, you are still about 10,000 feet above Valles Marineris’s main canyon floor, with fifteen more miles of hiking to go to reach it.

The white rectangle marks the area covered by the MRO high resolution image below.
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Engineers propose flying gliders on Mars

Proposed sailplane flights in Valles Marineris
Proposed sailplane flights in Valles Marineris. Click for full image.

Engineers at the University of Arizona are developing a prototype sailplane that they think could fly for long distances on Mars at higher altitudes than a helicopter and not be reliant on solar batteries.

Using dynamic soaring, the sailplane utilises increases in horizontal wind speed with gaining altitude to continue flying long distances. It’s the same process albatrosses use to fly long distances without flapping their wings and expending crucial energy.

After lifting themselves up into fast, high-altitude air, albatrosses then turn their bodies to descend rapidly into regions of slower, low-altitude air. With the force of gravity providing downward acceleration, the albatross uses this momentum to slingshot itself back to higher altitudes. Continuously repeating this process enables albatross and other seabird species to cover thousands of kilometres of ocean, flap-free.

It’s the inspiration for the sailplane’s own propulsion system, enabling it to cover the canyons and volcanoes dotted across the red planet currently inaccessible to Mars rovers.

The graphic above, figure 1 from the engineers’ research paper, shows one possible sailplane mission, deploying two gliders, one to observe the canyon wall and a second to survey the canyon floor. Both would become a weather station upon landing. While the paper doesn’t state a Mars location for this concept, the graphic strikes a strong resemblance to the section of Valles Marineris where scientists have recently taken “Mars Helicopter” high resolution images using Mars Reconnaissance Orbiter (MRO). This paper and those images might be related, or they could be illustrating the general interest by many scientists for this Mars’ location.

Regardless, the engineers are now planning test flights at 15,000 feet elevation, an elevation that will most closely simulate the atmosphere of Mars, on Earth.

Has work begun on a dedicated helicopter mission to Mars?

Overview map

The easternmost point in the Mars Helicopter traverse
Click for full image.

In my routine searches through the image archive for the high resolution camera on Mars Reconnaissance Orbiter, I recently came upon several images labeled “Candidate Mars Science Helicopter Traverse” that I at first thought referred to Ingenuity’s extended mission in Jezero Crater.

A closer look however revealed these photos have nothing to do with Ingenuity or Jezero Crater. Taken in November ’21, January ’22, and March ’22, the images instead cover parts of the south rim of Valles Marineris, the solar system’s largest canyon, and appear to be research for a future dedicated Mars helicopter mission. The overview map above shows the location of these photos by the black dots. Three locations have each been imaged twice to produce a stereoscopic view that can precisely measure the topography.

The photo to the right, cropped and reduced to post here, shows the easternmost image, taken November 3, 2021. Not only does it show ample flat areas, the picture captures an impressive avalanche flow coming down from that southern interior canyon slope.

All the images were requested by planetary scientist Edwin Kite of the University of Chicago. Though I tried several times to contact Dr. Kite to get more information, he unfortunately did not respond. It could be this work is still too preliminary and thus he does not wish to comment.

Nonetheless, the extent of the three sets of images give us a fair idea of the kind of missions Kite and others might be considering. From east to west the distance between the images is about four hundred miles, and covers a traverse of the southern interior slopes of Valles Marineris along that entire length. The photos look mostly at the base of the canyon’s slope, each showing clearly that a helicopter flying there would have plenty of landing spots.

Obviously this first dedicated Mars helicopter mission might not cover this entire distance. Right now these images could simply be the first tentative research on choosing potential landing areas. Regardless, it appears that at least one scientist has already concluded that Ingenuity has proven such helicopter missions make sense, and is beginning to target one of Mars’s most spectacular locations, Valles Marineris, for that mission.

A high mountain inside Valles Marineris

A high mountain inside Valles Marineris
Click for full image.

Cool image time! The photo to the right, cropped, reduced, and annotated to post here, was taken on January 4, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the flat top of a mountain inside Candor Chasma, one of the side canyons of the solar system’s largest canyon, Valles Marineris.

The image was taken when the sun was about 32 degrees above the horizon, to the west, and thus apparently low enough to put the flat top mostly in shadow.

What is most spectacular about this photo is the sense of scale it portrays once you know the overall context. Note the many layered slope to the west. That slope will continue downward far beyond the left edge of this image, dropping for dozens of miles and about 13,000 feet. The overview map below makes this clearer.
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Mountains, Mesas, and Box Canyons on the floor of Valles Marineris

Mountains, Mesas, and Box Canyons
Click for full image.

Overview map

Cool image time! The photo above, cropped, reduced, and rotated to post here, was taken on March 12, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small section of the floor of the giant 2,550-mile-long and 400-mile-wide Valles Marineris canyon on Mars. In fact, this section, as indicated by the black rectangle in the overview map below, is practically in the center of the canyon, at its widest point.

The geology here hints at several Martian processes. The mesas and closed canyons in the north are typical of chaos terrain, where it erosion appears to form along fault lines to create the random intersecting canyons. In other places on Mars, in the mid-latitudes, that erosion appears mostly formed by glacial activity. Here, in Valles Marineris at only 7 degrees north latitude, little ice had been expected.

However, this spot is also in the dead center of a region where orbital data from Europe’s Trace Gas Orbiter (TGO) suggests there is a surprisingly large underground reservoir of hydrogen, which is assumed could only exist if it was locked in water molecules.

In fact, at this spot the data suggests up to 40% of the near-surface material might be composed of water (by weight). If so, that underground reservoir of ice could be causing the erosion that is creating this massive chaos terrain.

Meanwhile, the light-colored mountain in the south is the westernmost nose of a 50-mile-long ridgeline coming down from the canyon’s rim, about 30,000 feet higher. Its dendritic nature, like the hollows that form in the mountains of wet regions on Earth, suggest rainfall and water flowing downhill, wearing away these hollows over eons.

Rain however is almost certainly not the cause. Instead, we could be seeing erosion from wind, or maybe dry ice snow that fell long ago when this region was at a higher latitude when Mars’ rotational tilt was different.

Either way, the massive geology here illustrates the monumental nature of this largest canyon in the solar system, as well as the difficulties of exploring it.

The layered Martian history exposed in Valles Marineris

Overview map

The layers in Valles Marineris
Click for full image.

Cool image time! Like the Grand Canyon in the United States, Mars’ largest canyon, Valles Marineris, appears to have been carved out of a layered terrain, thus exposing those many layers in the walls of the canyon.

Valles Marineris, however, is much much larger than the Grand Canyon. You could fit dozens of Grand Canyons inside it and hardly fill it. Yet, its walls have the same layered look, suggesting that in Mars’ long geological history, first came many events that laid down new layers time after time, followed by a long period when the laying ceased and other events carved out the canyon to its almost 30,000 foot depth (which by the way is also about six times deeper than the Grand Canyon).

Today’s cool image to the right, cropped and reduced to post here, was taken on September 5, 2021 and shows a terraced terrain on the floor of Candor Chasma, one small side canyon of Valles Marineris that is still much larger than the Grand Canyon. The black dot in the overview map above indicates its location. I roughly estimate the elevation difference between the high and low spots in the picture is about 3,000 feet, a difference that while two-thirds that of the depth of the Grand Canyon is almost unnoticeable within the depths of Valles Marineris.

This layering is probably the canyon’s most important geological feature. See these previous cool images here and here for other examples. When geologists finally arrive on Mars and can begin dating these layers in detail they will likely reveal the planet’s entire geological history, going back five to six billion years.

Most of the layers are probably volcanic flood lava laid down by repeated eruptions from the giant volcanoes to the west. In between and within however will be deposits from the Martian atmosphere, telling us its composition and thickness. All told, the layers of Valles Marineris will likely unlock almost all of the most basic secrets of Martian geology.

We merely have to go there to find out.

The badlands on the floor of Valles Marineris

The badlands on the floor of Valles Marineris
Click for full image.

Cool image time! The recent discovery that there might be a near surface reservoir of ice on the floor the canyon Valles Marineris, near the Martian equator, immediately brought this location to the forefront as a possible site for establishing colonies. The weather will be less harsh than higher latitudes, the low elevation means a thicker atmosphere, and the terrain will be more appealing than the boring flat northern lowlands.

The picture to the right, cropped and reduced to post here, illustrates however the likely difficulties of landing and living on the floor of Valles Marineris. Taken on July 26, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), the photo shows just one small area of the floor of Ius Chasm, the western part of Valles Marineris and about 300 miles to the east of that water reserve.

In this one picture we can see trapped sand dunes in hollows, eroded depressions, mottled terrain resembling stucco, and innumerable cliffs and sinks and plateaus. For the first manned spacecraft to land on Mars, this is not a good first choice. Even later, when the first bases have been built, this terrain would still be forbidding for the early colonists to land in and traverse.

The overview map below shows exactly where this picture is relative to the rest of the Valles Marineris.
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Scientists discover underground reservoir of hydrogen, likely ice, near Martian equator

Detection of underground hydrogen in Valles Marineris
Click for full image.

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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A volcanic extrusion on the floor of Valles Marineris?

A volcanic extrusion on the floor of Valles Marineris?
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Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on August 31, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labels a “possible contact between two units.”

I think that contact is the point where that eroded mountain touches the surrounding smooth canyon floor. The mountain itself looks to me to be a very eroded extrusion of lava that was placed there from below a very very long time ago, covered later by material, and now exposed for a long enough period that its surface appears to have been carved by wind and even possibly flowing water or ice.

Because it is lava it is more resistant to erosion, which is why it sits higher than the smooth terrain around it. Even though both experienced the same processes of wear over time, the mountain’s surface was only carved away partly, while the material that had been in the floor was washed away entirely.

This is all a guess. However, a look below at the overview map, showing this mountain’s location on Mars, as well as MRO’s wider view from its context camera, I think strengthens my hypothesis.
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On the rim of Mars’ Grand Canyon

The rim of Valles Marineris
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Cool image time! Mars has many grand geological features that will surely attract tourists in the far future, when the planet has been successfully colonized and humans live there with the same ease that we today live in what was the New World wilderness several hundred years ago.

Of those features, none probably compare with Valles Marineris, the largest known canyon in the solar system. When compared to it, the Grand Canyon — at about a mile deep, about ten miles wide, and about 280 miles long — is a mere pothole, hardly noticeable. Valles Marineris averages a depth of five miles, a width of 370 miles, and a length of 1,900 miles. You could fit many Grand Canyons within it.

The photo to the right, cropped to post here, was taken on July 13, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows only a tiny section of this gigantic canyon’s rim. At this spot the depth from rim to floor is about 4.3 miles, or about 22,700 feet. In the image itself I estimate the cliff at the rim to be somewhere between 6,000 to 8,000 feet high, more than the depth of the entire Grand Canyon. And that’s only this top cliff.

The three overview maps below show the context of this location within Valles Marineris.
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Mars: On the floor of Valles Marineris

Strange flow (?) on floor of Valles Marineris
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Cool image time! The image to the right, rotated and cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on May 14, 2020, and shows a very strange bright outcrop on the floor of Valles Marineris, the largest canyon on both Mars and in the entire solar system.

MRO has photographed this spot a few times since 2007. The first image was posted with a detailed caption by Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona, who described the feature like so:

Most of the material is light and shows many small scarps or benches. In places these appear to indicate boundaries between layers, but they are often discontinuous. The light material is buried by a thin mantle of dark material in places; the dark material is from other rock layers—possibly those above the outcrop—and has fallen or been blown over the light rock.

Near the top of the outcrop, there is a distinctive layer that appears as a dark band at low resolution. At the full resolution of HiRISE, this appears to be a layer breaking up into angular boulders, indicating different rock properties than the underlying light rock. There does appear to be some light material above this layer, suggesting that the process that deposited the light material continued for some time.

Dundas also added that the lighter material is theorized to have “formed by a variety of processes. Proposed deposition mechanisms for light-toned sediments on Mars include those from rivers or lakes, volcanic ash or wind-blown sand or dust.”

Since this lighter colored outcrop has remained as bright as it has now for more than six Martian years, I doubt it is brighter because of the surface deposit of ash, sand, or dust (though it might be made of these materials which have now become hardened). My guess is that the brightness is inherent to the outcrop. Moreover, note the plateau to the southwest. Its rim is cut sharply, suggesting erosion revealed this outcrop, and that the outcrop is made of more resistant material.

The overview map provides some context that also might help explain the geology at this location.
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A deep dive into Valles Marineris

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

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

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

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

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

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

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

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

Valles Marineris

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

A closer view of the central regions of Valles Marineris

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

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

The exploration of the solar system has barely begun. Though we regularly get to see some spectacular images taken by the fleet of unmanned planetary probes that now circle or rove the various planets throughout the solar system, we mustn’t think we have seen very much. In truth, we have only gotten a very distant glimpse of only a few tiny spots, most of which have been viewed from very far away. Even at the highest resolution the images do not really tell us what it really will be like when we can stroll across those surfaces routinely.

To give you an idea of how much remains hidden, let’s take a journey inward from Mars orbit. The image below looks down on a good portion of the Martian globe, with the giant volcano Olympus Mons on the left, its three companion volcanoes in line to the east, and the vast valley of Valles Marineris east of these. This valley would cover the continental United States almost entirely, and extend significantly beyond into the oceans on either side.

Olympus Mons and Valles Marineris

This was essentially our first good look at Mars, taken from orbit by Mariner 9 in 1971.
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