Tag: Mars Reconnaissance Orbiter

Rover update: May 30, 2019

12:28 pm

Summary: Curiosity confirms clay in the clay unit. Yutu-2 begins its sixth day on the far side of the Moon. Three other rovers move towards completion and launch.

For the updates in 2018 go here. For a full list of updates before February 8, 2018, go here.

Clouds over Gale Crater
Clouds over Gale Crater

Curiosity

For the overall context of Curiosity’s travels, see my March 2016 post, Pinpointing Curiosity’s location in Gale Crater.

Curiosity’s journey up the slopes of Mount Sharp in Gale Crater goes on! On the right is one of a number taken by the rover in the past week, showing water clouds drifting over Gale Crater.

These are likely water-ice clouds about 19 miles (31 kilometers) above the surface. They are also “noctilucent” clouds, meaning they are so high that they are still illuminated by the Sun, even when it’s night at Mars’ surface. Scientists can watch when light leaves the clouds and use this information to infer their altitude.

While these clouds teach us something about Martian weather, the big rover news this week was that the data obtained from the two drill holes taken in April show that the clay formation that Curiosity is presently traversing is definitely made of clay, and in fact the clay there has the highest concentration yet found by the rover.

This clay-enriched region, located on the side of lower Mount Sharp, stood out to NASA orbiters before Curiosity landed in 2012. Clay often forms in water, which is essential for life; Curiosity is exploring Mount Sharp to see if it had the conditions to support life billions of years ago. The rover’s mineralogy instrument, called CheMin (Chemistry and Mineralogy), provided the first analyses of rock samples drilled in the clay-bearing unit. CheMin also found very little hematite, an iron oxide mineral that was abundant just to the north, on Vera Rubin Ridge. [emphasis mine]

That two geological units adjacent to each other are so different is significant for geologists, because the difference points to two very different geological histories. The formation process for both the clay unit and Vera Rubin Ridge must have occurred at different times under very different conditions. Figuring out how that happened will be difficult, but once done it will tell us much about both Gale Crater and Mars itself.

With the success of their clay unit drilling campaign, the Curiosity science team has had the rover begin its trek back from the base of the cliff below Vera Rubin Ridge to its planned travel route up the mountain.

An updated description of that route was released by the Curiosity science team last week, while I was in Wales. Below is their image showing that route, with additional annotations by me and reduced to post here.
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The mysterious slope streaks of Mars

12:10 pm

Massive flow on Mars
A typical Martian slope streak.

The uncertainty of science: In the past decade or so scientists have documented in detail a number of features on the Martian surface that evolve or change over time. From the constantly changing poles to the tracks of dust devils to landslides to the appearance of seasonal frost, we have learned that Mars is far from a dead world. Things are happening there, and while they are not happening as quickly or with as much energy as found on Earth, geological changes are still occurring with regular frequency, and in ways that we do not yet understand.

Of the known changing features on Mars, two are especially puzzling. These are the two types of changing streaks on the slopes of Martian cliffs, dubbed recurring slope lineae (referred as RSLs by scientists) and slope streaks.

Lineae are seasonal, first appearing during the Martian summer to grow hundreds of feet long, and then to fade away with the arrival of winter. Their seasonal nature and appearance with the coming of warm temperatures suggests that water plays a part in their initiation, either from a seep of briny water or an avalanche of dust. Or a combination of both. The data however does not entirely fit these theories, and in fact is downright contradictory. Some studies (such as this one and this one) say that the seasonal lineae are caused by water. Other studies (such as this one and this one) say little or no water is involved in their seasonal formation.

The answer remains elusive, and might only be answered, if at all, when Curiosity takes a close look at two lineae in the coming years.

Slope streaks however are the focus of this post, as they are even more puzzling, and appear to possibly represent a phenomenon entirely unique to Mars. I became especially motivated to write about these mysterious ever newly appearing features when, in reviewing the May image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO), I found four different uncaptioned images of slope streaks, all titled “Slope Stream Monitoring.” From this title it was clear that the MRO team was re-imaging each location to see if any change had occurred since an earlier image was taken. A quick look in the MRO archive found identical photographs for all four slope streak locations, taken from 2008 to 2012, and in all four cases, new streaks had appeared while older streaks had faded. You can see a side-by-side comparison of all four images below the fold.
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The floor of Marineris Valles

12:02 pm

Close-up of the floor of Marineris Valles

Larger view
Click for the full image.

To the right is small section cropped out of an image, taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on March 30, 2019, of one very tiny area of the floor of the 2,500 mile long Marineris Valles, the biggest known canyon in the solar system.

Below this on the right is a larger section of the full image, with the white box showing the part covered by the top photograph. The general flow direction is to the east.

The photograph, uncaptioned, is titled “Terminus of Pitted Materials Emanating from Oudemans Crater.” Oudemans Crater is about 55 miles across and is located near the head of Marineris Valles to the east of the giant volcanic region dubbed the Tharsis Bulge. The meteorite that caused this crater is estimated to have been a little less than 3 miles in diameter. It is believed by some scientists that the impact heated up subsurface carbon dioxide permafrost which then explosively flooded down the Valles Marineris into the Northern Plains of Mars, pushing a lot of pulverized debris in front of it..

Instead of liquid water, what is stored underground on Mars is liquid CO2 and when a collapse occurs, this boils almost instantly and explosively to CO2 vapour, blasting the rock and regolith to dust, except for the most resistant fragments such as igneous rocks. The rest of the regolith is composed of dust and gravel, weakly cemented by water ice. On Mars, water is not a fluid, but behaves as a mineral in most situations. Grains of ice would be tumbled along in the cryogenic flows, and transported as passive solids just like quartz grains are transported as sand by rivers on Earth.

This theory, if correct, would eliminate the need for liquid water on the surface, and would explain many of the planet’s geological surface features.

Overview

The overview thumbnail to the left shows the location of both Oudemans Crater and this MRO image, indicated by the very tiny blue rectangle near the thumbnail’s center..

The “pitted materials” in the image’s title refers to that flowing avalanche of pulverized ice, rock, and dust, shown in the picture by the curved terraced cliffs descending to the east. This is where this material settled as it flowed eastward, pushed by that explosive CO2 flood.

You can see another example of this eastward flow in another MRO image taken just to the west. The canyon floor is pitted, confused, and rough, but there is an obvious flow trend to the east.

In fact, much of the floor of Marineris Valles that has been photographed at high resolution is similarly rugged. It will be a challenge to explore this place, especially because we have only imaged a small percentage at high resolution. There is much there that remains unseen and unknown.

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Fractured and collapsed Martian crater floor

4:06 pm

Fractured and collapse Martian crater floor
Click for full image.

Time for some puzzling Martian geology. The image on the right, rotated, cropped, and reduced to post here, comes from the Mars Reconnaissance Orbiter (MRO) high resolution archive, and shows a strangely collapsed and fractured crater floor. In fact, like a number of other Martian craters, rather than having a central peak, the center of the crater floor, shown at the image’s center right, seems depressed.

The crater is located in a region dubbed the Cerberus Plains, in a hilly subregion called Tartarus Colles. Of the transition zone between the northern lowlands and the southern highlands these plains comprise the second largest region.

Being in the transition zone I would guess that the geology here is strongly influenced by the ebb and flow of the slowly retreating intermittent ocean that is thought to have once existed in the nearby lowlands. As water came and went, it created a variety of shoreline features scattered about, but not in a single sharp line as we would expect on Earth. Think more like tidal pools, where in some areas water gets trapped and left behind only to sublimate away at at later time.

We can see some hints of these processes in the images of the floors of two other craters that I have previously highlighted, here and here.

With this geological overview in mind, the broken plates here remind me of features I’ve seen in caves. Mud gets washed into a passage, partly filling it. Over time a gentle water flow over the surface of the mud deposits a crust of calcite flowstone on top of the mud. Should the water flow suddenly increase, it will wash out the mud below the crust. If the crust is not very strong or thick, it will crack into pieces as it falls, and thus resemble what we see here in this Martian crater.

There are cases where the crust becomes thick enough to remain standing, which produces some spectacular hanging calcite draperies that seem to defy explanation.

The collapse in the center of the crater is more puzzling, but suggests, based on comparable-looking Earth geology, that any perched water in this canyon might have actually drained out through underground drainage, accessed through the depression.

Be warned: All my explanations above are based on what exists on Earth, and Mars is very different from Earth. The lower gravity, colder temperatures, and different chemistry guarantee that the geological processes there will not be identical. We start by using what we know here, but recognize that we need to learn more about Mars to truly understand what goes on there.

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Another spectacular landslide found on Mars

1:25 pm

Landslide in Hydraotes Chaos
Click for full image.

Cool image time! In perusing the April image release from the high resolution camera of Mars Reconnaissance Orbiter (MRO), I came across the image above, cropped and reduced to post here, of the discovery of another landslide within Hydraotes Chaos, one of the largest regions of chaos terrain on Mars. The image above was taken on February 9, 2019, and has since been followed up with a second image to create a stereo pair.

This is not the first landslide found in Hydraotes Chaos. I highlighted a similar slide on March 11. Both today’s landslide as well as the previous one likely represent examples of gravitational collapses as shown in this science paper about Martian ground water. Some scientists have proposed that Hydraotes Chaos was once an inland sea, and as the water drained away the loss of its buoyancy is thought to cause this kind of landslide at the base of cliffs and crater rims.

The past presence of water also helps explain the soft muddy look of this landslide. When this collapse occurred the material was likely saturated with water. Today it is most likely quite dry and hardened, but when it flowed it flowed like wet mud. Its size, almost a mile long and a quarter mile across, speaks to Mars’s low gravity, which would allow for large singular collapses like this.

Hydraotes Chaos itself is probably one of the more spectacular places on Mars. It sits at the outlet to Marineris Valles, shown in the image below. This gigantic canyon, which would easily cover the entire U.S. if placed on Earth, was the largest drainage from the large volcanic Tharsis Bulge to the west, where Mars’s largest volcanoes are located.
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How last year’s global dust storm changed one spot on Mars

1:36 pm

One spot on the western flank of Olympus Mons, August 2017
Click for full image.

To the right is an image taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) back in August 2017, cropped, rotated, and reduced to post here. It shows a particular spot on the western slope of the giant volcano Olympus Mons. The uncaptioned image release is entitled “Dark and Possibly Stationary Ripples in Anomalous Terrain.” The image was probably taken as a follow-up to this 2009 image to see if the the dark patches near the peaks and mounds as well as the strange wavy bands of light and dark had changed in eight years. As of 2017 however little had changed. The patches in the 2009 image seem darker, but that is almost certainly due to the lower sun angle causing longer shadows.

The slope goes downhill to the left. The wavy bands are thought to be geological layers exposed by erosion. The cause of the dark patches remain unknown.

I stumbled upon these two early images because of a third new image of this location, taken in February 2019 and spotted by me during my review of April 2019 images downloaded from MRO. That uncaptioned new image was titled “Change Detection in Olympus Maculae.” Had scientists spotted some new volcanic activity at this spot? To find out I dug into the MRO archive at this location and found both the 2009 and 2017 images.

The 2019 image is below. It is cropped, rotated, and reduced to match exactly with the image above in order to highlight any changes that might have occurred.
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Seasonal frost in a gully on Mars

12:32 pm

Frost in a gully on Mars
Click for full image.

Cool image time! The photo on the right, cropped, reduced, and brightened slightly to post here, was part of the April image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO). According to the titled of this release, it purports to show visible frost on what looks like an avalanche debris slope on the rim of a large crater. The frost is the bright streaks on the upper left of the slope.

I wonder. During last month’s 50th Lunar and Planetary Science Conference in Texas, there was one paper that I reported on that showed something very similar to this, and proposed that white streaks like this in a gully were actually exposed snow/ice. They proposed that the snow/ice was normally covered by dust, and the white streaks were where the dust had blown away to reveal the ice below. This in turn would then sublimate into gas, which in turn would cause the gully avalanches over time.

Below is a close-up of the white streaks on this rim.
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A dance of dust devils

3:42 pm

A dance of dust devils on Mars

Many of my image posts about Mars have emphasized how slowly things change there. This post will highlight the exact opposite. When it comes to dust devils, it appears they can leave their trace frequently and often, and for some reason they seem to also favor specific locations.

June 2011
Click for full image.

The string of images above are all of the same location in the southern highlands of Mars. All were taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) and can be found in the camera’s archive. I have cropped them to show the same approximate matching area. The first image in that strip above, shown at higher resolution to the right, was taken in June 2011 and titled “Possible Gully Features” by the MRO science team. This is not surprising, as the rounded hills in this image are actually the southwest rim of a large crater, and the slopes of craters have been found one of the best places to find the gullies where seasonal changes occur, all possibly caused by underground water.

From the title, it appears that the science team might have first hoped to spot either slope streaks or recurring slope lineae, the two most intriguing of these changing features. Instead, that 2011 image showed them a very eroded crater rim with a small scattering of dust devil tracks.

November 2018
Click for full image.

This lack of gullies probably reduced interest in this location. It wasn’t until seven years later, in November 2018, that the MRO team decided to take another image of this location (the second image in the strip above and shown to the right at higher resolution). This time they found a significant increase in the number of dust devil tracks.

At this point the decision must have been made to take another image of this location a month later in December 2018. I assume the scientists were curious to see if they would spot any additional changes in that one month period. This was dust devil season, so the likelihood of seeing more tracks was not unreasonable.

How many tracks appeared, and whether they were concentrated in any particular place, such as the ridge lines, would help researchers better understand what generates them, which in turn will give them a better understanding of the Martian atmosphere.

The result was astonishing.
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Thumbprints on Mars!

5:19 pm

Thumbprints terrain on Mars!
Click for full image.

Honestly, don’t ask me. I didn’t come up with the name. I found the image on the right, cropped and reduced to post here, as part of the April image dump from the high resolution camera of Mars Reconnaissance Orbiter. The uncaptioned release dubbed this “Thumbprint Terrain in Northern Mid-Latitudes,” and it is obvious to see why. The cropped image on the right focuses in on the oval white mounds that really do look like some giant child was touching a soft damp muddy surface randomly with his fingers, leaving behind raised fingerprints as the mud stuck to his fingers as he pulled them away.

Each white area seems to have a crater. I suspect these are not impact craters, but possibly mud volcanoes, as each is at the top of a mound. My hypothesis is further strengthened by the location, which is deep within the low northern plains of Mars, a place where some scientists believe an intermittent ocean once existed. These mounds could have easily formed at that ocean’s floor, or thereafter when the land here was drying out.

On the other hand, these could be from impact. Maybe they are scattered ejecta from a larger impact, landing here in a group on a wet muddy surface. The impacts might have concentrated the material around the crater, making it more resistant to erosion, which is why the craters now stand above the floor of the plain.

On the third hand, all these theories could be wrong. Have any of your own?

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Monitoring the ice scarps on Mars for changes

1:30 pm

Scarp #1 in 2011
Click for full image.

Scarp #1 in 2018
Click for full image.

Back in January 2018 planetary scientists released a paper announcing the discovery of a number of Martian cliff faces, or scarps as they called them, that all appeared to expose an underground layer of ice.

Those cliffs were mostly located to the southeast of Hellas Basin, the basement of Mars that is also advantageous for human colonization because its lower elevation means its atmosphere is thicker. (For example, that thicker atmosphere would make air transportation more practical.)

The two images to the right show what they listed as scarp #1 in their paper, rotated, cropped, and reduced to post here. The first image was taken in May 2011, with the second taken in December 2018, and was part of the March image release from the high resolution camera of Mars Reconnaissance Orbiter (MRO).

The December 2018 image was taken almost a year after the paper release, and was titled “Scarp Monitoring.” I therefore wondered whether the scientists had identified any changes. They theorize that these scarps form when the exposed ice slowly sublimates to gas into the atmosphere, causing the cliff face to collapse and retreat, which in the case of scarp #1 would be a retreat to the north. The terraces below the scarp suggest previous cliff locations. In their paper they noted evidence of some changes in the studied scarps, including some fallen boulders, as well as color changes that suggest some evolution.

The rate of that retreat is not known with precision, but based on the facts presently at hand, the scientists have estimated that it took about a million years to form this scarp. Whether any evidence of this retreat would be visible in only seven years is the purpose of these scarp monitoring images.

Do you see any difference? I don’t, but because I also don’t trust my expertise I decided to email the paper’s lead author, Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center. His emailed comments are most interesting.
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A decade of changes at the Martian south pole

1:54 pm

A decade of changes at the Martian south pole
Click for full image.

The image above, cropped, reduced, and annotated to post here, was released this week by the Mars Reconnaissance Orbiter (MRO) team. It shows the changes that have occurred at one location at the Martian south polar cap in the past decade. As planetary geologist Alfred McEwen wrote,

The south polar residual cap of carbon dioxide ice rapidly changes. This image was planned as an almost exact match to the illumination and viewing angles of a previous one we took in August 2009.

The pits have all expanded and merged, and we can just barely see the patterns in the 2009 image compared to this January 2019 picture. The 2009 image is also brighter and bluer, with more seasonal frost and/or less dust over the surface. These images were both taken in late southern summer, but our 2019 picture is slightly later in the Martian season by about two weeks.

You can get a better idea how much is changed by seeing the full image from which the above small area was cropped.
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More Martian Pits!

1:11 pm

More pits on Mars!

As I said in my last post in February showing recent pit discoveries on Mars, I could almost make this a monthly series. In the March image download from the high resolution camera of Mars Reconnaissance Orbiter (MRO) were three (maybe four) more pits, all likely skylights above lava tubes and all located near the giant volcano Arsia Mons in the region dubbed the Tharsis Bulge. The image to the right shows all three, with a possible fourth just northwest of pit #2 and visible in its full image. For the full images of the other two pits go here (#1) and here (#3). In all three cases, click on the “black & white map projected” link to see the full image with scale.

Overview map

The overview map on right shows where these three pits are located. If you compare this map with my previous overview maps from November 12, 2018 and February 22, 2019 you can see that while these pits are all found on the volcanic slopes surrounding Arsia Mons, they are all different pits. Moreover, the ten pits listed in these three posts are only a small sampling of the more than hundred already found.

Whether these pits are deadend sinks or skylights into underground lava tubes that connect is at this point unknown. It would be a reasonable speculation to assume that some are deadends, and some link to extensive tubes of varying lengths. It would also be dangerous. Mars is alien. While the geology will be based on the same physical laws found on Earth, the lighter gravity is going to produce things differently.

The three images above however do show some intriguing details.
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