Finding Martian glaciers from orbit

Glacier flow on Mars
Click for full image.

Today’s cool image is a great example of the surprises one can find by exploring the archive of the high resolution pictures that Mars Reconnaissance Orbiter (MRO) has produced since it arrived in Mars orbit back in 2006. The picture to the right, rotated, cropped, and reduced to post here, was taken by MRO’s high resolution camera back on May 4, 2017. I only found it because I had picked out a October 24, 2022 high resolution image that covered a different area of this same flow feature just to the north east. In trying to understand that 2022 picture I dug to see other images had been taken around it, and found the earlier 2017 photo that was even more interesting.

Neither however really covered the entire feature, making it difficult to understand its full nature. I therefore searched the archive of MRO’s context camera, which has imaged the entire planet with less resolution but covering a much wider area per picture. The context camera picture below captures the full nature of this feature.
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Cones, mounds, and layers of Martian ice?

Cones, mounds, and layers of Martian ice?
Click for full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on September 10, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The location is at 38 degrees north latitude, in the Martian northern lowland plains. At this latitude in these plains the geological features seen in high resolution pictures almost always invoke near surface ice, including processes that disturb that underground ice layer.

This picture is no different. Not only does it appear that a glacier is flowing down from the top of east-west ridge, the middle mound includes a crater with its southeast rim gone and appears filled with material that suggests ice.

The greater geographic context of this location can be seen in the overview map below.
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Crater at the edge of the Martian south pole ice cap

Oblique view of south pole crater
Click for full image.

Overview map

Cool image time! The oblique panorama above, reduced and sharpened to post here, was created from an image taken on May 19, 2022 by the European orbiter Mars Express. Its location on edge of the layered deposits of ice and dust that form most of the Martian southern ice cap is indicated by the white rectangle on the overview map to the right. From the press release:

While it may look like a winter wonderland, it was southern hemisphere spring at the time and ice was starting to retreat. Dark dunes are peeking through the frost and elevated terrain appears ice-free.

Two large impact craters draw the eye, their interiors striped with alternating layers of water-ice and fine sediments. These ‘polar layered deposits’ are also exposed in exquisite detail in the rusty red ridge that connects the two craters.

The scattered white patches are either water frost, or the winter mantle of dry ice, both now sublimating away with the coming of spring.

The black line on the overview map indicates the extent of the layered deposits, and suggest that the ridgeline is not considered part of that ice cap layer, in contradiction to the press release language above.

Which is it? I would guess the answer is simply the uncertainty of science. Some scientists took a look here and decided the ridge was actually a base layer sticking up through the layered deposits. The European scientists who took this picture have instead concluded, based on the image, that the ridge is part of the layer deposits.

Perseverance experiment generates new record of breathable oxygen on Mars

MOXIE, an experiment on the rover Perseverance to see if breathable oxygen could be generated from the carbon dioxide in the Martian atmosphere, has set a new production record.

The atmosphere around Jezero Crater, the present location of Perseverance, reached peak density for the year mid (Earth) summer. This presented the perfect opportunity for the MOXIE science team to step on the accelerator and test how fast we could safely produce oxygen. This test occurred on Sol 534 (Aug. 22, 2022) and produced a peak of 10.44 grams per hour of oxygen. This represented a new record for Martian oxygen production! The team was thrilled to surpass our design goal of 6 grams per hour by over 4.4 grams. The peak rate was held for 1 minute of the 70 minutes oxygen was produced during the run.

MOXIE’s next opportunity to operate came recently. Despite the decreasing density of the Mars atmosphere, on Sol 630 (Nov. 28, 2022) MOXIE managed to break the record again and produce nearly 10.56 grams per hour at peak. Oxygen production was sustained for a 9.79 grams per hour for nearly 40 minutes.

These numbers may seem small, but MOXIE production runs are limited by available rover power. In addition, MOXIE technology was miniaturized to accommodate the limited space available on the rover. A MOXIE for a human Mars mission would produce oxygen nearly 200 times faster and work continuously for well over a year.

Ten grams per hour is about half what one person needs to breathe, and is a little less than a large tree produces. Moreover, MOXIE had earlier conducted seven other runs, producing about six grams of oxygen per hour during each.

Based on these tests, MOXIE has unequivocally proven that future human explorers will not need to bring much oxygen with them, and will in fact have essentially an unlimited supply, on hand from the red planet itself. More important, MOXIE has also proven that the technology to obtain this oxygen already exists.

All we need to do is plant enough MOXIE trees on Mars.

Bursting lava bubbles on Mars

Burst lava bubbles on Mars
Click for full image.

Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 4, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

I really have no idea what caused these distorted cones. My intuition (a dangerous thing to rely on when it comes to science) suggests these are volcanic in nature. Imagine hot lava with gas bubbling up from below. Periodically a gas bubble will burst on the surface releasing the gas. Depending on temperature, that bursting bubble could harden in place.

The overview map below provides some support for my intuition, but it also suggests this first hypothesis could be completely wrong, something that does not surprise me in the least.
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Perseverance deposits first core sample for pickup later

Perseverance's location December 21, 2022
Click for interactive map.

The Mars Perseverance rover has now deposited its first core sample on the floor of Jezero Crater for pickup later by a future Mars helicopter for eventual return to Earth.

A titanium tube containing a rock sample is resting on the Red Planet’s surface after being placed there on Dec. 21 by NASA’s Perseverance Mars rover. Over the next two months, the rover will deposit a total of 10 tubes at the location, called “Three Forks,” building humanity’s first sample depot on another planet. The depot marks a historic early step in the Mars Sample Return campaign.

The blue dot on the map to the right shows this location. The green dot shows Ingenuity’s present position. The red dotted line the rover’s future travel route.

InSight mission ended

Location of InSight's largest quakes
The white patches mark the locations on Mars of the largest quakes
detected by InSight

NASA today announced that it has officially ended the mission of the InSight lander on Mars.

Mission controllers at the agency’s Jet Propulsion Laboratory (JPL) in Southern California were unable to contact the lander after two consecutive attempts, leading them to conclude the spacecraft’s solar-powered batteries have run out of energy – a state engineers refer to as “dead bus.”

NASA had previously decided to declare the mission over if the lander missed two communication attempts. The agency will continue to listen for a signal from the lander, just in case, but hearing from it at this point is considered unlikely. The last time InSight communicated with Earth was Dec. 15.

Other than the success of InSight’s seismometer, this project was mostly a failure. Its launch was delayed two years, from 2016 to 2018, because of problems with the original French seismometer, forcing JPL to take over. Then its German-made mole digger failed to drill into the Martian surface, causing the failure of the lander’s second instrument, a heat sensor designed to measure the interior temperature of Mars.

Fortunately the seismometer worked, or otherwise it would have been a total loss. That data has told us much about Mars and its interior.

A congregation of Martian dust devils

A congregation of Martian dust devils
Click for full image.

Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 9, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a spot on Mars where, as indicated by the many many tracks, dust devils routinely develop and travel across the surface.

Though this whole region appears to favor dust devils, within it are places that are even more favored. For example, the number of tracks on the northern and eastern slopes of that small hill at center left practically cover the surface, while the hill’s western and southern slopes are almost untouched.

Both the overview map and the global Mars map below provide the full context.
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Perseverance’s planned route up onto the Jezero Crater delta

Perseverance's future route onto the delta
Click for original image.

Even as the Perseverance science team prepares to cache the ten first core samples on the surface of Mars for later pickup by a future Mars helicopter for return to Earth, they have also released the planned route they intend to follow as they drive the rover up onto the delta that flowed into Jezero Crater in the distant past.

The black line on the map to the right shows that route, with the black dots indicating points in which further core samples will likely be taken. The red dot indicates Perseverance’s present position, with the white line indicating its past travels. The green dot marks Ingenuity’s present position.

InSight fails to respond during scheduled communications session

InSight's daily power levels as of December 12, 2022

Since December 15, 2022 engineers have been unable to contact the Mars InSight lander, which likely means its power levels have finally fallen so low that the spacecraft is no longer functioning.

On Dec. 18, 2022, NASA’s InSight did not respond to communications from Earth. The lander’s power has been declining for months, as expected, and it’s assumed InSight may have reached its end of operations. It’s unknown what prompted the change in its energy; the last time the mission contacted the spacecraft was on Dec. 15, 2022.

The graph to the right shows the decline in InSight’s power levels since May. The atmosphere has been clearing following the dust storm in October, indicated by the drop in the tau level. Normal tau levels outside of dust storm season are around 0.6-0.7. It is therefore likely that as this dust cleared, it also settled on InSight’s solar panels, and reduced their ability to generate power to the point the spacecraft ceased functioning.

This is very much the same thing that put the rover Opportunity out of business in 2019.

According to this update, engineers are going to continue to try to contact the lander, but it is likely that this effort will end in about a week, should no contact be successful.

Big sink near the Martian south pole

Big sink near the Martian south pole
Click for full image.

Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 12, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The image is rotated so that south is at the top. The science team labels this a “subsidence feature,” or in plain English, a sinkhole.

Its perfectly circular shape, plus its central peak, strongly suggests we are looking at an impact crater. However, the lack of a raised rim of debris, produced by the ejecta from the impact, raises questions about this conclusion, and is one reason why the scientists think this is a sinkhole instead. Its shape however could be telling us that this sink is simply mirroring the existence of a buried crater.

The overview map below as always provides more context.
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The edge of the Martian south pole ice cap

The edge of the Martian south pole ice cap
Click for full image.

Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 4, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The MRO science team labeled this simply “Diverse Terrain,” an apt description but woefully incomplete.

Though the grade here goes uphill to the south, there are ups and downs along the way. The flat areas near the top as well that band near the bottom appear to be the oldest terrain, with the rough hollows appearing to be places where that flat material has sublimated or eroded away.

This terrain is in the very high southern latitudes. South is to the bottom of this picture, with the south pole of Mars about 380 miles away. Thus, that eroding top layer is likely disappearing because it has either water ice or dry ice within it, and over time it sublimates away.

The picture itself was taken in winter, when the entire surface is likely covered with a thin mantle of dry ice that fell as snow with the coming of colder temperatures. A wider view of this region in the spring, taken by MRO’s context camera, shows that this mantle, now appearing like white frost, appears largely confined to the higher terrain. Apparently, the annual sublimation of this dry ice mantle is linked somehow to the erosion of this flat terrain.

The additional location information provided by overview map below helps explain why this terrain is so diverse.
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Ingenuity completes 36th flight; preps for its 37th

Overview map
Click for interactive map.

Ingenuity on December 10, 2022 successfully completed 36th flight, flying about 180 feet to the northwest and then returning the same distance to land at its take-off point.

This was the third flight in a row to land at this point, and was also the third flight since the Mars helicopter’s software was upgraded to allow it to fly higher and over rougher terrain.

The green dot on the map to the right shows Ingenuity’s present position. The blue dot shows where Perseverance presently sits. The rover has been moving eastward, away from the cliff face to the west where it had gathered more core samples, including the first to contain surface regolith (that is, the dirt of Mars).

Engineers are already planning Ingenuity’s 37th flight, which is scheduled for tomorrow and will reposition the helicopter to a new landing spot.

Sunken butte on Mars

Collapsed butte in the Martian northern lowland plains
Click for full image.

Cool image time! The photo to the right, cropped, reduced, and sharpened to post here, was taken on November 1, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label a “layered butte.” Like the mesas in the American southwest, those layers, or terraces, mark the geological history of this place, where over time layer upon layer was placed down, and then eroded away except for this mesa.

What makes the mesa even more intriguing and strange, however, are surrounding concentric cracks and the moat at the mesa’s base. These features suggest that at some point the ground below the mesa collapsed so that the entire mesa dropped, as a unit.

What could cause this? The overview map below provides a clue, though certainly not an answer.
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Perseverance records sound of dust devil

For the first time scientists have used the microphone on the Mars rover Perseverance to successfully record the sound of dust devil as it flowed overhead.

I have embedded a video of the recording below. The research paper can be read here.

Dust devils on Mars, while much less dense in its very thin atmosphere, are generally much larger than found on Earth.

The dust devil recently detected by Perseverance was 25 meters wide and 118 meters tall (82 feet by 387 feet), putting it squarely in the average zone in terms of size for Martian dust storms. But they can grow much bigger, too, as dust on Mars can be whipped up in huge global dust storms.

The data also picked up the sound of dust particles hitting the microphone, which will allow the scientists to measure the density of the devil.
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Scientists publish papers describing largest Mars quake from May

Location of May quake

Though news of the largest quake so far detected by InSight on Mars, magnitude 4.7, was released in May, this week the science team published two papers describing the quake itself and what they have learned from it. From the press release:

The waves from the record-breaking quake lasted about 10 hours — quite a while, considering no previous Marsquakes exceeded an hour.

It was also curious because the epicenter was close to but outside the Cerberus Fossae region, which is the most seismically active region on the Red Planet. The epicenter did not appear to be obviously related to known geologic features, although a deep epicenter could be related to hidden features lower in the crust.

Marsquakes are often divided into two different types — those with high-frequency waves characterized by rapid but shorter vibrations, and those of low-frequency, when the surface moves slowly but with larger amplitude. This recent seismic event is rare in that it exhibited characteristics of both high- and low-frequency quakes. Further research might reveal that previously recorded low- and high-frequency quakes are merely two aspects of the same thing, Kawamura said.

The green-dotted white patch on the map above marks the approximate location of this quake, east of where most of the previous larger quakes have been detected and under the Medusa Fossae Formation of volcanic ash. That no surface features appear to correspond to this quake, it is thought it was the result of a shift of underground features.

Curiosity looks down Gediz Vallis

Curiosity's looks down Gediz Vallis
Click for original image.

Overview map
Click for interactive map.

The panorama above was taken by Curiosity’s right navigation camera today, December 14, 2022, looking down into Gediz Vallis, the giant slot canyon that the rover will use as its route up Mount Sharp.

The red dotted lines above and on the overview map to the right indicate approximately the planned route for Curiosity. The yellow lines indicate the approximate area covered by the panorama above.

At present the scientists are attempting to drill into the marker band on which Curiosity sits. This marker layer is visible at many places at about the same elevation on all sides of Mount Sharp’s flanks. The white arrows indicate other examples of it in this overview map. It generally appears smooth and flat, which suggests it is made of a harder substance more resistant to erosion. That hardness was confirmed when Curiosity’s first drill attempt into it last week failed. The scientists are now trying again.

The featureless volcanic ash plains of Mars

The featureless volcanic ash plains of Mars

Cool image time! The photo to the right, cropped, reduced, and sharpened to post here, was taken on September 10, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what appears to be a relatively featureless plain with a surface resembling stucco.

At -9 degrees south latitude, this is in the Martian dry equatorial regions. No ice or glaciers here. However, the consistent orientation of the knobs and hills suggest dunes and sand blown by prevailing winds, and that guess holds some truth. This location is deep within the Medusae Fossae Formation, the largest volcanic ash deposit on Mars, covering an area about as big as India, and believed to be the source of most of the red planet’s dust.

We are thus looking at thick layer of ash, its surface shaped over eons by the winds of Mars’ thin atmosphere.
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InSight still going, but barely

InSight's daily power levels as of December 12, 2022

The InSight science team issued another update today, outlining the continuing low power levels produced by the Mars lander, barely enough to keep its seismometer, and nothing else, running.

As of Dec. 12, 2022, InSight is generating an average of ~285 watt-hours of energy per Martian day, or sol. The tau, or level of dust cover in the atmosphere, was estimated at .96 (typical tau levels outside of dust season range from 0.6-0.7).

I have added these numbers to the graph at right in order to show their context over time. Since the October dust storm the levels have held steady, even as the dust in the atmosphere has cleared somewhat.

Nonetheless, InSight’s future continues to be day-to-day. Should it fail to respond to two consecutive scheduled communications sessions, the team will declare it dead, and make no effort at recovery. Though they have been expecting this to happen since the end of October, the lander continues to hang on.

Strange terrain on the eastern floor of Gale Crater

Strange terrain on the eastern floor of Gale Crater
Click for full image. For the inset, go here.

Though today’s cool image on the right, rotated, cropped, and reduced to post here, shows a small section on the floor of 96-mile-wide Gale Crater where Curiosity has been roving for the past decade, this picture looks at a different place. Curiosity landed in the northwest quadrant of the crater, and has been climbing the western slopes of Mount Sharp, which fills much of the crater’s interior. Today’s image looks at the crater’s floor on the east side of Mount Sharp.

The picture was taken on September 30, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The dark areas are likely dune seas, while the golden section near the top of the color strip is likely dust, though that is not certain. (This bright yellow is unusual for this particular color filter.) The greenish color suggests coarser materials, such as larger boulders and rocks, though this is also not certain.

The inset zooms into some unusual polygon lines that cut across the dunes and cratered terrain. Such lines suggest that once, in the far past, the ground here was wet. When it dried out (being now in the very dry equatorial regions of Mars) it formed these cracks, similar in nature to the polygon cracks one sees in drying mud on Earth. Since the data from Curiosity when it was on the crater floor also suggests a lake once existed inside the crater, these cracks add weight to that conclusion.

The overview map below places Gale Crater in the larger context of Mars.
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Ancient lava flows down the flanks of the solar system’s largest volcano

Lava flows on Olympus Mons
Click for full image.

Cool image time! The photo to the right, cropped, reduced, and sharpened to post here, was taken on October 2, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what appears to be very old and eroded lava on the northeast flanks of Olympus Mons, the largest volcano on Mars as well as the entire solar system. About 600 miles across, from the edge to its peak, Olympus rises about 54,000 feet, with an actual height relative to Mars’ “sea level” of just under 70,000 feet, more than twice as high as Mount Everest on Earth.

The white arrow show the downward grade. Several different flows can be seen throughout the picture, some confined to a central channel with smooth aprons of overflows on either side. Others are more broken and less coherent, and suggest that either the flows were inherently different, or are much older and have deteriorated with time.
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What a Martian impact looks like on a sheet of slushy ice

Overview map

What a Martian impact looks like on a sheet of ice
Click for full image.

My headline is a bit of a guess, but it is an educated guess for today’s cool image. The photo to the right, cropped, reduced, and sharpened to post here, was taken on October 30, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The location, as indicated by the white dot in the overview map above, puts this impact in a relatively flat area of Deuteronilus Mensae, the westernmost chaos region of the 2,000 mile long mid-latitude strip I call glacier country.

In other words, there is likely a lot of near surface ice here, as this impact makes very plain. If you imagine dropping a pebble into a thick layer of soft ice cream, you might get a crater reminiscent of this. I use for comparison ice cream on Earth because the lighter Martian gravity probably makes Martian ice softer and more slushy.

As I have said many times before, Mars is strange, Mars is mysterious, and above all Mars is alien.

A Martian ship’s prow

A Martian ship's prow
Click for full image.

Cool image time! The photo to the right, cropped, reduced, and sharpened to post here, was taken on August 31, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists call “layering” surrounding this pointed mesa, which I roughly estimate to be somewhere between 200 to 400 feet high.

As you approach the mesa you first walk on the dust-covered flat plains. Then you start up a slope of what looks like alluvial fill, material that over time has fallen from the mesa to pile up as an apron at its base. You then reach a series of terraces, each likely marking a different layering major event from sometime in the distance past. Over time, for unknown reasons, the material surrounding this material has eroded away, while the mesa and its layers somehow survived.

The overview map below helps tell us what those past layering events were, as well as the source of the large amount of dust and sand at this location.
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Ingenuity sets altitude record on 35th flight

Overview map
Click for interactive map.

On December 3, 2022 Ingenuity completed its 35th flight, traveling about 49 feet sideways but reaching a new altitude record for the Mars helicopter of 46 feet.

The map to the right shows the helicopter’s new position by the green dot, with Perseverance’s present position shown with the blue dot. The helicopter only moved slightly to the northwest of its previous position.

The plan had been to test the helicopter’s upgraded software at this new altitude while flying fly 50 feet sideways for 52 seconds at a speed of 6.7 feet per second. The flight met these goals almost exactly, going a distance only slightly shorter, well within its margin of error. The new altitude record however is significant, as going even slight distances higher in Mars’ very thin atmosphere (1/1000th of Earth’s) is challenging, to say the least. This higher flight means Ingenuity can fly up above higher terrain, such as the delta that is Perseverance’s next goal.

InSight’s low power levels holding steady

InSight's power levels as of November 29, 2022

The science team for the Mars’ lander InSight today (December 6th) released a new update (dated November 29th) of the power levels being produced by its dust-covered solar panels.

As of Nov. 29, 2022, InSight is generating an average between 290 watt-hours of energy per Martian day, or sol. The tau, or level of dust cover in the atmosphere, was estimated at .95 (typical tau levels outside of dust season range from 0.6-0.7).

I have added this new data unto the graph to the right, though I am puzzled by the date given to the update. Why post this today, when this update covers data only two days after the previous update (November 27th), and is more than a week out of date? This is especially puzzling because the numbers did not change at all.

Nonetheless, the lander is still alive, but barely. One wonders however what happened in the past week, since today’s update does not bring us up to date.

Martian dunes, as far as the eye can see

Martian dunes
Click for full image.

Cool image time! The photo to the right, cropped, reduced, and sharpened to post here, was taken on July 14, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the dune filled floor of an unnamed 25-mile-wide ancient and very eroded Martian crater.

These endless dunes — which extend far beyond this photo to cover the entire floor of this crater as well as an overlapping crater to the north that is only slightly smaller — reveal something fundamental about this location: The winds prevail from one direction consistently, from either the north or the south. Closer inspection would likely resolve which way, but I don’t have the knowledge or access to the data to do so.

The overview map below, provides context, and also further information about why these dunes are here.
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Curiosity’s recent and future travels amid the Martian mountains

Curiosity's recent and future travels on Mars
Click for full panorama.

Overview map
Click for interactive map.

The panorama above, created from 31 images taken by Curiosity’s right navigation camera on December 5, 2022, provides us a wonderful overview of the rover’s recent and future travels amid the lower foothills of Mount Sharp in Gale Crater.

The overview map to the right provides context. The blue dot indicates Curiosity’s present position. The yellow lines indicate the approximate area viewed by the panorama. The red dotted line indicates Curiosity’s planned route, with the white dots the route it has actually traveled. On the panorama, the pink dotted line indicates where it has been, and the red dotted line where it is going.

For scale, Kukenan is estimated to be about 1,500 feet high. Though Chenapua in front seems comparable, it is actually much smaller, only about 200 to 300 feet high, at the most. Orinoco, though lower on the mountain, is probably about 300 to 400 feet high.

To really see the magnificence of this terrain, you must click on the panorama and explore the full image. Curiosity is truly traveling amid mountains, and is the first human robot to do so on another world.

Martian glaciers below 30 degrees latitude

A Martian glacier below 30 degrees north latitude
Click for full image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on September 28, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). While it shows what looks like a somewhat typical Martian glacial flow pushing through a gap between hills, this glacial flow is not typical. It sits at just under 30 degrees north latitude, closer to the equator than almost any glacial feature on Mars. Moreover, the younger impact crater on top suggests this glacier has been here for some time. Though the impact is younger than the crater, it is not that young, as the dark streaks normally seen in the first years after impact are gone.

Thus, this glacier suggests that not only can near surface Martian ice exist closer than 30 degrees latitude from the equator, it can survive there for a considerable amount of time.

Nor is this glacial flow, so close to the equator, unusual for this region of Mars.
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Expanded craters in Martian ice

Expanded craters in Martian ice
Click for full image.

Cool image time! The photo to the right, rotated, cropped, reduced, and sharpened to post here, was taken on August 18, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It includes a wide variety of geology related to sublimating ice, including expansion cracks as well as several different examples of what scientists call “expanded craters,” impacts that occurred in near surface ice and have been reshaped by the ice’s melting and sublimation at impact and then later. It also shows some obvious glacial fill in the two distorted craters at the center right.

A 2017 dissertation [pdf] by Donna Viola of the University of Arizona outlines nicely what we know of Martian expanded craters. As she notes in her conclusion:
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Scientists: Viking-1 might have landed on a field of Martian tsunami debris

The geological history of the Viking-1 Mars landing site

As outlined in their new paper [pdf], a team of scientists now hypothesize that the features that surrounded Viking-1 when it landed on Mars in 1976 were caused by two past Martian tsunamis. Each tsunamis occurred due to an impact in the theorized ocean that is believed to have existed in this part of Mars’ northern lowland plains several billion years ago.

The graphic to the right, figure 8 from the paper, shows the hypothesized sequence of events. From the caption:

(a) Pohl crater forms within a shallow marine environment, (b) triggering tsunami water and debris flow fronts. (c) The wave fronts extensively inundate the highland lowland boundary plains, including a section ~ 900 km southwest of the impact site. (d) The ocean regresses to ~ − 4100 m, accompanied by regional glacier dissection, which erode the rims of Pohl and other craters. (e) The younger tsunami overflows Pohl and parts of the older tsunami. Glaciation continues, and mud volcanoes later source and emerge from the younger tsunami deposit. (f) ~ 3.4 billion years later, the Viking 1 Lander touches down on the edge of the older tsunami deposit.

The overview map below provides the larger context.
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