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Space Forum / Space Science / April 2005Ventifacts? on the Columbia Hills
On the Spirit Sol 454 PamCam image http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html http://www.lyle.org/mars/imagery/2N166675764EFFA9C2P0894R0M1.JPG.html Look at the way all the rocks have a surface facing the same direction. What would do that? Are these wind-carved ventifacts? We are on top of hill. Martian atmosphere is vanishingly small. How much abrasive material could be carried by the wind. Granted gravity is smaller as well. Any comments? It amazes me the rover can move in that sort of terrain. This image shows the dust patterns in the lee of the stones. http://www.lyle.org/mars/imagery/2N166675291EFFA9C2P0715R0M1.JPG.html http://www.lyle.org/mars/imagery/2P166745642EFFA9C2P2514R1M1.JPG.html Gad, I just love these pictures... http://www.lyle.org/mars/imagery/2N166771472EFFA9DWP0603L0M1.JPG.html best, Michael http://aix1.uottawa.ca/~weinberg/mars > On the Spirit Sol 454 PamCam image > [quoted text clipped - 7 lines] > is smaller as well. Any comments? It amazes me the rover can move in > that sort of terrain. If the rover was looking at the same rocks from a different direction, you would still have a lot of rock faces facing the same direction. The rocks have many faces. It is called randomness. > This image shows the dust patterns in the lee of the stones. > http://www.lyle.org/mars/imagery/2N166675291EFFA9C2P0715R0M1.JPG.html [quoted text clipped - 7 lines] > Michael > http://aix1.uottawa.ca/~weinberg/mars Hi George, Me: >> >> all the rocks have a surface facing the same direction. You: >> The rocks have many faces. It is called randomness. Ok, let's deemphasize the facing the same direction business for a minute, although if you look at this picture, it seems to me most of the larger rocks have two main opposite faces both mainly facing the same way. >> http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html That could follow some underlying faulting or cracking. What caught my attention about them was they all are vaguely pyramidal-looking with polished faces and sharp edges like desert and Antarctic ventifacts. I suppose blasted or shattered rocks might have the same characteristics. I agree that in the other pictures the rocks are mostly randomly orientated. I just put those in so readers could have a look around. So, do you think they are wind-polished or shattered, or what? Michael > Hi George, > [quoted text clipped - 8 lines] > >>> http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html > That could follow some underlying faulting or cracking. What caught > my attention about them was they all are vaguely pyramidal-looking [quoted text clipped - 8 lines] > > Michael Not at all. I see lots of large and small rocks with faces that are randomly oriented. It would take a lot more data than you can glean from these photos alone to prove that a fault exists at this locality. For one thing, there is no apparent offset of beds - indeed, I don't see any beds at all. Randomly oriented blocks of rock do not indicate faulting. As for the fact that they have a "pyramid" appearance, so what? They are very angular in shape, which indicates that they have not undergone much alteration at all, and appear to only have a coating of dust on them. I suspect that nearly all of this rock is volcanic in origin. In fact, it reminds me of olivine basalt. > >>> http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html > Not at all. I see lots of large and small rocks with faces that are randomly > oriented. Well, maybe we need an objective third opinion. We should ask Eric. He has advanced visual orientation skills and he will be able to calculate the "digital angles" of the rocks -- which are apparently much better than the regular angles. >> I suspect that nearly all of this rock is >> volcanic in origin. In fact, it reminds me of olivine basalt. Spirit has been finding a lot of that, see ... http://iacgu7.chemie.uni-mainz.de/klingelhoefer/merpics/adir.jpg from http://iacgu7.chemie.uni-mainz.de/klingelhoefer/mer.html which is different from the lunar basalts, with more plagiocase and anorthsite. >> prove that a fault exists at this locality. For one thing, there is no >> apparent offset of beds - indeed, I don't see any beds at all. "Fault" was a bad word here. I was sort of thinking parallel cracks in the ground and the rocks have pushed up somehow from these parallel cracks. Its one of my pet theories, that the rocks have been pushed up from long straight cracks in the bedrock. If you look at this picture, you can sort of see in places where the rocks form lines -- there are a couple of lines of rocks leading to the top of the hill. http://www.lyle.org/mars/imagery/2N166675764EFFA9C2P0894R0M1.JPG.html If my pet theory is right, that is the rocks are pushed up from cracks in the bedrock, I accept that the bedrock is likely olivine basalt, then that would enhance the possibility that the rocks are sort of facing the same way and have the same shape and discount an alternate theory I saw somewhere that the rocks were debris blasted there from a nearby crater and randomly orientated. Before you write back again that the rocks are randomly orientated, could you at least try to find for the two rows of rocks in the image above I am referring to. They are on a small tilt from the vertical in the centre, something like two \\s leading to the top of the hill. If you have another idea about how a bunch of sharp-edged angular rocks got spread around, tell tell. Cheers then, Michael >> >>> http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html > [quoted text clipped - 5 lines] > calculate the "digital angles" of the rocks -- which are apparently > much better than the regular angles. Excuse me? Who is Eric? Does he have a special organ in his brain they everyone else lacks? >>> I suspect that nearly all of this rock is >>> volcanic in origin. In fact, it reminds me of olivine basalt. > > Spirit has been finding a lot of that, see ... > > http://iacgu7.chemie.uni-mainz.de/klingelhoefer/merpics/adir.jpg Right. Like I said before - olivine basalt > from > http://iacgu7.chemie.uni-mainz.de/klingelhoefer/mer.html "Hematite, which is found on Earth, can be formed in three different ways: in standing water; in small amounts of hot fluids (hydrothermal processes); and in volcanic rock." Right. Volcanic rock. Basalt is volcanic. What part of this do you not understand? > which is different from the lunar basalts, with more plagiocase and > anorthsite. The anorthosite occurs primarily in the lunar highlands, not usually in the Maria. But then, the lunar maria basalt contains tiO2 and a lot of iron. Why would you think that any of the basalt on Mars would necessarily be similar to basalt on Mars? And what does any of this have to do with random rock facial angles on Mars? >>> prove that a fault exists at this locality. For one thing, there > is no [quoted text clipped - 27 lines] > > Michael I hate to burst your pet bubble, but you can throw a random scattering of particles (say, angular fragments of sand-sized particles) on a table, and look at them with a hand lense and see the exact same thing. These hills are likley the remnants of some sort of lava flow in Mars' remote past that over the course of Mars' long geologic history became weathered, possibly due to frost wedging at least in part, which broke up the rock (they are likely outliars of a larger formation that has since weathered away or otherwise has not yet been encountered). The Mars wind then winnowed away a lot of the resulting sand and dust particles and exposed the rock to the surface. That the faces exhibit no wearing due to exposure to running water is telling (that doesn't mean that they weren't exposed to liquid water, just that any erosion they exhibit is not likely due to water flowing over the rocks - standing water could, however, have contributed to their decomposition via chemical erosion). The faces are angular (which indicates that haven't travel far for their orginal location, if they've traveled at all - likely they located are exactly where they were formed), and you can see that some of the basalt cobbles/boulders are in a state of disintegrating into angular fragments, which is a good indication of frost wedging. As to their orientation, there is no way to tell from these photographs whether the fracture faces on the rocks have anything to do with bedding (and therefore, whether bedding is discernable or not), and so all you can say is that these faces appear to be randomly oriented. The only way to get a proper orientation from these rocks would be by close examination of hand specimens in the field at the site in question (and even then, thin sections would likely also be required). What I see in the pictures is a pile of slowly disintegrating rubble of basalt. >>> >>> http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html >> [quoted text clipped - 9 lines] >Excuse me? Who is Eric? Does he have a special organ in his brain they >everyone else lacks? If he means this Eric the answer is no - it was just a silly comment from a simpleton who thinks he is clever. Eric Broxbourne >>>> I suspect that nearly all of this rock is >>>> volcanic in origin. In fact, it reminds me of olivine basalt. [quoted text clipped - 92 lines] >of slowly >disintegrating rubble of basalt.  SignatureEric Crew >>>> >>> http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html >>> [quoted text clipped - 12 lines] > If he means this Eric the answer is no - it was just a silly comment from a > simpleton who thinks he is clever. Eric Broxbourne Yeah. Silly me. Now that we agree on something, why don't you respond to my other post? >> >>> http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html > [quoted text clipped - 6 lines] >calculate the "digital angles" of the rocks -- which are apparently >much better than the regular angles. The angles would be significant if they involve crystalline planes such as 30. 45, 60 degrees or 1/12, 1/8, 1/6 of a revolution. Sorry this seems to be beyond the comprehension of a sarcastic reader, partly on account of my slipshod description as digital. (Eric) >>> I suspect that nearly all of this rock is >>> volcanic in origin. In fact, it reminds me of olivine basalt. [quoted text clipped - 39 lines] > >Michael SignatureEric Crew >>> >>> http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html >> [quoted text clipped - 11 lines] > beyond the comprehension of a sarcastic reader, partly on account of my > slipshod description as digital. (Eric) If you are referring to columnar jointing, it is possible, but without more direct evidence, better images, I'll stick with the random angle theory, thank you. Hi George, I am trying to figure out where we agree and disagree. We agree that the rocks are likely olivine basalt and the hills are volcanic and are in the process of weathering away. Point one that we obviously disagree on is about the alignment of the rocks in the image which you insist is random scattering. We can agree to disagree on that one, although I look at them again and still think that the faces and positions of the largest rocks are more aligned than I would expect in random scattering. http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html Point two which we disagree is my pet theory that the rocks have been pushed up from long straight cracks in the bedrock. You seem to propose that a larger formation has been eroded down possibly by frost wedging. Further you say : >> As to their orientation, there is no way to tell from these >> photographs whether the fracture faces on the rocks have anything to do >> with bedding (and therefore, whether bedding is discernable or not), >> and so all you can say is that these faces appear to be randomly oriented. All the while you decline to acknowledge the two rows of rocks in the centre leading to the top of the hill on this image. >> http://www.lyle.org/mars/imagery/2N166675764EFFA9C2P0894R0M1.JPG.html I suspect the reason why is you don't acknowledge them is the realization that these lines are tied to the bedding and suggest there are two parallel cracks there the rocks are being pushed up from, likely by frost wedging, and so that would support my pet theory of possible alignments. Hello Eric. Thanks for replying and my apologies for the little joke at your expense. In the first picture above, while the smaller rocks are more randomly placed, don't you think that some of the larger ones look a bit like peas in a pod. Just ignore the ventifacts reference. They aren't in the radar anymore. Cheers then, Michael > Hi George, > > I am trying to figure out where we agree and disagree. We agree that > the rocks are likely olivine basalt and the hills are volcanic and are > in the process of weathering away. What do you think of this Spirit rock? Could the sun, freeze 'n thawing and such be shaping these things? Why is the dark side always aligned the same way? http://marsrovers.jpl.nasa.gov/gallery/all/2/p/458/2P167024614ESFA9F4P2554R1M1.HTML We've seen this over and over early on. http://marsrovers.jpl.nasa.gov/gallery/all/2/p/048/2P130620425EFF09BVP2558R1M1.HTML http://marsrovers.jpl.nasa.gov/gallery/all/2/p/026/2P128675485EDN0327P2555R7M1.HTML http://marsrovers.jpl.nasa.gov/gallery/all/2/p/050/2P130811861EFF1000P2566R1M1.HTML > Point one that we obviously disagree on is about the alignment of the > rocks in the image - which you insist is random scattering. We can [quoted text clipped - 35 lines] > > Michael >> Hi George, >> [quoted text clipped - 7 lines] > the same way? > http://marsrovers.jpl.nasa.gov/gallery/all/2/p/458/2P167024614ESFA9F4P2554R1M1.HTML It appears to be a chunk of basalt. What more do you need to know? I have no doubt that these rocks are likely being shaped by freeze/thaw as well as some wind erosion. But that is just me. > We've seen this over and over early on. > http://marsrovers.jpl.nasa.gov/gallery/all/2/p/048/2P130620425EFF09BVP2558R1M1.HTML > http://marsrovers.jpl.nasa.gov/gallery/all/2/p/026/2P128675485EDN0327P2555R7M1.HTML > http://marsrovers.jpl.nasa.gov/gallery/all/2/p/050/2P130811861EFF1000P2566R1M1.HTML Yes. And? > >> Hi George, > >> [quoted text clipped - 6 lines] > > these things? Why is the dark side always aligned > > the same way? http://marsrovers.jpl.nasa.gov/gallery/all/2/p/458/2P167024614ESFA9F4P2554R1M1.HTML > It appears to be a chunk of basalt. What more do you need to know? I have no > doubt that these rocks are likely being shaped by freeze/thaw as well as some > wind erosion. But that is just me. But in this picture it's clear the rock was coated by the same material lying around it. And the coating was viscous enough to fill cracks and hold a shape. Then the wind later blasted the right half clean. It looks like the coating happened when water was present, and since it's still there, not all that long ago. This would suggest that the surface and the rocks may be ancient, but with periodic and fairly recent water making it's way out here and there. http://marsrovers.jpl.nasa.gov/gallery/all/2/p/048/2P130620425EFF09BVP2558R1M1.JPG Nasa has claimed that Mars should be exiting an ice age now. http://marsprogram.jpl.nasa.gov/odyssey/newsroom/pressreleases/20031208a.html So we're seeing it at it coldest and driest. During the warmest part of the ice ages I would bet Mars has an entirely different look. With many canals and craters filling in with ice capped water, numerous hydrothermal vents acting up and well, lots of opportunities for life that has retreated underground. To me the dark soil, like at Meridiani, would be the place to look for underground ice and life. Follow the water? Follow the dark soil! It's far too much of a coincidence that the dark soil and parallel ripples always are found and outline where water would stand. These craters and canyons filled up not terribly long ago. http://marsprogram.jpl.nasa.gov/gallery/sanddunes/PIA01695.html http://marsprogram.jpl.nasa.gov/gallery/canyons/PIA02398.html http://www.msss.com/mars_images/moc/E01_E06_sampler2002/nirgal/E02-02651Nirgal70.gif http://www.msss.com/mars_images/moc/5_27_98_agu_release/7707rel.gif http://www.msss.com/mars_images/moc/2004/01/24/R1102062.gif http://www.msss.com/mars_images/moc/2004/01/24/R1104134.gif http://www.msss.com/mars_images/moc/2003/11/05/2003.11.05.E0501789.gif > > We've seen this over and over early on. http://marsrovers.jpl.nasa.gov/gallery/all/2/p/048/2P130620425EFF09BVP2558R1M1.HTML http://marsrovers.jpl.nasa.gov/gallery/all/2/p/026/2P128675485EDN0327P2555R7M1.HTML http://marsrovers.jpl.nasa.gov/gallery/all/2/p/050/2P130811861EFF1000P2566R1M1.HTML > Yes. And? >> >> Hi George, >> >> [quoted text clipped - 22 lines] > and fairly recent water making it's way out here and there. > http://marsrovers.jpl.nasa.gov/gallery/all/2/p/048/2P130620425EFF09BVP2558R1M1.JPG Everything on Mars has a coating, Johnny. They call it dust. > Nasa has claimed that Mars should be exiting an ice age now. > http://marsprogram.jpl.nasa.gov/odyssey/newsroom/pressreleases/20031208a.html > So we're seeing it at it coldest and driest. This is not correct. It has been colder before. The glaciers were once much more extensive than they are today. > During the warmest part of the ice ages > I would bet Mars has an entirely different look. With many canals and craters > filling > in with ice capped water, numerous hydrothermal vents acting up and > well, lots of opportunities for life that has retreated underground. Perhaps early in its history. It hasn't been able to support running water on its surface for billions of years now because of the low atmospheric pressure. You should know this already, Johnny. > Hi George, > [quoted text clipped - 7 lines] > think that the faces and positions of the largest rocks are more > aligned than I would expect in random scattering. Aligned relative to what? All you can say is that the rock faces are at angular positions relative to one another. You cannot determine orientation with those photographs. You cannot say, for instance, that one face is a bedding plane, or that one face represents top while another represents the bottom. Because of this, there is no way you can orient them in any meanignful way without actually picking up some and looking at them. It is possible, as Eric may have suggested, that these rocks represent a weather pile of basalt that show columnar jointing. Having said that, they appear too fragmented to me to make a definitive determination with respect to that idea. > http://www.lyle.org/mars/imagery/2P166676295EFFA9C2P2404R1M1.JPG.html > > Point two which we disagree is my pet theory that the rocks have been > pushed up from long straight cracks in the bedrock. You seem to > propose that a larger formation has been eroded down possibly by frost > wedging. Yes. That is my position. In the absence of evidence of these cracks... > Further you say : >>> As to their orientation, there is no way to tell from these [quoted text clipped - 13 lines] > likely by frost wedging, and so that would support my pet theory of > possible alignments. I don't acknowledge them because I don't see them. Perhaps you could draw a line or two on the photos and point them out. I also see no cracks in the ground in any of those photos, so why you insist that there are cracks there is a mystery to me. > Hello Eric. Thanks for replying and my apologies for the little joke > at your expense. In the first picture above, while the smaller rocks [quoted text clipped - 5 lines] > > Michael |
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