More evidence of past water on Mars – an old streambed

From NASA’s Jet Propulsion Lab, some exciting news of the “picture is worth a thousand words” variety – NASA Rover Finds Old Streambed on Martian Surface

This set of images compares the Link outcrop of rocks on Mars (left) with similar rocks seen on Earth (right). The image of Link, obtained by NASA’s Curiosity rover, shows rounded gravel fragments, or clasts, up to a couple inches (few centimeters), within the rock outcrop. Erosion of the outcrop results in gravel clasts that fall onto the ground, creating the gravel pile at left. The outcrop characteristics are consistent with a sedimentary conglomerate, or a rock that was formed by the deposition of water and is composed of many smaller rounded rocks cemented together. A typical Earth example of sedimentary conglomerate formed of gravel fragments in a stream is shown on the right. An annotated version of the image highlights a piece of gravel that is about 0.4 inches (1 centimeter) across. It was selected as an example of coarse size and rounded shape. Rounded grains (of any size) occur by abrasion in sediment transport, by wind or water, when the grains bounce against each other. Gravel fragments are too large to be transported by wind. At this size, scientists know the rounding occurred in water transport in a stream.

PASADENA, Calif. — NASA’s Curiosity rover mission has found evidence a stream once ran vigorously across the area on Mars where the rover is driving. There is earlier evidence for the presence of water on Mars, but this evidence — images of rocks containing ancient streambed gravels — is the first of its kind.

Scientists are studying the images of stones cemented into a layer of conglomerate rock. The sizes and shapes of stones offer clues to the speed and distance of a long-ago stream’s flow.  

“From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep,” said Curiosity science co-investigator William Dietrich of the University of California, Berkeley. “Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we’re actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it.”

The finding site lies between the north rim of Gale Crater and the base of Mount Sharp, a mountain inside the crater. Earlier imaging of the region from Mars orbit allows for additional interpretation of the gravel-bearing conglomerate. The imagery shows an alluvial fan of material washed down from the rim, streaked by many apparent channels, sitting uphill of the new finds.

The rounded shape of some stones in the conglomerate indicates long-distance transport from above the rim, where a channel named Peace Vallis feeds into the alluvial fan. The abundance of channels in the fan between the rim and conglomerate suggests flows continued or repeated over a long time, not just once or for a few years.

The discovery comes from examining two outcrops, called “Hottah” and “Link,” with the telephoto capability of Curiosity’s mast camera during the first 40 days after landing. Those observations followed up on earlier hints from another outcrop, which was exposed by thruster exhaust as Curiosity, the Mars Science Laboratory Project’s rover, touched down.

“Hottah looks like someone jack-hammered up a slab of city sidewalk, but it’s really a tilted block of an ancient streambed,” said Mars Science Laboratory Project Scientist John Grotzinger of the California Institute of Technology in Pasadena.

The gravels in conglomerates at both outcrops range in size from a grain of sand to a golf ball. Some are angular, but many are rounded.

“The shapes tell you they were transported and the sizes tell you they couldn’t be transported by wind. They were transported by water flow,” said Curiosity science co-investigator Rebecca Williams of the Planetary Science Institute in Tucson, Ariz.

The science team may use Curiosity to learn the elemental composition of the material, which holds the conglomerate together, revealing more characteristics of the wet environment that formed these deposits. The stones in the conglomerate provide a sampling from above the crater rim, so the team may also examine several of them to learn about broader regional geology.

The slope of Mount Sharp in Gale Crater remains the rover’s main destination. Clay and sulfate minerals detected there from orbit can be good preservers of carbon-based organic chemicals that are potential ingredients for life.

“A long-flowing stream can be a habitable environment,” said Grotzinger. “It is not our top choice as an environment for preservation of organics, though. We’re still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment.”

During the two-year prime mission of the Mars Science Laboratory,esearchers will use Curiosity’s 10 instruments to investigate whether areas in Gale Crater have ever offered environmental conditions favorable for microbial life.

NASA’s Jet Propulsion Laboratory, a division of Caltech, built Curiosity and manages the Mars Science Laboratory Project for NASA’s Science Mission Directorate, Washington.

For more about Curiosity, visit: http://www.jpl.nasa.gov/msl , http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl .

You can follow the mission on Facebook and Twitter at: http://www.facebook.com/marscuriosity  and http://www.twitter.com/marscuriosity .

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If Curiosity finds some gold in that old stream bed, you know there will be a manned mission to Mars…gold fever and “go fever” are two strong forces for accelerating exploration, combined they’ll be irresistible.

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Kev-in-Uk

I would say it’s 99% likely an indication of water. However, to be truly scientific one should say that it could be derived from any ‘fluid’ transport! Will wait for the nutballs to come along and say it was the zurgons with a bloody big vax – hoovering up resources from the surface, etc, etc…..LOL
From a more serious geological view, I’m more interested in the cementation or cementitious material and if this shows ‘how’ the fluid evaporated. Also, whether the conglomerate is just a thin crust or of singificant thickness..

DAV

Is water the only liquid?

LC Kirk, Perth

Looks like a couple of nice white quartz pebbles in there. Should dolly a chunk of it up and pan it for gold. Mars that looks so like Western Australia..

Abd

I think the scale on the images is incorrect. Maybe it is correct for the pictures but not for the stones.

Imagine the uproar if Curiosity’s camera picks up something along the lines of a trilobite fossil impression!
– MJM

brandon

If I didn’t known any better I would say it looks like a stream was present there recently.

Ben D.

That plan for a manned mission began in 1989, check out this plan for the 21st century from the Bush Snr presidency period..
….
http://makezineblog.files.wordpress.com/2012/09/space-plan-scan-touched-up-001.pdf

richardscourtney

Friends:
I am writing to ask a question in hope that someone can answer it for me.
The information about the image says

Rounded grains (of any size) occur by abrasion in sediment transport, by wind or water, when the grains bounce against each other. Gravel fragments are too large to be transported by wind. At this size, scientists know the rounding occurred in water transport in a stream.

OK. I know nothing about how “rounding” occurs in water but I am very familiar with wear that occurs in fluidised beds of (mostly) silica sand.
Gravity is less on Mars than on Earth so stones would roll along on Mars more easily than on Earth.
Atmospheric density is much less on Mars than on Earth so winds of similar velocity would have much less force on Mars than on Earth. However, wind speeds are often much higher on Mars than on Earth. According to the Viking lander, on Mars the average wind speed is ~30 m/sec (108 km/hr, 67 mi/hr) and wind speeds of 80 m/sec (288 km/hr, 179 mi/hr) are not unusual. However, on Earth storms of more than 117 mi/hr are defined as hurricanes or typhoons and are rare.
Wind energy increases as the cube of wind speed so the energy of Martian wind acting on small stones and gravel would often be comparable to the energy of Earth hurricanes acting on similar stones and gravel. Also, the lower gravity on Mars would make it easier for winds to lift sand and gravel from the surface to induce a moving fluidised bed of particulates despite the lower atmospheric density. Indeed, severe dust storms are observed on Mars.
The potential for fluidisation of sand and gravel by Martian winds must be high especially when the winds are flowing through valleys. Hence, I would expect there to be occasional flows of fluidised sand and gravel moving over the Martian surface especially in valleys.
So, my question to any geologists who may be so kind as to enlighten me is
How does one distinguish between a Martian pebble that has been “rounded” by water and a Martian pebble that has been “rounded” by a fluidised flow of small particulates?
Richard

Mike McMillan

Gravel pretty much confirms it. Wonder where it came from, rain maybe?

Yes it is certainly a sedimentary deposit, water being the obvious choice of transport medium. I expect the deposit age will be found and a look higher up the sequence to find similar younger deposits and thus the time that water last flowed on the Martian surface, at least at the rover position.
Wind blown deposits tend to be all of similar size with a frosted surface and certainly no larger than course sand.
Good picture.

Phil

What I want to know is, who made that chunk of concrete, & when?

Robert of Ottawa

Where is the dust?

Jimmy Haigh

Nice. To clinch it I’d like to see evidence of sedimentary structures; cross bedding, ripples, laminations, grain size grading 9i.e., fining or coarsening upwards profiles) etc etc… Maybe these will come later…

Quick answer for Richardscourtney. The bouncing of particles is called saltation and tends to break off the sharp edges. It happens in any media transport so water or wind but the saltation in wind blown sediments is more energetic, due to higher velocities in wind, and causes the frosted surface very noticable in earth’s wind blown sands, desert dune sands exhibit this very well. Water transported clasts tend not to be very well sorted, ie a good mix of small sandy particles and larger up to quite large boulders depending on the event that caused the deposit. Gravels do not need a very high velocity to get movement and there are graphs available, probably on the web, that show the relation between clast size and water velocity.
We are assuming a river type deposit here but similar sorting occurs in turbidites forming Boumer sequences which are obvious to look at as being that type of deposit. The Mars picture does not look like that type of deposit but time will tell. Turbidites form in deep water and caused by an earthquake and driven by gravity. They can move very fast, in excess of 50mph/22.3m/s. Sorting occurs as the flow speed decays.
(That was a quick answer)

polistra

I’m wondering if the surface gravel implies the possibility of an underground aquifer with water still in liquid form…….

Dr Burns

The only clear evidence is that to support the usual grab for more money to carry on investigating.

Amos Mclean

What are the Martian polar ‘ice’ caps made of?
Could this “gravel” be evidence of fluid flows related to a previous ice age on Mars and retreating “glaciers”. The melting fluid doesn’t have to be water ….

Being totally out of my depth here, but can’t many liquids form rounded erosion? Does it have to be water?

richardscourtney

John Marshall:
Sincere thanks for the answer to my question that you provide at September 28, 2012 at 2:30 am.
I note that you said it was a “quick answer” and I do not doubt that: it was also a rapid reply and I appreciate that, too.
Clearly, such a “quick answer” leaves much unsaid, and there is one point I would like expanded please. In the interim, I will do as you say and conduct a web search but – not being a geologist – my understanding gained from such a search may be incorrect.
Your brief explanation of “mixing” and size sorting is interesting: I am reminded of the gradation of particle sizes along the length of the Chesil Beach in Dorset. But the effects as you report them seem very similar to what happens in a fluidised bed of particulates which is fluidised by air (for interest, I outline a nice – and fun – demo as a PS to this post).
Also, although the lifting force for particulates is high initially, once fluidisation of small particles initiates then additional fluidisation is easily developed because the fluidised bed has higher density (so more momentum) than air so can lift larger particles.
Hence, it seems to me that the distinction between “rounding” from water and particulate fluidisation has to be made on the basis of the surface morphology differences which you mention. I am not disputing that, but I know I would need to use an SEM to discern such surface differences between a pebble found on a beach or formed in a fluidised bed of silica sand.
So, I would be grateful if you were willing to expand on the morphological differences you would expect, please. And I stress that my request for more information is an indication of my sincere gratitude for what you have told me.
Richard
A simple fluidisation demo
Fix a gauze across the inside of a bucket (metal or plastic) such that the gauze creates a shallow lower chamber near the bottom of the bucket. The gauze can be positioned by spacers around the inside of the bottom of the bucket and can be retained in position using duct tape.
Pierce a hole through the side of the bucket below the level of the gauze and seal a pipe through the hole. Connect an air valve to the end of the pipe.
Place a lightweight object on the gauze (e.g. a plastic duck) then cover it with sand. Much sand can be used but the bucket must NOT be filled (the level of the top of the sand will rise when fluidised).
Place a heavy object (e.g. a large ball bearing) on top the sand.
Connect the valve to a compressed air supply. A suitable air compressor exists at most car filling stations and is provided for pumping up car tyres.
Switch on the air supply then slowly open the valve.
Initially nothing happens, then as the air supply is increased, incipient fluidisation occurs and the back pressure drops.
Slowly increase the air supply and true fluidisation is obtained. The bed expands so the level of the sand rises. The heavy weight sinks to the bottom and the light weight floats to the top.
In this situation it is simple to put one’s hand down through the sand and to retrieve the heavy weight so it can again be shown to sink. (If the air supply is turned off then the light weight sits on the sand and it is difficult to push a hand down through the sand.)
Continue to increase the air supply and turbulent fluidisation occurs. Voids filled with air (known as “bubbles” although they are not bubbles) flow up through the fluidised bed. The voids burst at the surface of the bed and throw sand into the air. Mixing is severe within the bed.
An object exposed in a fluidised bed of silca sand can experience rapid wear especially if the bed is turbulent. Both abrasion and erosion occur as a result of interaction with the particles so both hard and soft materials suffer surface loss.
The demo is simple and fun. It is especially amusing when shown to children if the floated object is a plastic duck which they did not know was at the bottom of the sand.

D. Patterson

Ben D. says:
September 28, 2012 at 1:21 am
That plan for a manned mission began in 1989, check out this plan for the 21st century from the Bush Snr presidency period..

Planning and engineering studies for a real manned mission to Mars began with Wehrner Von Braun’s Mars Project at various stages in 1946, 1948, 1952, 1956, other intervening years, and 1969. The 1969 planning set a date in 1987 for the landing on Mars, but it too was cancelled like all preceding plans due to the lack of political support. Those of us lobbying Congress and the White House for funding in 1971 barely succeeded in securing funding for the development of the Space Shuttle (STS). We were unable to save the funding for the final Apollo Lunar missions, much less find any bipartisan support for a Martian flight programme.
Later manned missions to Mars suffered similar fates with the lack of political will and support in Congress.

Tony Mach

DAV says:
Is water the only liquid?
No.
But what other potentially liquid substances are there on Mars to account for this?
Well there is lots of water in the soil in and around the polar caps.
And all of the chemistry findings so far (by all orbiters and all the rovers) say that there has been liquid water in the past. We’ll see what Curiosity finds, as she has an geo-chem lab on board.
There was extensive talk about this on the Planetfest 2012, you should look at the videos!
So I think streams of liquid water are the “better” explanation (cf. Occams Razor) for all the evidence that was gather – better than alternatives like say CO2 (which may account for some of the contemporary landslides in dunes).

John Marshall, that is a “Bouma” sequence.
In answer to Richardscourtney, There is a feature of aeolian sedimentation know as ‘desert pavement’, wherein all but the coarsest clasts are moved by the wind, leaving a surface armored with sandblasted pebbles and cobbles. This surface resists further wind erosion.
The postulated fluidization would have two populations of clasts; those which move by saltation or bedload and those that move by suspension. The suspended portion would eventually outrun the bedload, as it does in a turbidite. A resulting horizon anywhere in the deposit would be relatively well sorted, with grain size diminishing upward and downflow.
The pictures show what appears to be a well-indurated AND poorly sorted rock, with larger clasts suspended in a finer matrix. Such poor sorting indicates that the mechanisms of sorting were episodic, not sustained, that all available material was moving at once, as in a debris flow or flash flood. Gravels that form in sustained and long-lived flows tend to be well sorted, with clasts imbricated against each other. There doesn’t appear to be much of this fabric in the indurated part.
Rounding requires sustained abrasion, and is proportional to grain size (mass) and distance of transport. Rounding may occur in many episodes of transport, deposition, erosion and transport.
The induration requires some form of cement, and if the composition of the cement can be determined, then one can narrow down the candidates for the fluid phase. Suffice it to say that the fluid had to have a viscosity and kinetic energy able to move poorly sorted sediment, and was probably a liquid.

wayne Job

As some one else mentioned where is the dust, that concretion looks like it has been pressure washed or vacuumed for the photo shoot.?

Hector Pascal

@richardscourtney
There’s no definitive answer to you question. Rocks which have been eroded by wind driven sand are called ventifacts. On Earth, these have distinctive concave “scalloped” surfaces and they are quite common in desert areas. I would be looking for these features in boulders too heavy to be moved by wind, or fixed outcrops. The Sphinx is probably the best known example of a ventifact.
I don’t know of ventifacts being rounded like the example above, but that doesn’t mean they don’t exist. Diagnostic features of channel deposits include poor sorting, laterally discontinuous bedding and numerous erosion (cut and fill) surfaces. In grave/cobble dominated braided systems, (essentially transport fluid poor, sediment-rich) actual cross bedding may be quite rare.
This one looks quite convincing, but I’d like to see longer sections across and down stream. I wonder what the conglomerate cement is. Calcite? Gypsum?

Gary

Any trout?

richardscourtney

Friends:
I write to provide thanks to all who have attempted to answer my question. I hope others will also try to help my understanding.
I am minded that confirmation bias is always a problem which is difficult to avoid.
I am material scientist who is very familiar with wear in fluidised beds so when I look at that photograph I see what looks like a slumped fluidised bed. Indeed, what I am seeing on that photograph looks very like a slumped fluidised bed. This is possibly my confirmation bias: I see what I know.
And I have seen videos of fluidised beds with high flow rates happening naturally on Earth; i.e. pyroclastic flows from volcanoes and Alpine avalanches. So, I find no difficulty imagining such fluidised beds running across the surface of Mars with its lower gravity and higher wind speeds.
You geologists helping me to learn about this Martian deposit are very familiar with sedimentary deposits. When you look at the photograph you see what looks like a sedimentary deposit. And your knowledge of geological processes is much greater than mine will ever be, so your interpretation is probably right. But, of course, you may have a confirmation bias, too.
Your responses to me have all been considered, helpful and informative. I am truly grateful for each of them. But, so far, your responses amount to “It looks like a duck” when I am saying “It looks like a goose”. I would like a response akin to “It quacks like a duck, and does not honk like a goose”.
Richard

KevinM

Temperatures on Mars range -87 to 0 degrees C. How does water form and flow in an environment like that?Could this be super-well-preserved 5 billion year old remains from the heat of planet formation, or a giant solar flare or something?

Joe Guerk

Given mars’s low gravity, and thus low air pressure, how long can water remain liquid?
Should we be imagining that mars at one time had roaring rivers and huge lakes? Or did the water boil off as soon as it seeped out of the ground? Or what?

richardscourtney

Tony Mach:
At September 28, 2012 at 3:48 am you write

DAV says:

Is water the only liquid?

No.
But what other potentially liquid substances are there on Mars to account for this?

With respect, it does not need to be a liquid: it needs to be a viscous fluid.
This is why I am asking the geologists to try to educate me as to why the pebbles were not “rounded” by an abrasive fluid bed of sand that is fluidised by the Martian CO2 atmosphere flowing (or successively flowing) across the Martian surface.
Please note that such a fluidised flow would be much more abrasive and erosive than a flow of water.
Richard

Randy

Fantastic! And fun to see the Geologists on WUWT have a subject they can work. I think it looks like typical water transported worn cobbles. I’ve seen enough of those having spent 4 weeks mapping geology out in the Imperial Formation by Anza Borrego. Windblown sand eroded cobbles have distinct scaloping – i see a lot of that on hikes in the surrounding hills. And sand blasted and chemically etched beer bottles that are extraodinarly beautiful objects considering their humble origins. I do question the statement – “Gravel fragments are too large to be transported by wind. “. Up here in the north Mojave we have our “3/4 inch” days when wind blown pebbles take out your windshield! On those days it’s best to stay home and wonder when the roof is going to go.

Curious

I’m not sure this has merit, but have been reading in a few places that NASA has photo-shopped some of the photos of Gale Crater. What do you think? Possibility or hoax?
http://www.earthfiles.com/news.php?ID=2015&category=Science

Kelvin Vaughan

richardscourtney says:
September 28, 2012 at 1:28 am
Friends:
There you go, experience is worth more than a science degree!

richardscourtney

Kelvin Vaughan:
Please explain your ridiculous comment at September 28, 2012 at 6:45 am which has no relationship of any kind to my post which you cite.
Richard

David S

Obviously Mars’ atmosphere and all water was destroyed by global warming brought on by all those bloody SUVs http://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/NASA_Mars_Rover.jpg/250px-NASA_Mars_Rover.jpg

All those SUV’s on Mars sure have caused some climate change!

Curious says September 28, 2012 at 6:36 am
I’m not sure this has merit, but have been reading in a few places that NASA has photo-shopped some of the photos of Gale Crater. What do you think? …
http://www.earthfiles.com/news.php?ID=2015&category=Science

Is the con-spira-acy industry alive and well or what?
If a simple, Occam’s Razor-class explanation (e.g. a simple mistake by NASA in labeling pics) develops please, by all means, keep us informed.
.

Writes Anthony:

If Curiosity finds some gold in that old stream bed, you know there will be a manned mission to Mars…gold fever and “go fever” are two strong forces for accelerating exploration, combined they’ll be irresistible.

I have long said that if we find gold on the Moon, we’ll be back there in a heartbeat. Same goes for the rest of the Solar System, though it may take two or three heartbeats. Nothing like a little economic incentive to spur exploration—and settlement.
Recommended reading: John Lewis, Mining The Sky: Untold Riches From The Asteroids, Comets, And Planets: http://www.amazon.com/Mining-The-Sky-Asteroids-Planets/dp/0201328194
I know nothing of geology, but my first reaction was similar to Richard Courtney’s: winds on Mars are fierce, sandstorms common, and a strong-enough wind can lift even a good-sized pebble. However, I think they are saying that the bed of pebbles fragmented off the conglomerates. Wind and sand could have done that, but could the conglomerates have formed outside of water?
Does Curiosity have equipment that would enable its handlers to determine how old those conglomerates are?
/Mr Lynn

P. Solar

[snip . . not funny, or clever . . mod]
An, an, and if they don’t start to listen to me soon I’ll hold my breath until I make myself sick.
THEN I’ll launch an on-line survey !!!!!

Fred Jensen

KevinM asked “Temperatures on Mars range -87 to 0 degrees C. How does water form and flow in an environment like that?”. Simple answer – medieval warm period!

kadaka (KD Knoebel)

A streambed? Good. We found out what happened to a cat on Mars. Maybe now we can find out about the catfish!

Hector Pascal

@richardscourtney
“This is why I am asking the geologists to try to educate me as to why the pebbles were not “rounded” by an abrasive fluid bed of sand that is fluidised by the Martian CO2 atmosphere flowing (or successively flowing) across the Martian surface.”
That is a possibility. Outside my experience, but I haven’t done a lot of field work on Mars. Flow regime is a vast subject, from rockfall at one end to anastomosing rivers at the other. It is complicated by the probabilty that within a given system, you will find incorporated clasts that have been shaped in another (inheritance). Sometimes there are no easy answers.
One thing experience has taught me is that normally you can’t solve “the problem” from one exposure. As I mentioned above, I would like to see much more comprehensive sections in order to have any confidence in a given interpretation.
Don’t underestimate the abrasiveness of stream flow. It’s not just water moving, but the bedload and suspended load too. In mountain valleys, for example, you can find nicely rounded outcrop and boulders that haven’t moved very far at all.
In short, nice image but not definitive.

P. Solar

[snip . . mod]
I bet they think if they told us that CO2 could… no well maybe that’s going a bit far.

If the mars landings were faked, then climate change is not happening. Maybe we need a survey….

AndyG55

“But what other potentially liquid substances are there on Mars to account for this? ”
umm.. do you mean liquid, or fluid ?
very fine dust suspended in rivulets of air is a possibility, maybe?

Björn

I do not know if I am wrong about this , but I remember being told a decades or two ago that the stuff that the colour of Marz was mainly caused by the fact that its surface material had a high content of ferrosulfid and remember thinking “ah so it is an hell of rustheap , maybe the biggest one in ever seen the neighbourhood ” and then surmising that it must have had at least some water (and maybe an hell of a lot of it ) , because the only process I knew of that could make Iron rust requier’s , that it is in some contact with water (liquid or gaseous ). This was a few years before NASA managed to land a crawler there , and the guy who told this snippet about the ferrosulfid said this fact came from a number of spectroscopic analysis of light reflections from itś surface, and I was not intrested enough to try to verify his word about this, just took it as good solid truth. I do not know if it still holds or if the rovers have found the surface to be something else than rusty,in fact I have not given this any thought for quite a number of years, but if marz is really rusty , the I think it lends some credence to the hypothesis that it was also a little wet onse upon a time.

P. Solar

P. Solar says: “The 100 mph winds will soon be common place on Earth too. ”
Oops, I just checked with Professor Yackel, expert climatologist/geologist at U. Calgary, and that should have read “one million mph winds”. My bad. 😉

D Böehm

Proof of water on Mars.

b a cullen

This stream bed doesn’t appear to be any different from those seen in many years of photos from the other Mars rovers. Some even show puddles and recent flow, i.e. hrs vs. “millions” of years here. If you can believe it, there are photo’s from orbit of ponds and lakes, apparently unfrozen.
Remember, the comments are from Never A Straight Answer/JPL.

Chuck Nolan

This is why I come to WUWT.
cn

Steve P

The abundance of channels in the fan between the rim and conglomerate suggests flows continued or repeated over a long time, not just once or for a few years.

…with my emphasis on repeated
Hmmm. Episodes of ice sheets on Earth, floods on Mars…