Martian Muddy Waters

No… Martian Muddy Waters is not an extraterrestrial blues musician.  It’s just a catchy title that links Mars, mud and water together.

pia21261

The network of cracks in this Martian rock slab called “Old Soaker” may have formed from the drying of a mud layer more than 3 billion years ago. The view spans about 3 feet (90 centimeters) left-to-right and combines three images taken by the MAHLI camera on the arm of NASA’s Curiosity Mars rover. Credits: NASA/JPL-Caltech/MSSS

Guest post by David Middleton

Clear as mud: Desiccation cracks help reveal the shape of water on Mars

BOULDER, CO, USA: As Curiosity rover marches across Mars, the red planet’s watery past comes into clearer focus.

In early 2017 scientists announced the discovery of possible desiccation cracks in Gale Crater, which was filled by lakes 3.5 billion years ago. Now, a new study has confirmed that these features are indeed desiccation cracks, and reveals fresh details about Mars’ ancient climate.

“We are now confident that these are mudcracks,” explains lead author Nathaniel Stein, a geologist at the California Institute of Technology in Pasadena. Since desiccation mudcracks form only where wet sediment is exposed to air, their position closer to the center of the ancient lake bed rather than the edge also suggests that lake levels rose and fell dramatically over time.

“The mudcracks show that the lakes in Gale Crater had gone through the same type of cycles that we see on Earth,” says Stein. The study was published in Geology online ahead of print on 16 April 2018.

The researchers focused on a coffee table-sized slab of rock nicknamed “Old Soaker.” Old Soaker is crisscrossed with polygons identical in appearance to desiccation features on Earth. The team took a close physical and chemical look at those polygons using Curiosity’s Mastcam, Mars Hand Lens Imager, ChemCam Laser Induced Breakdown Spectrometer (LIBS), and Alpha-Particle X-Ray Spectrometer (APXS).

[…]

The Geological Society of America

1814-oldsoaker-sm

“Old Soaker: Mastcam image of the Old Soaker rock slab taken on Sol 1555. The red-toned bed is covered by ridges that are the remnants of sediment that filled cracks that formed in drying lake in Gale Crater some ~3.5 billion years ago. The slab is about 80 cm across.”  GSA

Mudcracks are very interesting for two reasons.  They indicate that:

  1. Water was present in the past.
  2. Mud was present in the past.

The mud is actually more interesting than the water.

Early land plants led to the rise of mud

Mud rocks increased in riverbeds as rootless plants spread around 458 million years ago

BY CAROLYN GRAMLING, MARCH 1, 2018

Magazine issue: Vol. 193, No. 6, March 31, 2018, p. 9

Early plants made Earth muddier. Ancient riverbed deposits of mud rock — rocks containing bits of clay and silt smaller than grains of sand — began increasing around 458 million years ago, around the time that rootless plants became common across Earth, researchers say.

Anecdotally, geologists have long noted that early sediment deposits became muddier at some point, and suggested a connection with plants (SN: 6/22/74, p. 398). But no one had ever pinpointed when that muddening happened.

So geologists William McMahon and Neil Davies, both of the University of Cambridge, decided to look for when amounts of mud rock began increasing in 704 ancient river deposits from 3.5 billion to 300 million years ago. The researchers searched through nearly 1,200 published papers for data on mud rock in river deposits, and collected new field data at 125 ancient river outcrops. At those outcrops, the researchers calculated the percent of mud rock in the overall deposit by measuring the thickness of the muddy layers compared with the thickness of layers containing larger grains such as sand.

The resulting fractions showed the median mud content was about 1 percent before around 458 million years ago. At that point, the mud content steadily increased over about the next 100 million years or so to reach a median of about 26 percent in outcrops dated 359 million to 299 million years old, McMahon and Davies report in the March 2 Science.

That steady upsurge suggests that neither cyclical nor episodic forces — such as glacial-interglacial changes or tectonic events — could have driven the increase in muddiness. Instead, plants are the likeliest culprit. A primitive group of rootless plants called bryophytes, which includes modern mosses and liverworts, had likely become common by about 458 million years ago. Rooted plants further increased the mud content when they arose and began to spread around 430 million years ago, eventually forming great forests about 382 million years ago.

 […]

Update – From the actual paper

The article isn’t exactly right, the correlation is of the appearances of mudrocks and deeply-rooted plants.

Evolution of alluvial mudrock forced by early land plants

 

William J. McMahon,

Neil S. Davies*

Science  02 Mar 2018:

Vol. 359, Issue 6379, pp. 1022-1024

DOI: 10.1126/science.aan4660

Mudrocks get a vegetative assist

Mudrocks such as slate and shale are rarely found in stratigraphy older than about 500 million years. McMahon and Davies compiled a large database of mudrock occurrence over the past 3.5 billion years to help assess the origin of this ubiquitous rock type (see the Perspective by Fischer). Mudrocks appeared at the same time as did deep-rooted land plants. The interplay between plants and sedimentary rocks suggests that a change in erosion rate and the chemistry of sediments delivered to the oceans occurred around 500 million years ago.

[…]

However, land plants do promote the production of clay minerals and the depth of chemical weathering profiles by increasing atmosphere-substrate connectivity through rooting, through the direct secretion of organic acids and chelates, and by developing symbiotic relationships that increase the capacity of cyanobacteria and fungi to dissolve soil grains (2, 18, 21–26).

[…]

The timing relative to the appearance of plants is unlikely to be a coincidence, as plants can greatly contribute to the development and retention of alluvial mudrocks.

[…]

A fuller understanding of mudrock in the absence of vegetation is a prerequisite for any studies that invoke ancient terrestrial mudrock strata as a primary archive of geochemical or petrological data and will have implications for understanding the context and nature of mudrocks that are increasingly detected on nonvegetated planets such as Mars (8, 37).

Science

 

The primary building block of mudrocks are clay minerals and Mars has an abundance of clay minerals, much more abundant than expected.

Clay Minerals on Martian Surface Are More Abundant Than Expected

By Sarah Miller Dec 21, 2012

Clay minerals are found to be more abundant on the Martian surface than previously thought, according to a new study co-authored by the Georgia Institute of Technology.

Clay minerals are rocks that are formed when water is present for long periods of time. The presence of clay minerals on Mars was first discovered in 2005, indicating that the planet once hosted liquid water on the surface.

Now, a team of researchers has found that the planet is hosting more clay minerals than expected. The research team has detected the presence of clay in some of the rocks studied by Opportunity Rover when it landed at Eagle crater in 2004. But the rover detected only acidic sulfates in the rocks and since then moved to Endeavour Crater, a place NASA’s Mars Reconnaissance Orbiter pinpointed for clay minerals.

Using spectroscopic analysis from the Mars Reconnaissance Orbiter, the research team was able to identify the clay minerals at Eagle crater. They also found that clays also exist in the Meridiani plains, through which the rover trekked towards its current position.

“It’s not a surprise that Opportunity didn’t find clays while exploring,” James Wray, a faculty member at the Georgia Institute of Technology and a member of Curiosity’s science team, said in a statement.

We didn’t know they existed on Mars until after the rover arrived. Opportunity doesn’t have the same tools that have proven so effective for detecting clays from orbit.”

[…]

Nature News

Prior to the Mars Reconnaissance Orbiter’s discovery of clay minerals, they weren’t even looking for them.  The Opportunity Rover wasn’t equipped to identify clay minerals.

While this doesn’t necessarily mean that plant life once existed on Mars, it does elevate the probability a bit.  And, ironically, the mudrocks are actually the best places to look for evidence of past life on Mars.  Now if we can just find those rascally Silurians.

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MarkW

Could it be the Silurians who are hiding in the deep oceans?

Tom in Florida

Perhaps they have disguised themselves as missing heat.

Bryan A

Now stop being Ursillians

Bryan A

Here are some Close-ups from ChemCamcomment imagecomment image
And a slightly larger Color viewcomment image

DonM

Bryan,
those photos clearly show cross-fencing. The obvious deduction is a competing agrarian community of very tiny Martians. Based on the photos, anthropologists are now able to formalize their opinions about the religious culture of this specific tiny Martian community.

Latitude

…little bitty rice paddies

MarkW

Those surfaces look like reptilian skin to me.
I think we have found the Silurians.

Rootless plants on Mars…..I ask you, how silly can you get?
These mud cracks have nothing to do with plants, the cracks are filled either by silica (quartz) or by calcite! Inorganic substances! What’s the problem???

Chimp

MarkW April 20, 2018 at 8:05 pm
By George, I think you’ve got it!
Forget about plants. The surface of Mars is coated in reptilian skin!

“These mud cracks have nothing to do with plants, the cracks are filled either by silica (quartz) or by calcite! Inorganic substances!”
Yes but they may have something to do with marine organisms.
Calcite is the primary constituent of the shells of marine organisms, e.g., plankton (such as coccoliths and planktic foraminifera), the hard parts of red algae, some sponges, brachiopods, echinoderms, some serpulids, most bryozoa, and parts of the shells of some bivalves (such as oysters and rudists)
And why is calcite inorganic? It’s a carbonate mineral. Isn’t organic carbon-based?

Duster

Dr. Strangelove, I think if you dig into the history of it, the “organic” designation has more to do with the early petroleum industry than with geochemistry or biochemistry. At least that is what I recall from my classes, but that was a long time ago and the professor was a crypto-abiogenic booster.

ShrNfr

Yes, this article does muddy the waters a tad, doesn’t it??

HotScot

David
“Clay Minerals on Martian Surface Are More Abundant Than Expected”
Funny that, I guess humanity doesn’t know, what it doesn’t know.
Imagine that!

Tom in Florida

“We didn’t know they existed on Mars until after the rover arrived. Opportunity doesn’t have the same tools that have proven so effective for detecting clays from orbit.”
Robots, computers and models can only do what we program them to do so of course Opportunity didn’t have the correct tools, they didn’t know it needed them. What else don’t they program due to lack of knowledge?

Richard

Couldn’t somebody have done some climate modelling to find out? Even Mars is a globe, and so deserves deserves to be warmed, silurogenically. I mean, climate changed, silurogenicslly. My bad!

J Mac

Every farm kid who has squished mud between his toes, in a muddy low spot with drying mud around it, will recognize that image immediately.
Mars is showing itself to be/have been more like Earth than most supposed.

DonK31

In my admittedly ancient experience, these squares are the drying skin over a low spot that has not yet completed drying. As with a sponge, if you add water to ground it expands. As it drys it shrinks. The top drys first; leaving square and desiccating pieces of future dust.
If there is no rain for another week or so and if farm equipment continually rolls over the dried dirt it turns to dust. The dust can be so fine that walking through it barefoot is like walking through talc.
If these squares occur on Mars the ground has not completed drying.

Chimp

There is a lot of water ice under the thin surface of Mars. In briny solution, it can even now and then briefly turn liquid.
https://www.space.com/17048-water-on-mars.html

Duster

Your experience is pretty accurate, but … if the skin dries hard, and then the skin is either abruptly flooded with a dose of really muddy water, or is buried under aolian dust, then the skin surface can be preserved as it appeared when exposed, the same way fossil tracks are preserved. The integrity of the skin depends on clay content. With little clay, the surface wil tend to crumble or erode easily. but we make ceramics out of clay for a reason. So, if your puddle were in clayey soil, or outright clay, it can be very stable. In the Bet Netopa valley in Israel we measured “cracks” like that which were more than 10 meters deep. They were also wide enough to lose a dog, a cat, or a small child.

beng135

Don’t worry, muddy waters says everything gonna be alright:
https://youtu.be/w5IOou6qN1o?list=PL13B605BD15775187

Bryan A


Bob Marley says so too

Philip

Maybe I am just being a bit dumb today, but someone needs to explain to me how rootless plants increase mud. There is no explanation, it is just stated — appears out of thin air.

Chimp

But the researchers wondered why the plants might have caused more mud rock to develop. They suggest such plants could have tempered the impact of wind and rain against rocks. They also think it was possible that they secreted organic acids that caused changes in soil chemistry. There is even a chance, they note, that they caused changes in landscape—altering the paths of rivers and streams, for example, by adding a stabilizing factor to riverbanks.
Read more at: https://phys.org/news/2018-03-ancient-rootless-linked-production-mud.html#jCp

Keith J

Symbiotic organisms secrete demineralizing chemicals which break rocks to minerals to release or make available elements needed for life. Take for example feldspar which contains potassium, microrhyzia or plant symbiots, have enzymes to cleave this mineral.
Mud is clay and clays serve as ion traps. Releasing these ions takes energy which of course organism derives benefit.
Life finds a way.

Duster

Mud is charateristically more than just clay and usually includes silt and fine sand; some may even lack clay
(https://en.wikipedia.org/wiki/Mudstone). The “mudrock” rubric includes rock of various textures from claystone, through mudtsone to siltstone and shale.

Chimp

It was still the Ordovician 458 Ma, so the Silurians would have to wait.

Chimp

I can’t access the full text, so can’t see their evidence for a steady, rather than stepwise, increase in muddiness. If it really is steady, without a signal from the Ordovician and Carboniferous-Permian ice ages, then they might have a case attributing the trend to rootless and rooted plants.
But, as the incidence of plants would have fallen during the ice ages, I’m not yet totally convinced. Maybe an increase in dustiness cancelled out whatever negative effect glaciations had on plant life.

Chimp

I should say solely to plants.

Chimp

I saw that, but regrettably have let my membership lapse.

Chimp

David,
Could you post their graph of muddiness over time here?
Thanks!

Chimp

Thanks a million!
The rise in muddiness is clearly not steady.
On the scale presented, can’t be sure that the initial rise is from land plants, since it could also be associated with the end Ordovician glaciation. If it started before, ie at 458 Ma, then the glaciation appears not to have affected its climb.
However muddiness decreased during the Early Devonian, then started back up again, only to crash in the Carboniferous, although apparently before the onset of the titanic glaciation of that period.

Chimp

Indeed, it zooms up again during the C-P Ice Age.

Chimp

I just noticed that I’m still an AAAS member.
But thanks for posting the graph anyway.

Tom Halla

If there is that much clay, Mars must have been wet for quite a long time.

Chimp

Clearly there was liquid surface water for a long time on Mars, maybe even a billion years. But far from enough time for plants to evolve, even rootless ones. On Earth, that took about four billion years. The smaller planet Mars might have lived hard and fast and died young, but with allowing for accelerated evolution, it still seems improbable.
I’d be surprised if even cyanobacteria ever evolved there. Had they done so, IMO there would be more evidence of a time when O2 was elevated in the water and atmosphere. Maybe such will be discovered, but as yet, not so much.
It appears likelier that Martian organisms, if any, would have been anaerobic, like early terrestrial life.

Brian Pratt

Except I think these cracks formed in buried wet sediment due to earthquake shaking. The shaking caused the sand to lose its shear strength and liquefy, and be injected upwards while the overlying muddy (red) layer shrank to accommodate the sand. These kinds of cracks are often called syneresis cracks although that is a misnomer because it refers to passive chemical shrinkage. They can be hard to distinguish from desiccation cracks, but the fill of desiccation cracks is by sediment falling in from above. This does not seem to be the case here. In Figure 4A in the open-access paper one can see differently shaped crack systems in the overlying beds. This kind of deformation is common in well-bedded, fine-grained lake deposits.

Chimp

IMO you’re right. FWIW, WINVM.

Ron Long

Not too sure Brian, dessication cracks meet at 90 degree intersections and cooling cracks meet at 60 degree intersections. Shearing in an entrapped environment due to earthquake movement would produce signs of stress orientation and I don’t see that. What fills the cracks does come from above, but it may simply be more muddy water rolling ove the surface and only depositing clay-sized sediment in the cracks. What we need is a geologist to volunteer to fly up there, maybe courtesy of Elon Musk? and phone home the answer. I would volunteer but I have a golf time reserved.

MarkW

Volunteering?

NZ Willy

Those features are likely younger than they’re saying because the Martian winds would extirpate those features over time. I’d say they’re a mere hundred million years old or less. Granted I’m no authority.

Chimp

Winds on Mars are very weak due to the thinness of the air. The windstorm scene in “The Martian” is impossible.
Also, the crater is pretty deep. The big central mountain however has been sculpted by wind erosion.

Chimp

I agree. The author and screenwriters IMO could have come up with some other more plausible catastrophe to strand the guy.

NZ Willy

Chimp, of course the Martian atmosphere is thin, but I said 100,000,000 years. Ponder how much sand & dust the Martian winds displace in that length of time.

Chimp

True. But the bottom of the crater is sheltered. The big mountain in its middle, as noted, is weathered.
And Martian air would have been denser in the past.

Moderately Cross of East Anglia

Unless I’ve missed it no one seems to have mentioned that, surely, these deposits are now solid rock preserving “fossilised” mud cracks and not just dried mud?
I vote sending geologists to Mars too – it is just too interesting to sit here endlessly speculating.

Chimp

Geology-optimized robots are easier.

And safer.

Peta of Newark

That stuff is the precursor for shale – will there be any methane under the surface if/when we get there.
That will tell you all you wanna know.
Otherwise and for students of Peta’s Theory of Climate (dirt, plants and water make climate – not sunspots cosmic rays or even carbonoxide), this news is as underwhelming as being informed that fish can swim.
Planet Earth has had (at least) two seriously close encounters will being turned into Mars, the SnowBall Earth episodes but nowadays these encounters come closer. roughly every 100,000 years. We call them Ice Ages.
They are representative of, caused by, the decline of plant growth brought on by the weathering of the available dirt
What saved Earth from becoming another Mars is that Earth has plate tectonics – Mars not so. (possibly do do with Earth being bigger/heavier)
Plate tectonics moved the continents around and set off big systems of volcanoes. Ring of Fire by example.
That created new dirt for plants to get their teeth into and in doing so create mud and as a side benefit, created a nice climate for critters just like us.
Peta’s students will now be wishing with all their little hearts that the current obsession with
a) destroying/burning plants, safe in the knowledge that they will always pop right back up again, is reined in somewhat.
b) Also that the notion of unlimited amounts of dirt (mud) that can be poisoned/eroded/weathered with ploughs and nitrogen fertiliser and then allowed to flush out to sea, is firmly quashed.
Modern farming vastly accelerates the rate of soil/dirt weathering/erosion.
If a0 and b) do not happen, one of these days the plants will not just ‘pop right back up’, an ice age will come that will not abate and Earth will become Mars II.

Chimp

The biosphere does indeed affect climate on Earth, but so do the atmosphere, hydrosphere, lithosphere and ET effects, to include the sun and the planets’ effect on it, but also the solar system’s position relative to the galactic center.
Other planets in the solar system, even those without any hope of life as we know it, have climate.

Chimp

Rob,
Are you just being tendentious, or have you really never heard of cosmoclimatology, as advanced by Svensmark, Shaviv, et al? Of the many citations:
Imprint of Galactic dynamics on Earth’s climate
https://onlinelibrary.wiley.com/doi/abs/10.1002/asna.200610650?globalMessage=0
Earth’s glacial episodes and other climatic phenomena correlate well with the solar system’s position relative to the galactic plane and center, which modulates GCR flux. There are lots and lots of papers, with data, on the subject.

Chimp

Rob,
On the contrary, they generally come from the galactic center.
Hence the name.
https://helios.gsfc.nasa.gov/gcr.html
If most came from outside the Milky Way, they’d be called Intergalactic Cosmic Rays.

Chimp

Rob,
How did you miss the map in the link?
https://heasarc.gsfc.nasa.gov/docs/cgro/egret/

Chimp

Rob,
That’s because the mendacious Mann plainly prevaricates, while the scientists Svensmark, et al, don’t.
Not just our own galactic center, but those of other galaxies produce the highest energy and most prodigious amounts of GCRs:
https://apod.nasa.gov/apod/ap071112.html
You really ought to keep up on topics about which you presume to comment.

Chimp

For instance, from just a year ago:
Sagittarius A* as an Origin of the Galactic PeV Cosmic Rays?
https://arxiv.org/pdf/1604.00003.pdf
Besides the plethora of supernovae in the center of the Milky Way, there is also its supermassive black hole, which serves as a giant particle accelerator. From 2016:
http://www.dailygalaxy.com/my_weblog/2016/03/sagittarius-a-the-particle-accelerator-at-the-center-of-the-milky-way.html

Chimp

Rob,
Why do you lie so blatantly when it’s so easy for any reader to see that fact?
I didn’t start with a nearby supernova. I started with the galactic center, which is the same place I still am.
Apparently you’re unaware that the galactic center is home to a great many supernovae, but also to the supermassive black hole at Sagittarius A*.
As I said, you really do need to keep up on astronomy and astrophysics, if you wish to comment thereupon so pompously.

Chimp

Rob,
I never said point source. That is your fake strawman.
I said the galactic center, a large region in the center of the galaxy. But a lot of GCRs do come from the SMBH there, which I guess could be considered a point source.
You’re simply wrong as wrong can be but refuse to admit it, squirming shamefully and comically instead. Your charge of shifting goalposts is classic projection, since it’s you who are slip sliding away at light speed from your original false assertion.

Chimp

Rob,
I’ve posted here repeatedly the latest research from CERN, so am familiar with their results, which do not by any means rule out the past effect of GCR flux over millions of years.
Their latest conclusion is that, given so many sources of CCNs these days from pollution and other causes, the effect of GCRs on the formation of CCNs, while still ongoing, isn’t significance.
But during the past 4.5 billion years of climate history, the effect was significant.
Nice try trying to shift the goalposts again.
Hope you’re having fun being destroyed in detail.

Chimp

I didn’t say Sag A* but referred to the center of the galaxy, a region on many supernovae, plus the SMBH. To be precise I should have said region, but my comments make clear that I referred to that. However I never said nearby supernovae, only those in the central part of the galaxy.
You OTOH asserted falsely that GCRs were omnidirectional, when in fact the vast majority come from the center of the galaxy, especially the “point source” Sag A*, where resides a SMBH. So I was right, you were dead wrong, and are not just wasting everyone’s time and mine.

MarkW

As always, Rob raises mendacious to an art form.
He actually pretends that when someone is talking about the center of the galaxy, they MUST be talking about a single, tiny point.
If Rob couldn’t misdirect and obfuscate, he would have no purpose in life.

MarkW

Rob sure does get nasty when people point out how stupid he is acting.

MarkW

Even when Chimp declares on multiple occasions that he is not talking about a point source, little Rob still declares that Chimp is referencing a point source.

bonbon

Important to hear Svensmark’s comment on Kirkby’s CLOUD Cern experiment : they physically simulated initial aerosol production and using their hpc cloud simulated the growth for their results.. Contrast is Svensmark physically followed the process. So again like the IPCC, computer models were foisted.

bonbon

And Fermi found these GCR Lobes : https://www.nasa.gov/mission_pages/GLAST/news/new-structure.html
Something real serious is going on at the Galactic center. Shaviv’s GCR modulation by the galactic density wave supernova activity, and the galactic bow-shock transitions match not just climate but biodiversity.

bonbon

Svensmark here from 03.2018 : https://www.youtube.com/watch?v=iFlNS2PX4yI
from 47:50 . Models v. Physics.

Walter Sobchak

Mud, mud, glorious mud, nothing quite like it for cooling the blood:

trevor

they don’t look like mud cracks to this geologist

How so? I’m curious, if you’ll pardon the pun, because it has sometimes seemed that NASA assumes there had to be water on Mars, and then makes evidence fit that presupposition.

Brian Pratt

I think you are both right, Max and trevor. I noted above that they look more like intrastratal deformation features caused by earthquake shock. Most cracks that geologists assume are from desiccation are no such thing. Lots of wrong interpretation out there.

Chimp

Yet IMO the evidence for liquid water on the surface of Mars in the distant past is pretty impressive and mounting, whatever might be the case with these cracks.

Chimp

David,
Correct me if wrong, but I seem to recall passages in Lyell which allow for the odd catastrophic event.
Modern geology is both uniformitarian and catastrophist. This unification might have been delayed due to prejudice against catastrophes from geologists who rightly objected to creationist “Flood Geology”.
J. Harlan Bretz, Alfred Wegener and their like-minded, free-thinking colleagues were brave people and great scientists. Like so many CACA skeptics today, swimming against the trough-feeding flow.

Chimp

David,
Of course it doesn’t. But for about 150 years, the geologic consensus was toward uniformitarianism, with catastrophism looked askance upon as too “biblical”. There was huge resistance against Wegener and Bretz. Wegener had to be accepted once seafloor spreading was discovered, since before “continental drift” lacked an obvious mechanism, much like evolution before the discovery of natural selection. Megafloods sculpting the landscape was also resisted until the evidence became overwhelming in support of Bretz’ hypothesis, to include aerial photography showing the channeled scablands of the interior PNW looking like outwash ripples.

MarkW

If you assume that the same processes that formed the earth were also at work on Mars, then since Earth had water at an early date, Mars must have as well.

Chimp

David,
As you know, a lot of genuine impact craters have been found on Earth, including big ones like the Hungarian Plain and the end Cretaceous Chicxulub.
Of course, geologic processes on our active planet make identifying some of the older ones hard.

WXcycles

Yeah, cast of original, that was not dried mud.

John Reistroffer

In general mud cracks on earth are hexagonal. The “mud cracks” in this image are not. There are many processes which could create similar textures. one that comes to mind is fractures, which often do have the geometries shown in the image.

I was always under the impression that slow desiccation cracks on a surface tend to be rectangular-ish, and cracks tend to meet at 90 degrees — with some 120s sprinkled in — while the cracks of voluminous homogeneous bodies, such as basalt flows, crack in a hexagonal pattern, yielding the oh-so-awesome columnar jointing.
This very short blurb describes the processes:
A new model explains why cracks in cooling lava tend to form hexagonal patterns.
https://physics.aps.org/synopsis-for/10.1103/PhysRevLett.115.154301

Chimp

You mean it’s not because six is a magic number?

Chimp

Awesome, ie magical.

Rob Edwards

A key feature of this photo, if its not an artifact of the processing, is the red colour of the sediment. Red beds do not appear in earth geology until 2.3 billion years ago when sufficient oxygen had built up in the atmosphere to form iron oxide.

WXcycles

Red beds in WA are at least 3.8 billion, 02 built up slowly due to lower production, not no production, it was produced much earlier than 2.3, just not enough to accumulate in atmosphere. So same seems occurred on Mars. Something was making plenty of O2 in order to get such a ‘red planet’. Unless there’s another source, it looks like life did it.

MarkMcD

Just curious as to how they figure the ‘mud’ is from circa 3 billion years back.
Mars has atmosphere and it is clear it was once a lot thicker than now.
So how would the mud NOT have been eroded by the weather? This stuff looks fresh, meaning, to my view, the cracking happened far more recently that suggested.
Dating how long ago Mars got ‘smacked’ in the South by something small but massive, forming the Tharsis Bulge on the other side of the planet might be informative as to when the water went away.
Because we still have to explain why about half of Mars is a few kilometres lower than the rest.

Chimp

Based upon prior research. Dunno if this link will lead to the .pdf of the paper:
https://gsw.silverchair-cdn.com/gsw/Content_public/Journal/geology/PAP/10.1130_G40005.1/1/g40005.pdf?Expires=1524376931&Signature=LJGwP7oeFwims8eBXYPf4dt9aPIzEMUwMgf9r3fiYAnCMUuS3hdu3BmNYBpeZ4oa~Rqqwo233zGcJplBzkOQQ~uRMma1sclm07bstdVHdtMlGU9iWiFu2w2RzJp20dF8w-EZy9jf4iQrkdTP4YafEZf-UJR0QJQoFhml6geEKntL5-i1v~4JqNZD~0YyeUuQTi8heeFZ0v8koQdKUJg0woAU2qbhtDQjY5gla6UFF96~efUfb13x7RfgJw33UO5HeIsbh0D2GxAephzmK7E6Z6Fng6a~3-cmMPUznuS36egT0tzrKVsrrPhg9~VZ6NHRM5kPY4r8OK4mZlfHCxQ4gg__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA
The kilometers-thick sedimentary succession
in Gale crater provides an opportunity to observe
changes in surface environments over extended
periods in martian history. Studies of basal strata
in the informally named Murray formation demonstrated
the presence of long-lived perennial
lakes in Gale crater at ca. 3.6–3.2 Ga (Grotzinger
et al., 2014, 2015; Hurowitz et al., 2017). Recent
facies observations at higher stratigraphic levels
(Fedo et al., 2017) may record an evolution of
the environment over time. Here we present in
situ evidence for lithified desiccation cracks in
the Murray formation, indicating that the lakes
may have partially dried in its younger history.

MarkMcD

Thanks Chimp, interesting read.
Unfortunately it doesn’t address the question – how has the landscape not eroded in billions of years? For that matter, is there actual evidence of age given nobody is there to do testing of the rock?
The PDF doesn’t address how they come up with the ages, but makes assertions as though it’s an already proven thing. We’ve seen quite enough of such assumptions based on speculation from the church of AGW.
As an aside, that pic E is rather interesting – since when do we see perfect straight lines in landscape? (the CaSO4)

Jeanparisot

Why do mud cracks only form in the presence of air? It’s been a while, but I recall scaling and cracks when doing desiccation in vacuum, albeit not of mud.
I wasn’t really controlling for that, so it’s possible that the scales formed after the vacuum was broken. Is there a specific reason you need air?

Big Al

And of course there is absolutely no sign of life …. but keep the story going !

MarkW

Absence of evidence is not evidence of absence.
What percentage of Mars’ surface has been explored so far?

MarkMcD

MarkW
I have to agree – the current state of knowledge about Mars seems replete with guesses-turned-facts. Minor fiddling around with probe-based experiments, while fascinating and valuable, do not allow any decent confirmation of current hypotheses.
I think there are WAY too many such guesses and hypothesis-turned-theory on no physical evidence to make qualifiers such as ‘almost certainly’ – as we see in AGW, they turn into ‘known facts’ very easily.