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
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.
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..
Is water the only liquid?
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..
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
If I didn’t known any better I would say it looks like a stream was present there recently.
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
Friends:
I am writing to ask a question in hope that someone can answer it for me.
The information about the image says
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
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.
What I want to know is, who made that chunk of concrete, & when?
Where is the dust?
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)
I’m wondering if the surface gravel implies the possibility of an underground aquifer with water still in liquid form…….
The only clear evidence is that to support the usual grab for more money to carry on investigating.
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?
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.
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.
As some one else mentioned where is the dust, that concretion looks like it has been pressure washed or vacuumed for the photo shoot.?
@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?
Any trout?