Tag: Mars

The many pits of Arsia Mons

1:57 pm

The many pits of Arsia Mons

When it comes to Mars, it appears that if you want to find a pit that might be the entrance to an underground system, the place to look is on the slopes of Arsia Mons, the southernmost volcano in the chain of three giant volcanoes between Olympus Mons to the west and the vast canyon Marineris Valles to the east.

To the right is an overview map showing the pits that have been imaged since November by the high resolution camera of Mars Reconnaissance Orbiter (MRO). The black squares show the pits that I highlighted in previous posts on November 12, 2018, February 22, 2019, and April 2, 2019. The numbered white squares are the new pits found in March photograph release from MRO.

And this is only a tiny sampling. Scientists have identified more than a hundred such pits in this region. Dubbed atypical pit craters by scientists, they “generally have sharp and distinct rims, vertical or overhanging walls that extend down to their floors, surface diameters of ~50–350 m, and high depth to diameter (d/D) ratios” that are much greater than impact craters, facts that all suggest that these are skylights into more extensive lava tubes.

Below are the images of today’s four new pits.
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Curiosity second drill hole in clay formation a success

9:53 am

two drill holes in clay formation
Click for full image.

The Curiosity science team has confirmed that their second drill hole in the clay formation that the rover is presently exploring was a success.

They have confirmed that enough material from the drill hole has been deposited in their chemical analysis hopper.

The image to the right, cropped and reduced to post here, shows both drill holes on the two different flat sections of bedrock near the top.

It seems that the science team wants to spend a lot of time in this location, as described in my last rover update. It is therefore unclear when they will move south to follow their long term travel plans.

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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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First Marsquake recorded by InSight?

1:39 pm

The InSight science team has announced that they think they have detected their first Mars quake, though it was too small to provide much information about the Martian interior.

The Martian surface is extremely quiet, allowing SEIS, InSight’s specially designed seismometer, to pick up faint rumbles. In contrast, Earth’s surface is quivering constantly from seismic noise created by oceans and weather. An event of this size in Southern California would be lost among dozens of tiny crackles that occur every day.

“The Martian Sol 128 event is exciting because its size and longer duration fit the profile of moonquakes detected on the lunar surface during the Apollo missions,” said Lori Glaze, Planetary Science Division director at NASA Headquarters.

…Three other seismic signals occurred on March 14 (Sol 105), April 10 (Sol 132) and April 11 (Sol 133). Detected by SEIS’ more sensitive Very Broad Band sensors, these signals were even smaller than the Sol 128 event and more ambiguous in origin. The team will continue to study these events to try to determine their cause.

The data so far suggests is that Mars is far quieter than Earth geologically, but any conclusions at this point would be premature.

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UAE’s space agency declares its Mars probe almost ready for launch

9:08 am

The new colonial movement: The space agency of the United Arab Emirates (UAE) today announced that its 2020 Mars orbiter, dubbed Hope, is now 85% complete and on track for making its launch window.

The Probe has already entered an intensive testing phase to ensure its readiness before the launch date, with less than 500 days are remaining for the launch. It is planned to reach Mars by 2021, coinciding with the 50th anniversary of the founding of the UAE.

Several aspects related to the design, assembly of the structure, cameras and control have been verified. So far, the Probe’s systems and components, as well as its ability to communicate with the ground station have been checked by the team. The Probe has succeeded in all the tests it has been subject to so far, ahead of the five environmental tests to be conducted on the probe from June to December 2019.

While this is likely true, we must remain a bit skeptical. Though the link goes to a Reuters Arab news source, the story appears to be entirely a copy of the press release. I know this because five different Arabian news sources used the exact same language in their stories, apparently all copying from the same release.

Thus, we don’t have any independent press in the UAE looking at what is going on here. This could be true, but who knows?

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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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Rover update: April 11, 2019

2:20 pm

Summary: Curiosity successfully drills into the clay unit. Yutu-2 continues its exploration on the far side of the Moon.

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

Curiosity drill hole in clay unit on slopes of Mount Sharp

Curiosity

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

The news this week from Curiosity is that the rover has successfully drilled into the ground in the clay unit valley the rover is presently exploring betweent Vera Rubin Ridge and Mount Sharp’s higher slopes.

The image to the right shows is a close-up of that drill hole.

The rover’s drill chewed easily through the rock, unlike some of the tougher targets it faced nearby on Vera Rubin Ridge. It was so soft, in fact, that the drill didn’t need to use its percussive technique, which is helpful for snagging samples from harder rock. This was the mission’s first sample obtained using only rotation of the drill bit.

Since my last rover update on February 20, 2019, they have been traveling for several weeks to get to a spot where they can do this drilling. The clay unit seems very soft, and almost mudlike, which made finding a good surface to drill somewhat challenging. Most of the terrain seemed too soft to drill into. It almost would be better to have a scoop, as the Viking landers had. Curiosity doesn’t really have this however. It needs to use its drill, which really is a more efficient way to get down deeper into the ground anyway.

The map below shows their recent travels.
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Results from Europe’s Trace Gas Orbiter at Mars

1:47 pm

The European Space Agency today released the results of more than a year of observations from its Trace Gas Orbiter (TGO), among which were two significant findings.

First, the orbiter detected no methane in Mars’s atmosphere, contradicting recent results from both Curiosity and Mars Express.

The new results from TGO provide the most detailed global analysis yet, finding an upper limit of 0.05 ppbv, that is, 10–100 times less methane than all previous reported detections. The most precise detection limit of 0.012 ppbv was achieved at 3 km altitude. As an upper limit, 0.05 ppbv still corresponds to up to 500 tons of methane emitted over a 300 year predicted lifetime of the molecule when considering atmospheric destruction processes alone, but dispersed over the entire atmosphere, this is extremely low.

…“The TGO’s high-precision measurements seem to be at odds with previous detections; to reconcile the various datasets and match the fast transition from previously reported plumes to the apparently very low background levels, we need to find a method that efficiently destroys methane close to the surface of the planet.”

It appears they think the Curiosity and Mars Express detections were very localized and occurred close to the surface, where TGO could not detect it.

The second significant finding is indicated by the map below, showing a global map of subsurface water distribution on Mars. I have also posted below this map a global elevation map from Mars Reconnaissance Orbiter (MRO), as the similarities and differences are important.
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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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Curiosity films partial solar eclipses by both Phobos and Deimos

10:15 am

Phobos partial eclipse of Sun

Last week Curiosity successfully captured partial solar eclipses by both Phobos and Deimos as the Martian moons crossed the face of the Sun.

The movie on the right shows Phobos eclipsing the Sun. The speed is ten times faster than real time.

The press release can be seen here. It notes how these observations, of which 8 in total have been made since Curiosity arrived on Mars, have helped pin down the orbits of both moons.

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Future of InSight’s heat probe dim

2:26 pm

Blocked after drilling down only one foot instead of fifteen, engineers are increasingly worried that they will not be able to get InSight’s heat probe past whatever is blocking to so it can begin getting data of Mars’s inner thermal environment.

They are considering a bunch of options, including using InSight’s robot arm to either give the probe a nudge to help it get past the obstruction, or even use the arm to push the probe.

None of the options are encouraging it seems.

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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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The Viking landers and its possible discovery of extraterrestrial life

9:37 am

Link here. One of the scientists involved in the Viking project has written a memoir of her experience, and the article interviews her.

Patricia Straat served as co-experimenter on one of the most controversial experiments ever sent to Mars: the Labeled Release instrument on the Viking Mars landers. The experiment’s principal investigator, Gilbert Levin, insists to this day that the project found extraterrestrial life. Most scientists doubt this interpretation, but the issue has never been fully settled.

Read it. It illustrates how uncertain science can be, even when an experiment produces a result that everyone involved dreamt of. As Straat notes,

The results met the pre-mission definition of a positive life response. But of course as soon as we got it everyone came up with alternative proposals to account for the results nonbiologically.

The problem was that though their experiment found evidence of life, none of the other Viking experiments did. Most significant was the apparently complete lack of organic material (based on carbon) in the soil.

To this day, no one has a good explanation for these results on Viking. The results remain a mystery, one that really will only be solved when we can return to Mars in force, and find out what it is really like.

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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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Mars Express confirms Curiosity 2013 methane detection

8:40 pm

The uncertainty of science: The Mars Express science team today announced that a reanalysis of the orbiter’s data showed the same spike spike of methane detection as seen by Curiosity on June 15, 2013.

The study exploited a new observation technique, allowing the collection of several hundred measurements in one area over a short period of time. The teams also developed a refined analysis technique to get the best out of their data.

“In general we did not detect any methane, aside from one definite detection of about 15 parts per billion by volume of methane in the atmosphere, which turned out to be a day after Curiosity reported a spike of about six parts per billion,” says Marco Giuranna from the Institute for Space Astrophysics and Planetology in Rome, Italy, the principal investigator for the PFS experiment, and lead author of the paper reporting the results in Nature Geoscience today.

“Although parts per billion in general means a relatively small amount, it is quite remarkable for Mars – our measurement corresponds to an average of about 46 tonnes of methane that was present in the area of 49 000 square kilometres observed from our orbit.”

Ten other observations in the Mars Express study period that reported no detections at the limit of the spectrometer’s sensitivity corresponded to a period of low measurements reported by Curiosity.

The data, along with their estimate about the source location for the methane, suggests that this was a geological event, not the result of biological life. They think the methane was trapped in ice-filled fissures, and released when that ice either broke or melted. Whether the methane itself was formed by past microbial life sometime in the past remains completely unknown.

To put it mildly, there are a lot of uncertainties in this result.

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Circular feature on Mars?

2:52 pm

A circular feature on Mars?
Click for full resolution image.

Today’s cool image is cool for two reasons. First and foremost, the image, found in the archive of the high resolution camera of Mars Reconnaissance Orbiter (MRO), is titled “Circular Feature.” On the right is the full image, reduced to post here. I have searched it high and low, at low resolution as well as full resolution, and can find nothing, nothing at all, that invokes a circular feature to me.

This strange terrain is located very close to the southern icecap. If anything, the knobs and features that fill this image remind me of brain terrain, partly obscured by a layer of partly melted snow or frost. Nothing however seems circular in the slightest.

The second reason this image is cool is that it is very representative of its very large surrounding region. For what appears to be several hundred miles in all directions this is all that one can see, in a variety of MRO images, here, here, here, here, here, and here, to show only a few. Ever so often a craterlike feature pops out, like in the last example, but generally the surface continues in this undulating bland manner, endlessly. The only changing aspect is the dark streaks that cut across, likely dust devil tracks made over a long period of time.

Below the fold is a section of the full resolution image, at full resolution. It doesn’t really matter where I took the crop, as anywhere in the full image everything looks pretty much the same. The only slow change that I can perceive is that the surface seems to be descending to the north, with the lighter areas implying the existence of terraces.

Take a look, and try to figure out for yourself what is going on here.
» Read more

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Scientists propose widespread deep groundwater on Mars

9:40 am

In a new study, scientists are now suggesting that widespread deep groundwater exists on Mars, and is the cause of the recurring slope lineae seen on many Martian slopes.

Previous theories for the cause of lineae proposed both dry and wet processes, all related to either near surface or atmospheric phenomenon. This new hypothesis is different, as it proposes deep groundwater as the source.

“We propose an alternative hypothesis that they originate from a deep pressurized groundwater source which comes to the surface moving upward along ground cracks,” Heggy says. “The experience we gained from our research in desert hydrology was the cornerstone in reaching this conclusion. We have seen the same mechanisms in the North African Sahara and in the Arabian Peninsula, and it helped us explore the same mechanism on Mars,” said Abotalib Z. Abotalib, the paper’s first author.

The two scientists concluded that fractures within some of Mars’ craters, enabled water springs to rise up to the surface as a result of pressure deep below. These springs leaked onto the surface, generating the sharp and distinct linear features found on the walls of these craters. The scientists also provide an explanation on how these water features fluctuate with seasonality on Mars.

This conclusion is most intriguing, but it is far from certain. Scientists have found a lot of lineae. For all of them to come from deep groundwater rising under pressure through fractures seems unlikely.

Nonetheless, this research indicates the growing belief among Mars researchers that water exists everywhere on Mars, and is accessible.

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Mars helicopter completes first test flight

9:28 am

The small helicopter that will fly autonomously as part of the Mars 2020 rover mission has successfully completed its first test flights here on Earth.

“We only required a 2-inch (5-centimeter) hover to obtain all the data sets needed to confirm that our Mars helicopter flies autonomously as designed in a thin Mars-like atmosphere; there was no need to go higher. It was a heck of a first flight,” [said Teddy Tzanetos, test conductor for the Mars Helicopter at JPL.]

The Mars Helicopter’s first flight was followed up by a second in the vacuum chamber the following day. Logging a grand total of one minute of flight time at an altitude of 2 inches (5 centimeters), more than 1,500 individual pieces of carbon fiber, flight-grade aluminum, silicon, copper, foil and foam have proven that they can work together as a cohesive unit.

This helicopter drone is a technology experiment, more focused on testing helicopter flying on Mars that doing science. If it proves to work, it will open up a whole new unmanned option for exploring the Martian surface. Imagine a helicopter that takes short hops from point to point. It will be able to reach locations a rover never could, and do it faster.

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How fast do things change on Mars?

12:46 pm

Looking for dune changes on Mars

On Earth, it is assumed that in a period of a dozen years a sand dune would change significantly. Wind and rain and the yearly cycle of the seasons would work their will, reshaping and moving the dune steadily from one place to another.

On Mars, we would be reasonable to expect the same. Yet, this might be a mistake, as illustrated by the two images on the right, taken by cameras on Mars Reconnaissance Orbiter (MRO) a dozen years apart of the same large dune located in a crater far to the south in the planet’s southern highlands. Both images have been cropped and reduced in resolution to show here. For the full images, go here for 2007 and here for 2019.

The top image was taken October 31, 2007 by MRO’s context camera. The bottom image was taken on January 29, 2019 by MRO’s high resolution camera. Though the context camera does not have the resolution of the high resolution camera, the difference is of less significance in this context.

Have things changed? Putting aside lighting differences, it does appear that the white patches have changed slightly in a variety of places. There also might be changes in the small dunes on the left of the image, at the base of the large central dune.

The white patches are probably what interests the scientists who requested the second image. Could this be snow or frost, as is thought to exist in other places? There are studies [pdf] that expect ice to exist inside craters near the south pole. Identifying changes here would help answer this question.

Overall, however, not much is different. Though dunes definitely change on Mars, they do so much more slowly than on Earth. And in some cases what look like dunes are not really dunes at all, but a form of cemented sandstone, exhibiting even fewer changes over long time spans.

I do not know if these dunes are of sand or sandstone. What the two images reveal is that in either case, things do not change on Mars at the same pace as they do on Earth. Even after three Martian years, the thin Martian atmosphere simply doesn’t have the same energy as on Earth, even though it can move things easier in the weak gravity.

While the pole caps of Mars change a lot seasonally, the rest of the planet evolves very slowly. Mars is no longer an active planet like the Earth. It is, in many ways, a dead planet, once alive with activity but now silent and relatively quiet.

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Rivers on Mars?

9:24 am

The uncertainty of science: A new study of Martian geology suggests that rivers ran on the surface are longer and later in the planet’s history than previously thought.

Seeking a better understanding of Martian precipitation, Kite and his colleagues analyzed photographs and elevation models for more than 200 ancient Martian riverbeds spanning over a billion years. These riverbeds are a rich source of clues about the water running through them and the climate that produced it. For example, the width and steepness of the riverbeds and the size of the gravel tell scientists about the force of the water flow, and the quantity of the gravel constrains the volume of water coming through.

Their analysis shows clear evidence for persistent, strong runoff that occurred well into the last stage of the wet climate, Kite said.

The results provide guidance for those trying to reconstruct the Martian climate, Kite said. For example, the size of the rivers implies the water was flowing continuously, not just at high noon, so climate modelers need to account for a strong greenhouse effect to keep the planet warm enough for average daytime temperatures above the freezing point of water.

The rivers also show strong flow up to the last geological minute before the wet climate dries up. “You would expect them to wane gradually over time, but that’s not what we see,” Kite said. The rivers get shorter—hundreds of kilometers rather than thousands—but discharge is still strong. “The wettest day of the year is still very wet.”

They also found that these rivers had been wider than those seen on Earth, which would make sense if there were few if any plant life to fix the banks in place, as on Earth. The lower Martian gravity probably plays an even larger role in this.

You can read the paper here. The study confirms many other previous studies of Martian surface features, which have repeatedly found evidence that liquid water once existed on Mars. That it found the water flowed later and more extensively only makes more difficult the deeper and probably biggest mystery of Martian geology, however, which is that scientists have not been able to come up with a historic atmospheric model that would allow that liquid water to exist. Mars today is too cold and its atmosphere is too thin for liquid water to flow, and the evidence from the past does not suggest an atmosphere different enough to change that.

It must have been different, but we don’t know how that was possible, based on the data we presently have. And this study makes solving that mystery even more difficult.

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Fresh crater in Martian northern lowlands

1:44 pm

Fresh impact crater in northern lowlands
Click for full image.

Today’s cool image could be a sequel to yesterday’s. The image on the right, cropped to post here, was one of the many images released from Mars Reconnaissance Orbiter’s (MRO) high resolution camera in March. The release, uncaptioned, calls this a “fresh impact crater.”

In many ways it resembles the craters I posted yesterday, with a splashed look and a crater floor with features that favor the north. Why that divot exists in the northern half of the floor is to me a mystery. The crater floor looks like a sinkhole to me, with material slowly leaking downward at that divot to cause this surface depression. Yet the rim screams impact. And yet, why the double rim? Was this caused by ripples in wet mud when the bolide hit?

Location of fresh impact crater

The crater itself is all by itself deep in those northern plains. You can see its location as the tiny white rectangle slightly to the left of the center in the overview image to the right. The giant Martian volcanoes can be seen at the image’s right edge, almost a quarter of a planet away. This is at a very low elevation on Mars, almost as deep as Hellas Basin.

For some fun context, this location is very close to where Viking 2 landed in 1976. The Mars 2020 rover meanwhile will land at this overview image’s left edge, on the western shore of the oval cut into southern highlands at about the same latitude as Olympus Mons, the largest volcano on the right. And InSight and Curiosity sit almost due south, with Curiosity in the yellow in the transition from green to orange, and InSight to the north in the green.

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Strange craters in the Martian northern lowlands

12:58 pm

Strange crater in the northern lowlands
Click for full image.

Cool image time! The image on the right, cropped and rotated to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and released in the monthly image dump provided by the science team. The release had no caption. It merely described this as a “Layered mound in crater.”

That is certainly what is is. However, layering suggests a regionwide process. The crater to the immediate northeast (the rim of which can be seen in the upper corner of this image), does not have the same kind of layering. (Be sure to click on the image to see that other crater.) Its crater floor is instead a blob of chaotic knobs, with the only layering scattered in spots along its north interior rim.

That the layering of both craters favors the north suggests a relationship, but what that is is beyond me. Prevailing winds? Maybe, but I don’t have the knowledge to explain how that process would work.

It is not even certain that these two craters were formed by impact. They are located in the northern lowlands where an intermittent ocean is believed to have once existed, and thus might be remnants of that ocean’s floor. That they both have a muddy appearance reinforces this hypothesis, but once again, I would not bet much money on this theory. The features here could also be expressing the effect of an impact on a muddy seafloor.

In either case the craters imply that the ocean that might have once been here existed a long enough time ago for these craters to form (either by impact or some other process) and then evolve. This has been a relatively dry place for a very long time.

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The layering at the Martian poles

2:56 pm

Layering in the east side of Burroughs Crater
Click for full image.

Layering in the west side of Burroughs Crater
Click for full image.

In the past month the science teams of both Mars Reconnaissance Orbiter (MRO) and Trace Gas Orbiter (TGO) have released images showing the strange layering found in Burroughs Crater, located near the Martian south pole.

The top image above is the MRO image, rotated and cropped to post here. To the right is a cropped and reduced section of the TGO image.

Though both images look at the inside rim of the crater, they cover sections at opposite ends of the crater. The MRO image of the crater’s east interior rim, with the lowest areas to the right, while the TGO image shows the crater’s northwest interior rim, with the lowest areas on the bottom. As noted at the TGO image site:
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Jezero Crater: The landing site for the Mars 2020 rover

12:21 pm

Jezero Crater delta
Jezero Crater delta

At this week’s 50th Lunar and Planetary Science Conference in Texas, there were many papers detailing the geological, topographical, chemical, meteorology and biological circumstances at the landing sites for the 2020 Martian rovers, Jezero Crater for the U.S.’s Mars 2020 and Oxia Planum for Europe’s Rosalind Franklin.

Most of these papers are a bit too esoteric for the general public (though if you like to delve into this stuff like I do, go to the conference program and search for “Jezero” and “Oxia” and you can delve to your heart’s content).

Oxia Planum drainages

These papers do make it possible to understand why each site was chosen. I have already done this analysis for Rosalind Franklin, which you can read here and here. Oxia Planum is in the transition between the southern highlands and the northern lowlands (where an intermittent ocean might have once existed). Here can be found many shoreline features. In fact, one of the papers at this week’s conference mapped [pdf] the drainage patterns surrounding the landing ellipse, including the water catchment areas, as shown by the figure from that paper on the right.

With this post I want to focus on Jezero Crater, the Mars 2020 landing site. The image above shows the crater’s most interesting feature, an impressive delta of material that apparently flowed out of the break in the western wall of the crater.

This image however does not tell us much about where exactly the rover will land, or go. To do that, we must zoom out a bit.
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Lava tubes on Alba Mons

12:28 pm

Lava tubes on the western slope of Alba Mons

During oral presentations today at this week’s 50th Lunar and Planetary Science Conference in Texas, scientists revealed [pdf] a map showing what they believe are numerous lava tubes flowing down the western slope of the giant Martian volcano Alba Mons.

The image on the right is taken from their paper. The red lines indicate collapsed tube sections, maroon collapsed sections on a ridge, and yellow volcanic ridges, which I assume are external surface flows. From their paper:

Lava tube systems … occur throughout the western flank, are concentrated in some locations, and are generally radial in orientation to Alba Mons’ summit. Lava tubes are typically discontinuous and delineated by sinuous chains of elongate depressions, which in many cases are located along the crests of prominent sinuous ridges. Lava tube systems occur as both these ridged forms with lateral flow textures and more subtle features denoted by a central distributary feature within the flat-lying flow field surface. Significant parts of the sinuous volcanic ridges show no collapse features, indicating a distinctive topographic signature for Alba Mons’ lava tubes.

Alba Mons is in some ways the forgotten giant volcano on Mars.
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Streaky Mars: Slope streaks and recurring slope lineae

12:01 pm

New recurring lineae on Mars
Click for source paper [pdf].

Numerous presentations at this week’s 50th Lunar and Planetary Science Conference in Texas have focused on two different changing features on the Martian surface, dubbed slope streaks and recurring slope lineae (or RSLs, an example of an unnecessary and unwieldy acronym that I avoid like the plague).

These apparently are considered two different phenomenon (with some overlap), something I had not recognized previously. For example, one presentation [pdf] this week described slope streaks as:

…gravity-driven dark or light-toned features that form throughout the martian year in high-albedo and low-thermal-inertia equatorial regions of Mars. The distinctive features originate from point sources on slopes steeper than ~20°, follow the topographic gradient, extend or divert around small obstacles, and propagate up to maximum lengths of a few kilometers. The streaks brighten with time, sometimes become brighter than their surroundings, and fade away over timescales of decades. [emphasis mine]

An example can be seen here. This is in contrast to the recurring slope lineae, shown in the image above, which another paper [pdf] described as:

…dark linear features that occur on the surface of steep slopes in the mid-latitudes of Mars. These areas are warm, occasionally exceeding temperatures of 273-320 K. [Lineae] recur over multiple years, growing during warm seasons and fading away during colder seasons. Their apparent temperature dependency raises the possibility that liquid water is involved in their formation. [emphasis mine]

I have highlighted the key differences. While slope streaks are long lived and change slowly, lineae change with the Martian seasons. And the slope streaks appear to exist at lower latitudes. These difference means that the formation process of each must be also different.

The problem is that scientists still don’t know what causes either, though they have many theories, involving both wet and dry processes.

Most of the presentations at the conference this week focused on the recurring lineae, which I suspect is because of their seasonal aspect. This feature strongly suggests a water-related source for the lineae, and everyone who studies Mars is always focused on finding sources on Mars where liquid water might be found. Also, slope streaks appear more often in dunes, which also strongly suggests a dry process. One paper, however, did a comparison study of lineae with one specific kind of dune slope streak to see if the freatures might be related.

The most interesting result [pdf] for all these papers documented the apparent increase in recurring lineae following the global dust storm last year. The image at the top of that post is from this paper, and shows a fresh lineae where none had been prior to the storm. From the paper’s abstract:
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Land of mesas

9:44 am

Ariadnes Colles
Click for full image.

Cool image time! The Mars Odyssey science team today released the image on the right, cropped and rotated to show here, of a region on Mars named “Ariadnes Colles.”

The term colles means hills or knobs. The hills appear brighter than the surrounding lowlands, likely due to relatively less dust cover.

This is certainly a place with lots of hills, or to be more precise, mesas, as many of them seem to be flat topped.

The lack of dust cover on the tops is probably because, like on Earth, the winds blow much better once you get a bit above the surface. (This is why sailing ship builders kept adding higher and higher sails to their ships, until the top sails of clipper ships rose a hundred-plus feet above the deck.) These better winds clean off the mesa tops, just as they did to the solar panels on the rovers Opportunity and Spirit several times during their long missions.

Ariadnes Colles is another example of Martian chaotic terrain. Since this region is located deep in the cratered and rough southern highlands of Mars, the erosion that created these mesas was likely not water-flows. Was it wind? Ice?

Your guess is as good as anyone’s.

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