The vast Martian plains of lava

The vast Martian lava fields
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on January 31, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Labeled “Lava Embaying Highlands Ridge”, it shows an alcove along a ridgeline that appears filled with material, in this case solid lava.

If you look closely at the ridgeline, you can see several dark streaks on its southern slopes. These streaks could be one of two unique Martian features that remain unexplained. They could be slope streaks, which occur randomly through the year and fade with time, or recurring slope lineae, which occur seasonally at the same locations. In either case, though the streaks look like avalanches, they don’t change the topography, have no debris piles at their base, and even sometimes flow uphill for short lengths. Though there are a number of theories for their formation, many involving dust, none has been accepted as confirmed.

This location and its lava however are the stars of this picture, for a number of reasons, all revealed by the overview map below.
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Mapping the layered geology of Mars

Mapping the layers on Mars
Click for original image.

Today’s cool image is an update of a previous cool image from July 2021. Then, I posted a captioned high resolution Mars Reconnaissance Orbiter (MRO) photo of the many terraced layers within a 13-mile-wide crater dubbed Jiji and located in Arabia Terra, the largest transition zone between the Red Planet’s northern lowland plains and the southern cratered highlands. At that time the caption noted that research was on-going to see if the same layers could be identified in two other nearby craters, Banes and Sera, and thus use that data to extrapolate the long term geological history of this region on Mars.

Today’s cool image to the right, rotated, cropped, reduced, and enhanced to post here, was taken on January 4, 2024 as part of this research, and shows the layers in 18-mile-wide Sera crater, located only about ten miles to the east of Jiji crater. The highest mesa near the bottom of the picture is about twenty feet high on its southern side, but about 140 feet high to the north. The difference is because the crater floor under the mesa is sloping downward to its lowest point to the north.
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Scientists: Mars’ mysterious slope streaks and seasonal recurring lineae are caused by dust

Massive flow on Mars
A typical Martian slope streak.

On Mars there are two mysterious features that are somewhat similar but entirely unique to the Red Planet, and for years have baffled planetary geologists as to their origins.

One feature is called slope streaks, which appear randomly year-round as either dark or bright streaks on slopes. They resemble avalanches, except that they do not change the topography, have no debris piles at their base, and sometimes travel along that topography, sometimes even going uphill for short distances. Over time these streaks then fade.

The other feature is called recurring slope lineae, because though they look like slope streaks, they are not random but appear seasonally at the same places each year. Lineae are also always dark.

Scientists have proposed many theories to explain both, with most theories involving some form of water process, either the seepage of brine from below or water vapor causing the Martian surface dust to flow, like droplets on a car windshield. None of these theories has been confirmed, or entirely accepted.

Two studies at this week’s 55th annual Lunar and Planetary Science Conference in Texas have both concluded that water is not a factor in the formation of either phenomenon. Instead, both papers propose a much simpler explanation: Wind and blowing dust interact to cause small dust avalanches.
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Lucy’s first encounter with an asteroid produced surprises

Dinkinesh, with Salam

At the 55th annual Lunar and Planetary Science Conference presently being held in Texas, the science team for the Lucy asteroid mission presented their first papers outlining what they learned during the spacecraft’s first asteroid encounter, flying past the main belt asteroid Dinkinesh on November 1, 2023.

To the right is the the best image taken at closest approach, at about 270 miles distance, annotated to include the analysis of Dinkinesh’s shape by scientists. As noted in the summary paper [pdf], the asteroid is about a half mile in diameter, and appears to have an equatorial ridge, similar to the ridges found on the near-Earth rubble-pile asteroids Bennu or Ryugu. Dinkinesh is not a rubble pile, however. Though boulder-strewn, it appears more solid, and even has what the scientists call a longitudinal trough, as indicated in the picture.

The ridge overlays the trough implying that it is the younger of the two structures. However, there is as yet no information to better constrain their relative ages, and thus they could potentially have formed in the same event. Indeed, Dinkinesh’s ridge and trough are likely the result of mass failure and the reaccretion of material, and may both be linked to the formation of Selam.

That flyby had produced one major surprise, the existence of a smaller satellite asteroid orbiting Dinkinesh, now dubbed Selam. It is shown in the lower left, as it appeared from behind the main asteroid as Lucy flew past. A later picture however revealed an even greater surprise.
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There likely is little or no ice in the Moon’s permanently shadowed craters

Shadowcam-LRO mosaic
The floor of Shackleton Crater showing no obvious ice deposits,
as seen by Shadowcam. The black cross marks the south pole.
Click for original image.

This week the 55th annual Lunar and Planetary Science Conference is being held in Texas. The conference was originally established in connection with the Apollo missions to allow scientists to release their Moon research results. It quickly morphed into an annual event covering research from the entire planetary research community.

I have reviewed the abstracts for this year’s meeting, and culled what I think are the most significant new results from the conference, which I will report on in the next few posts.

We begin however with possibly the most important result from the conference, given by the science team for the ShadowCam instrument on South Korea’s Danuri lunar orbiter. That low-light camera was designed to take high resolution pictures of the permanently-shadowed craters of the Moon, to see if there was any visible or obvious ice hidden there. Though the science team presented a number of papers, the summary paper [pdf] by the instrument’s principal investigator, Mark Robinson of Arizona State University, gave the bottom line:

The data so far is finding very little evidence of water ice in these dark regions.
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A Martian tadpole

Overview map

A Martian tadpole
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 28, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The white dot on the overview map above marks the location, with the rectangle in the inset marking the area covered by the picture. The science team labels this “inverted features,” a more vague way to describe the feature geologists dub “inverted channels.” The flow of a river or glacier acts to harden and increase the density of the channel bed. Later, the water or ice disappears, leaving just the canyon.

Even later, erosion begins to wear away the surrounding terrain. Because the canyon floor is now harder than that surrounding terrain, that floor is more resistent to erosion, and eventually becomes ridge following the exact same path as the long gone river or glacier.

This is what we have here, with this inverted channel, which is about five miles long, once draining into the deeper eroded valley to the south.

The location is at 38 degrees north latitude and inside the 2,000-mile-long mid-latitude region I dub glacier country, because almost every image shows evidence of glaciers or ice flows on the surface. This picture however is a rare exception. The features in this picture instead appear to be bedrock, something that is rarely seen in the canyons and craters in glacier country. It is beyond my pay grade however to explain why this spot lacks such features. Or it could be the near surface ice here looks so much like bedrock I am misinterpreting the picture.

The strange surface of the perennial dry ice cap at Mars’ south pole

The strange surface of Mars' dry ice cap
Click for original image.

Cool image time! The picture to the right, cropped to post here, was taken on January 24, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a region about 180 miles from the south pole of Mars.

This terrain is intriguing because is the pattern of ridges that cover it entirely. I have simply cropped the original image to show these ridges in highest resolution. The full image shows them covering a region much larger than this.

What are we looking at? Because it is near the pole, it is likely that the black splotches are caused by carbon dioxide gas breaking through the winter mantle of dry ice that covers the poles during the winter months and then sublimates away, from the bottom, each spring. As the dry ice turns to CO2 gas that gas is trapped, until it can find a weak spot in the overlying mantle. When the pressure builds enough, the mantle breaks, the gas escapes, and as it does so it deposits the dark dust around the breakage. That dust fades as the mantle disappears.

Sounds good, eh? Not so fast.
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The really really strange landscape of Cydonia on Mars

Some really strange terrain on Mars
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on January 3, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what the camera team describes merely as “landforms.”

In truth, these features, as well as almost everything in the surrounding terrain beyond the edge of this picture, are possibly the weirdest geological features on Mars. The two mounds, no more than fifteen feet high at the most, resemble pimples. The rough ground to the north actually appears to be some flow that worked its way around the mounds, as indicated by the arrows. The crack to the southeast of the two mounds appears to be an extension of a fault line that cuts through the center of the larger mound, suggesting the mound is some form of eruption belching out of that fissure.

That the latitude is 42 degrees north, these weird features all suggest some form of ice-based volcanic activity, because the ground here is probably impregnated with ice.

As for the bridge connecting the two mounds, who knows what caused it?
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A Martian cliff of ash, flushed by wind

A Martian cliff of ash flushed by wind
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 27, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). Described merely as an “exposed scarp” by the science team, this cliff edge is actually much more.

First some basic details. The elevation drop from the plateau down to the base of this cliff is about a thousand feet. The material that forms this plateau, scarp, and its base is all volcanic ash. The thicker sections of ash has caused its lower levels to compress, harden into a kind of sandstone. Near the surface however it is more friable, and like sandstone can break apart somewhat more easily.

The prevailing winds at this site are generally blowing to the south, but beginning to turn to the east, which explains the northwest to southeast orientation of the features.

The best analogy I can come up with to explain the erosion of this scarp is as follows: Imagine a deposit of dry mud a few inches thick on pavement. Take a leaf blower and blow at it hard, always in one direction. Eventually the outer edge will break up and blow away, leaving a sharp edge, that will also retreat with time as the wind continues to blow.

Here the winds are eroding that cliff, causing periodic avalanches which dissolve into sand that then blows away, leaving no debris pile at the base of the cliff. The ridges indicate harder material, that breaks away last, which is why there are some ridgelines extending outward from the scarp in line with these ridges. At the same time, these ridges of harder ash still break up with time, as some are cut off suddenly at the cliff edge.
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A recent volcanic eruption on Mars?

A recent volcanic eruption on Mars?
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on December 16, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labels the two darkened patches in the picture “plume-like features,” suggesting that the dark material was eruptive material thrown out from the depressions in a volcanic venting, that then settled on the nearby surrounding terrain.

Is that a correct interpretation? It is certainly strengthened by a different feature located about 550 miles to the northwest that looks almost the same. There, researchers theorize that the dark material surrounding a surface fissure was caused by a small volcanic event that occurred somewhere between 50,000 to 210,000 years ago. For that other location, scientists concluded as follows:

After careful comparison of this symmetrical dark feature with other dark wind-caused streaks in this region, the scientists concluded that it was not caused by wind, but is the remains of a relatively recent volcanic eruption that laid down a thin layer of material only about one foot thick.

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LRO locates and photographs Odysseus on lunar surface

Overview map
Click for original LRO image of Odysseus

Scientists using Lunar Reconnaissance Orbiter (LRO) this weekend located and photographed Intuitive Machines’ Odysseus Nova-C lunar lander at a height of 56 miles during its first orbit over the site.

The inset in the map to the right shows the lander, with the white dot marking its landing site, several miles to the south of the planned landing site, as indicated by the yellow dot.

Odysseus came to rest at 80.13 degrees south latitude, 1.44 degrees east longitude, 8,461 feet (2,579 meters) elevation, within a degraded one-kilometer diameter crater where the local terrain is sloped at 12 degrees.

That slope could by itself explain why the lander tipped over and ended up on its side. First, it landed faster than planned. Second, Intuitive Machines designed this Nova-C lander with a relatively tall configuration, which gives it a high center of gravity. Hitting the ground fast and on such a slope could easily have been enough for momentum to tilt it over after touchdown.

Mars’ flaky rocks

Mars' flaky rocks
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on February 21, 2024 by the high resolution camera on the Mars rover Curiosity. It once again shows us a very typical many layered rock that the rover has seen routinely in Gale Crater and in the foothills of Mount Sharp.

The long flake tells us many things. First, Mars’ one-third Earth gravity, thin atmosphere, and lack of life allows such flakes to survive. On Earth not only would wind and rain break such delicate forms, plant life would eat away at it as well.

Second, the many thin layers tell us again that Mars’ geological history comprises many cycles and geological events, each of which placed another layer down. The many layers here could actually be evidence of year-by-year events, much like tree-rings detail the drought conditions yearly on Earth.

It will take study on Mars however to find out. These image only tantalize. They cannot give answers.

Frozen lava rapids on Mars

Frozen lava rapids on Mars
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on October 6, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows a spot on Mars where lava was squeezed between and around some small peaks as it flowed quickly south, flooding all the low areas in this landscape.

The science team describes the features in the full image as “streamlined”, a description that is literally accurate. As this “stream” of lava rushed past, it “lined” the higher terrain, carving it into tear-dropped shapes.

In the color strip, note the blueish spots at the northern base of the 400-foot-high hill. According to the science team’s explanation [pdf] of the colors in MRO images, “Frost and ice are also relatively blue, but bright, and often concentrated at the poles or on pole-facing slopes.” The picture was taken in summer, so if these bright spots are frost or ice, it suggests they are well shaded from sunlight in those north-facing alcoves. This location is only 9 degrees north of the equator, so finding any near surface ice here is highly unlikely. That frost might exist however is intriguing, to say the least.
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Curiosity’s view of Gale Crater from its new heights on Mount Sharp

Low resolution version of panorama
Click for full resolution version of panorama. For the original images, go here, here, and here.

Overview map

Cool image time! The panorama above was created from three pictures taken on Februay 13, 2024 by the left navigation camera on the Mars rover Curiosity (available here, here, and here). It looks to the north, across Gale Crater and its nearest rim, about twenty miles away. The red dotted line indicates the approximate route Curiosity took to get to this point. The yellow lines on the overview map to the right show the approximate area covered by the panorama.

The images were part of the routine mosaics created by both the left and right navigation cameras for helping engineers plot the rover’s future travels. The pictures that look back at the far rim however also provide important atmospheric data. In this case, the haze tells the scientists how much dust is in the atmosphere. It is presently winter in Gale Crater, which also corresponds to the dust storm season. Thus, the view is very hazy.

Curiosity will likely remain at this location for several more weeks, as the science team is about to begin another drilling campaign. Note the large dark area on the cliff face on the right that is also level with the terrace where Curiosity presently sits. The scientists want to get core data of this layer, and they think they are at a good spot to do so.

Martian gullies caused by glacial and water erosion

A gully on the north rim of Niquero Crater
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on December 23, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The image shows us the north interior rim of 7-mile-wide Niquero Crater on Mars. From the high to the low points the elevation difference is about 2,500 feet, with a steep downhill slope averaging about 18 degrees. The terrain appears to show several avalanche collapses that pushed lower material out of the way, though at the bottom where that material has been pushed aside there is no obvious large debris pile.

The science team labels this image simply “volatiles and gullies”, a label that carries a host of significant information. These gullies, which were among the earliest found by Mars Global Surveyor in the late 1990s, were the first evidence that the surface of Mars had a lot of near surface ice. It is for this reason that this relatively small crater on Mars has a name. Most craters this small remain unnamed, but the gullies on Niquero’s north slopes required more study, and thus the crater was given a name.

Subsequent orbital imagery has now shown that craters like Niquero, located in latitudes higher than 30 degrees, quite often are filled with glacial debris. In fact, the material that these avalanches pushed aside at the base of the slope is that glacial material, protected by a thin layer of dust and debris. The avalanche essentially disturbed that protected layer, and thus the debris pile (made up mostly of ice) sublimated away when warmed by sunlight. Thus. no big debris pile.

The gullies tend to be on the pole-facing slopes. Scientists believe they are the remnant evidence of ancient glaciers that grew on these slopes because they were protected from sunlight. In subsequent eons, when the climate on Mars changed, those glaciers collapsed, leaving behind the gullies we see now.
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Alternating dark and light terraces inside Valles Marineris

Overview map

Alternating dark and light layered terraces in Valles Marineris
Click for original image.

Cool image time! The picture to the right, cropped and enhanced to post here, was taken on October 9, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what appear to be the somewhat typical terrain at this location, in a part of the giant Martian canyon Valles Marineris dubbed West Candor Chasma. For example, I featured similar swirls in August 2022 at a place only about six miles to the east, that spot indicated by the green dot on the overview map above. The white dot marks the location of today’s image.

So, what are we looking at? The elevation drop from the high and low points is only about 180 feet, but in that short distance it appears there are more than two dozen visible layers, and those layers form terraces that alternate between bright and dark material.

The shape of the swirls also suggest that a flow of some kind, either water, ice, or wind, moved from the northwest to the southeast, carving these terraces as it descended the stair steps downward. It is also just as likely that we are seeing repeated lava flows going downhill to the southeast, each even laying another layer on top of the preceeding one. And it is also possible that we are looking at a combination of both.

The alternating dark and light layers suggest that each dark layer was an event that put down dark material, such as volcanic dust, that was subsequently covered with light material, with this process repeating itself many times over the eons.

That the floor of this part of Valles Marineris is uniquely covered in this manner is in itself intriguing. Why here, and not elsewhere within the canyon?

The alien surface of Mars

The alien surface of Gediz Vallis
Click for original image.

Overview map
Click for interactive map.

Cool image time! The picture above, brightened slightly to post here, was taken on February 15, 2024 by the right navigation camera on the Mars rover Curiosity. It looks east at the looming cliff face of the mountain Kukenan that the rover has been traveling beside for the last six months. On the overview map to the right the yellow lines indicate roughly the area covered by this picture. The blue dot marks Curiosity’s present position, while the green dot marks its position on February 5, 2024. As you can see, the rover is making slow but steady progress uphill into Gediz Vallis.

This image illustrates the alien landscape of Mars quite beautifully. First, there is absolutely no life in this picture. On Earth you would be hard pressed to find any spot on the surface that doesn’t have at least some plant life.

Second, there is the rocky layered nature of this mountain. When the Curiosity science team first announced its future route plans (the red dotted line) to drive into this canyon back in 2019, the orbital images of these layers from Mars Reconnaissance Orbiter (MRO) had suggested the terrain here would be reminiscent of The Wave in northern Arizona, a smooth series of curved layers smoothed nicely over time by the wind.

As you can see, there is no smoothness here. Instead, every single layer here is infused with broken rock, suggesting that each layer is structurally weak. As erosion exposes each, the layer breaks up, crumbling into the chaos in this picture. The curved nature of the terrain at the bottom of the picture however does suggest that some sort of flow once percolated down this canyon, either liquid water or glacial ice, carving the layers into this curved floor.

The shoreline of a Martian lava sea

The shoreline of a Martian lava sea
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and enhanced to post here, was taken on October 2, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labeled this a “lava margin.” The darker material on the right is apparently a newer deposit of lava, flowing on top of the lighter lava on the left. The newer deposit is only about three feet thick, so it had to have flowed fast almost like water to cover this large area with such a thin layer before freezing. Even so, this new lava layer has a roughness greater than the older layer below it. Either the older layer is smoother because of erosion from wind over eons, or the lava in these two layers was comprised of slightly different materials that froze with different textures.

The small ridges appear to be wrinkle ridges, created when material shrinks as it freezes.

This margin marks the edge of a very large flood lava event, as illustrated by the overview map below.
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OSIRIS-REx brought home twice as much material from Bennu than planned

The inside of OSIRIS-REx's sample return capsule
The material found inside the sample return
capsule. Click for original image.

Curators cataloging the material returned by OSIRIS-REx’s sample capsule from the asteroid Bennu have now completed weighing the material,l and have discovered that the spacecraft grabbed more than twice as much material from Bennu as planned.

NASA’s OSIRIS-REx spacecraft delivered 4.29 ounces (121.6 grams) of material from asteroid Bennu when it returned to Earth on Sep. 24, 2023; the largest asteroid sample ever collected in space and over twice the mission’s requirement. The mission team needed at least 60 grams of material to meet the mission’s science goals, an amount that had already been exceeded before the Touch-and-Go Sample Acquisition Mechanism (TAGSAM) head was completely opened.

More than 60 grams were recovered outside the capsule that had stuck to it during touch-and-go operations. Once they were able to open the capsule and weigh the material inside, they found it had captured as much stuff, so that in total the mission brought back a double complement of material.

This material will now be distributed to scientists worldwide for study. It is likely that it will overturn almost all assumptions presently held about the make-up of the solar system’s asteroid population, since previous to the recent asteroid sample return missions of OSIRIS-REx and Japan’s Hayabusa-2 our only samples came from material that survived after burning through the Earth’s atmosphere. That journey resulted in an incomplete and biased census, with the most delicate material destroyed.

Spiders on the rim of a Martian crater

Spiders on the rim of a Martian crater
Click for original image.

Cool image time! The picture to the right, cropped to post here, was taken on December 29, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows strange spidery formations on the rim of a 17-mile-wide crater about 500 miles from the south pole of Mars.

Scientists think these spider features are formed due to the seasonal cycle on Mars. In the winter at the poles the carbon dioxide in the atmosphere falls as snow in the polar regions, creating a thin dry ice mantle that covers everything. When spring arrives, sunlight goes through the clear mantle to heat its base, causing that dry ice to sublimate into gas that is trapped below the mantle. Eventually that mantle cracks at a weak point and the gas escapes, spewing dark dust on its top. By summer the mantle is entirely gone, and the black splotches disappear as they blend back into the same colored ground.

At the south pole the ground appears to be firmer and more structurally sound than at the north pole. The trapped gas appears to travel upward along the same tributary paths to the same escape points each year, thus carving these spidery features that are permanent features.
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One instrument on Perseverance has a problem

One of the instruments on the Mars rover Perseverance appears to have a problem that is preventing it from using its laser to collect spectroscopic data of the nearby Martian surface.

Data and imagery from NASA’s Perseverance Mars rover indicate one of two covers that keep dust from accumulating on the optics of the SHERLOC instrument remains partially open. In this position, the cover interferes with science data collection operations. Mounted on the rover’s robotic arm, SHERLOC uses cameras, a spectrometer, and a laser to search for organic compounds and minerals that have been altered in watery environments and may be signs of past microbial life.

The mission determined on Jan. 6 that the cover was oriented in such a position that some of its operation modes could not successfully operate. An engineering team has been investigating to determine the root cause and possible solutions. Recently, the cover partially opened. To better understand the behavior of the cover’s motor, the team has been sending commands to the instrument that alter the amount of power being fed to it.

Should this troubleshooting fail to fix the dust cover, the rover’s other instruments can still compensate, gathering spectroscopy in other ways. Losing SHERLOC however will still reduce the data that Perseverance can obtain.

German-built mini-rover for Japanese Phobos mission shipped to Japan

A German-built mini-rover, dubbed Idefix, has now been shipped to Japan to intergrate it as a secondary payload on that country’s MMX mission to the Martian moon Phobos.

The rover itself weighs 25 kilograms (55 pounds), is 51 centimeters long (20 inches), and is designed to explore up to 100 meters of Phobos’ surface. During one of MMX’s closest approaches to Phobos, the rover will be released at an altitude between 40 and 100 meters above the surface and touch down on Phobos. The drop utilizes the low gravity of Phobos, which will allow IDEFIX to just fall onto the surface, roll, and then raise itself to prepare for the roughly three-month-long mission. The gravity of Phobos is only roughly 1/1000th of the gravity of Earth, which can be attributed to the moon’s small size. Phobos only has a diameter of approximately 27 kilometers.

“Thanks to the low gravity, IDEFIX will need between 60 to 80 seconds from release to the touchdown on Phobos. The impact will be with less than one meter per second,” explained Professor Markus Grebenstein, who is DLR’s project lead for IDEFIX, in an interview with NSF.

If all goes right, the rover’s mission will last at least 100 days. MMX itself it scheduled to reach Phobos in 2029.

Meanwhile, scientists used one of the Perseverance’s high resolution cameras to capture another partial eclipse of the Sun by Phobos. This is not the first such Phobos eclipse that Perseverance has photographed (see for example here and here), but it is neat nonetheless.

Martian dunes with strange splotches

Martian dunes with splotches

Cool image time! The picture to the right, cropped to post here, was taken on December 20, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labels as “Dunes with Blotches.”

The blotches, or as I call them splotches, are the round dark patches on dunes themselves. Though their darkness is reminiscent of the dark patches that appear as spider features in the south polar regions of Mars, there are problems linking the two. The spiders form when the winter mantle of dry ice that falls as snow begins to weaken when the Sun reappears in the spring. Sunlight travels through the clear dry ice to warm the base of the mantle, causing it to sublimate into carbon dioxide gas. That gas however is trapped at the base, and only escapes when the thin mantle cracks at weak points. As the gas puffs out it carries with it dust, which leaves dark patches on the surface that disappear when the mantle disappears entirely by summer.

In the southern hemisphere at the poles the ground is somewhat stable, so the trapped gas appears to travel along the same paths each year to the same weak spots. This in turn causes it to carve spidery patterns in the ground, like river tributaries, except here the tributaries of gas flow uphill to their escape point. At the north pole the ground is not as stable. Instead we have many dunes, so that the dry ice mantle sublimates away at different places each year. There is no chance to form such spider patterns over time.

Making these splotches more puzzling is the season. This picture was taken in the winter, at a time one would think no dry ice is sublimating away.
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More hiking possibilities on Mars!

More hiking possibilities on Mars
Click for original image.

Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 27, 2023 by the high resolution camera on Mars Reconniassance Orbiter (MRO). Dubbed a “terrain sample” by the science team, this picture was likely chosen not as part of any specific research project but to fill a gap in the camera schedule so as to maintain that camera’s proper temperature.

When the team needs to do this they try to pick interesting targets. In this case the location is the region of many many parallel north-south fissures that extend for more than 800 miles south of the giant but relative flat shield volcano Alba Mons. These fissures are grabens, cracks formed when underground pressure pushed the ground up and caused it to spread and crack.

What attracted me to this picture is the ridgeline. It struck me as a wonderful place to hike. I have even indicated in red the likely route any trail-maker would pick to go from the valley below up onto the ridge, and then along its knifelike edge to the south. The height of the cliff down to the east valley averages about six hundred feet, guaranteeing beautiful scenery the entire length.
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A small Martian volcano?

A small Martian volcano?
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on December 21, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labeled it a “fresh crater”, but that description I think is misleading, as it implies a recent impact.

The crater does not look like a fresh impact crater to me. Such things on Mars usually appear very dark, as the impact dredges up dark material. This crater is not dark. More significant is the crater itself. The small 300-foot-wide inner crater, surrounded by a circular plateau and all sitting inside the larger 1,200-foot-wide crater is completely unique compared to any impact crater I have ever seen. Impacts in soft material, such as ice-impregnated ground, can cause concentric ripple rings, but they don’t look like this.

Instead, this crater more resembles the caldera of a volcano, where subsequent eruptions can produce overlapping depressions at the volcano peak. (See for example this picture of Olympus Mons.)

Moreover, the crater sits on top of a peak approximately 300 feet high. While impacts in ice-impregnated ground on Mars can produce splash aprons as seen here, the crater usually sits at about the same elevation as the surrounding terrain, not at the top of a peak. This peak suggests the apron was forned not by a splash but repeated flows coming down from the top.
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Curiosity’s damaged wheels continue to appear stable despite the rough Martian terrain

A new look at Curiosity's worst wheel
To see the original images, go here and here.

The rover Curiosity on Mars has for more than two years been traveling across a very rocky and rough terrain as it climbs higher and higher on Mount Sharp inside Gale Crater. Since the rover’s wheels experienced far more damage than expected early in its mission, when it was on the floor of the crater where the terrain was not as severe, engineers have adopted a whole range of techniques to try to reduce any further damage.

First, they increased the safety margins on the software that guides Curiosity. It picks its way very carefully through the rocks, and stops immediately if it finds itself crossing terrain that is too rough.

Second, the science team does a photo survey of the wheels after every kilometer of travel. The two pictures to the right compare the damage on the rover’s most damaged wheel, with an image from the previous survey on top and the most recent image, taken yesterday, on the bottom. I have numbered the same treads, called grousers, in the two images to make it easier to compare them.

As you can see, it does not appear as if the damage has increased in the 210 sols or seven months of travel since the last survey. This wheel looks bad, but it is the worst wheel on the rover, and the strategies that the engineering team adopted years ago to reduce further damage continue to work, even as Curiosity traverses some very rough ground.

The software requires the rover to travel shorter distances in each drive when the ground is this rough, but the consequence is that it will last much longer, and thus have a better chance of reaching higher elevations on Mount Sharp.

Perseverance snaps its first picture of grounded Ingenuity

Overview map
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Ingenuity on dune, as seen by Perseverance on February 4, 2024
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Perseverance on February 4, 2024 finally moved into a position where it was close enough to take its first picture of the now grounded Ingenuity helicopter. That picture, cropped, reduced, and enhanced to post here, is to the right, taken by the rover’s left high resolution camera. You can see Ingenuity sitting on the slope of a dune near the upper right.

The overview map above provides the context. The green dot marks Ingenuity’s final resting spot. The blue dot marks Perseverance’s present location, with the yellow lines indicating approximately the area covered by the photo.

Whether the rover is now close enough to get good imagery for a final engineering test of Ingenuity — where its rotors will be rotated and shifted slowly to determine the extent of the propeller damage — is not clear. Perseverance could move much closer, but its science team might not want to cross these dunes out of fear the rover would get stuck. They might move forward a few more feet, to the top of the south bank of Neretva Vallis, before doing that test.

Juno completes its closest approach of the Jupiter moon Io

Io on February 3, 2024
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The Jupiter orbiter Juno successfully completed its 58th close fly-by of the gas giant, during which it also made its closest approach to the volcanic moon Io, zipping past at a distance of 932 miles. The image of Io to the right, cropped and reduced to post here, was taken at that closest Io approach, and shows a mountain on the horizon as well as a large shield volcano in the center (the dark splotch), with a major lava flow to the south. The picture was processed by citizen scientist Brian Swift.

Another image, processed by Björn Jónsson, shows the differences at one volcano dubbed Loki between the December 30, 2023 and the February 3, 2024 flybys. It appears that the brightness of the apron of lava that surrounds the volcano changes significantly depending on the lighting and the angle of view. In December it was almost black. In February it was greyish silver, almost shiny.

Another image, processed by Andrea Luck, captured faint eruption plumes on Io’s edge, caused by an ongoing eruption just beyond the horizon.

Juno still has four more flybys of Io coming up, but none will be as close as the February 3rd approach.

A spot where the surface of Mars cracked

The spot where Mars cracked
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 14, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small section of the Cerberus Fossae cracks, a parallel series of cracks that stretch more than 700 miles across the volcanic plains of Mars.

These cracks formed when the ground spread apart, creating a void in which the surface collapsed. You can see this process illustrated quite clearly by the crater in the lower right, as indicated by the arrow. The crater had existed prior to the crack. When the ground split and collapsed, only the northeast quadrant of the crater was destroyed.

These cracks might also have been the source of Mars’ most recent large volcanic event, as shown by the overview map below.
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Curiosity looks ahead at very rough terrain higher on Mount Sharp

Panorama on Sol 4086, February 3, 2024
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The rough terrain higher on Mount Sharp
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Cool image time! The picture to the right, reduced and enhanced to post here, was taken on February 3, 2024 by the high resolution camera on the Mars rover Curiosity. The area it covers is indicated by the rectangle on the panorama above, which has been cropped, reduced, and enhanced to post here. That panorama was created from 46 photos taken by the rover’s right navigation camera on that same day.

Those rough small peaks are higher on Mount Sharp, though far below its summit. The summit itself is not visible, and in fact has never been visible to Curiosity since it landed on Mars in August 2012. The peak is about 26 miles to the south and about 16,000 feet higher up, with much of the mountain in the way.

These small, rough peaks are in an area that the rover will likely never go, as shown in the overview map below.
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