Burns cliff

Hi mann

re post 54. I agree that the dark streaks are probably haematite as they look so similar to the concretions.

Cheers

Jon

Sorry mann - that should have been post 55

Hi robert, re post 56.

Thanks for the links.

The first is a fantasy site and therefore not germane to the issue. The second distinguishes between silt sized deposits of loess and sand sized dune deposits. The third does not make clear the nature and context of the "silt dunes". The fourth link shows how source bordering "silt dunes" of the Missouri river are made. In such cases the silt is deflated, transported and deposited as sand-sized aggregates, even if that link does not make it clear. The fifth link is in error when it talks about "silt dunes" as loess deposits, to which the page links "silt dunes", whether in the US or China, do not form dunes but topography-mantling blankets. The sixth link does not contain any reference to dunes at all that I can find. Neither does the seventh, which simply talks about aeolian silt burying topography.

It is important to recognise that "silt dunes" is often used as a kind of shorthand jargon. The term "clay dune" is been similarly been used elsewhere. Unfortunately is rather sloppy. It is worse when semi-popular or non-scientific articles refer to any mound of wind deposited material as a "dune" when in many cases they are not.

To the best of my knowledge silt-sized material, entrianed, transported, and deposited as such, does not form dunes, although they do form other deposits. Dunes require sand sized grains. But I will check the relevant literature tomorrow. The physics of blown sand is well understood, since the benchmark studies of Bagnold in the 30's.

Cheers

Jon

Er, jon are you this Jonathon Clarke?

Are there any particular images you would like processed? Perhaps you already have daily access to NASA science images?

In any event, thanks for hanging around the blog and providing professional commentary.

It is a crash course in Areology for this old pachyderm.

I will now slip down from my perch and do a few more 3D color pans...

(That is one sharp saw you carry in your knapsack.)

Guilty as charged your honour!

Can I say how much I enjoy your images - we have got so much we can learn from each other.

Cheers

Jon

The expedition that Thai Troung refers to in the interview has a web page at http://chapters.marssociety.org/canada/expedition-mars.org/ExpeditionTwo/journals/photos.php .

Thai was one of a group of students who came on the first part of the expedition and were great fun to have. For some reason he got my name wrong, it's Jonathan

Cheers

Jon

L2/L5 3 image Pan:

Large (1.8 MB) version

Small (0.5 MB) version

I was going to post the PNG made from the original TIF panorama -- but the PNG file is 5.6 MB and the only difference is you can see the original compression artifacts better at high magnigication. Sheesh.

There is a difference in the color of the gray silt between the 2nd and 3rd image. There simply weren't enough bits to twiddle to match the color and contrast correctly. NASA's 12 bit versions should look better.

Oh, the Areology: The fine dust is sure doing a fine impression of fluid flow.

Does anyone know just how close the equations of fine dust moving under low gravity and wind in a dry, cold, low pressure environment match the equations for water flow in a warm, wet, high pressure high gravity environment?

These patterns look too damn familiar notto to have a close analog.

Hi Jon,

It is a pleasure to be able to electronically converse with someone of your status and distinction.

In regards to reply #63:

Thank you for clarifying, While I am a professional geologist in several states, aeolian geology is definatly not one of my strong points. I may not be able to distinguish between a field of silt mounds deposited by the wind and a field of silt dunes deposited by the wind.

However, I would still call a mound of silt deposited by the wind "dune-like" as I did in Reply 56:

"Silt does not have to be aggregated to sand sized particles in order to form/be incorporated into dune-like structures by the wind."

Best regards,
Robert

Hi Robert

My expertise in aerology is very minor and largely a sideline. My daily job is salinity hazard mapping and mitigation. What do you work on

Dune like I can live with, Some may be real dunes also.

Cheers

Jon

John,

What is your take on the various rock slabs which seem to have signs of muddy fluid weeping from their down crater sides. They all show what looks like a buildup of mud and in the mud buildups several "High Water" marks.

This one is just below Burn's Cliff:

This one was seen as Oppy drove down the carter:

I would appreciate your and the others take on what appears to me to be muddy fluid flow sites / events.

Horton,

Are there enough filter shots to make a colour photo of this rock slab with it's weeping down crater edge?

Er, see upper left of image in reply 67 for the area in reply 71...

Here is a L2/L5/L7 image of the same area as reply 71.

Horton,

The rock slab with the weeping down crater edge is a bit further to the left than the area shown on your image in post 67:

The right most side of this photo is almost the left most side of your image in post 67.

Jon,

I currently work as an environmental consultant identifying and cleaning up contaminated properties. I worked at the Field Museum of Natural History in Chicago for a time as a starving paleontologist and enjoy geology, biology, meteoritics, and planetary science as hobbies.

Horton, Wow! thanks for another excellent horticolor image!

I'm looking at your image and I see a few rocks that seem to have been simply laid down upon the landscape.....

Could some of these rocks be similar to Earth glacial erratics??? Glacial erratics are rocks that were held up by ice during ice ages on Earth and when the ice melted they were "laid down upon the landscape" below them.

If there are the equivalent of "glacial erratics" at this lattitude on Mars it would be very interesting...not too surprising though.

Could Wopmay and some of the other rocks suspisciously dotting the interior of Endurance be the Mars equivalent of glacial erratics???

L2/L5 image of reply 71.

As this is a two color image, I would tend not to trust any of the colors.

Thanks Horton,

Here is the cropped version rotated 25 deg CCW. Your two image version shows up more detail of the "Mud Lip" and the row of BBs which have been pushed to the left edge of the "Mud Lip" by muddy flows from under the rock slab:

I sure wish you could do a colour image of the bigger cousin Oppy photographed on its way down the crater wall.

Four views of a possible recent mud flow event.

Looking at the level of the rock slab involved, it would appear the down crater end of the rock slab is SINKING into the crater wall. Could this be due to soil being removed from under the rock slab due to many muddy flow events?

I apologize in advance for posting these images again but I feel the impact is greater if ALL the images of this rock slab and the mud flow event are presented at one time.

3 Frame L2/L5 panorama (1.9 MB )

Try as I might, I can not imagine a gravity/ wind driven dust flow that would mimick the "weeps" I see on the left side of this image.

There are distinct changes in the soil color where the rover track ran over the "weeps".

Usual color by horticolor warning: Things may not be what they seem.

Before I get the usual whines about the calibration target color chips being the "wrong" color, I will remind everyone that the "red" is from the L2 filter ( near infrared), the "green" is from the L5 filter ( green enough) and blue is synthesized from L2 and L5 as 2*L5-L2 ( approximately).

I thought of doing a full color pan from the images ( see Ustrax's excellent 2nd B&W Pan from the color images I have done, but, the technical problems of matching the frames for a nice panorama are insurmountable.

If anyone wishes individual frames as PNG images, let me know which ones and I will post them.

I chose JPG 95% quality because even a small 3 frame full size color png is too big.

Wow, these images are fantastic! There is so much going on in there. There is that beatufiul contact in the background in horton's pos 67. The resolution is so fine it is like being there! And, in 79, it looks like most of the in situ spherules are on stalks.

The dark sandy flow like features in 67 are amazing, I still don't get why they are doing that. But, I have one other terrestrial analogy, I've seen ice do that on a cliff face, if it is near equilibirum with metling and thawing. And, we need to rememebr those rocks are going to be relatively hot during the day, even if the air temperature is very low. The air is so thin you are not going to get much thermal energy transfer through convection, so it almost does not matter how cold the air is, it is too think to make a difference. The important temperature is the actual ground temperature, the rock itself. And, when it absorbs thermal energy from the sun, it can only radiate it directly as IR. It is almost like it is under a green houst. And, of course, evaporation, or sublimation, of water would be a BIG way for the ground to lose energy, if there is enough water in it, which I think there is.

There has got to be some water here, either as ice, or brine, or more likely absorbed into the sulfate matrix itself.

But, anyway, cliff faces will form these well defined vertical ice features, basically an icicle adhering to the rock face. Ice tends to form features that appear to flow just like water a lot of the time, anyone who lives in a cold climate knows what I am talking about. The surface melt and freeze action makes it do this.

But, anyway, this is great stuff!