What causes linear rilles?

JonClarke · Sep 23, 2004

Hi Polar 1. It now makes sense - thanks! 2. Interesting article, although not convincing for me from the evidence presented there. Evidence of antipodal effects have been reported from other bodies as well, Mercury for example. But no evidence that these have anything to do with ice. 3. That link does not work for me, sorry. 4 & 5. Ah, you were talking about a terrestrial example. Thant makes more sense. Glacial gouges are typically 2-4 orders of magnitude smaller than lunar rills, so it is not immediately evident that you can draw a link between the two. What is the largest one you know of? But you need other supporting evidence - moraines, cirques, etc. Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

newtonian · Sep 25, 2004

You all - I believe the faulty posts above are correct. If I'm wrong, that is my fault! JonClarke, Polar... - What evidence do we have of the temperature of the crust at the time of formation of rilles? Clearly, this is a hot vs. cold scenario variation.

JonClarke · Sep 28, 2004

"What evidence do we have of the temperature of the crust at the time of formation of rilles?" Interesting question newtonian. The maximum temperature is set by the fact that they are developed on solid mare basalts, which melt at ~1100 degrees. The minimum temperature would be the current ambient lunar temperature, say ~100 degrees in the daytime. Beyond these limuts it would be hard to say, athough had there been an extended period of temperatures at the high end (say 500-1000 degrees) we might find evidence for welding in the regolith. However as we have no samples from linear rilles in either the Apollo or Luna program we don't. Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Sep 28, 2004

Hi Polar The Appenine Mts, of which Mt Hadley is a part, a formed from the uplifted rim of the Imbrium basin. this their relief and morphology is controlled by structure. the only modification has been by gravity sliding, impact erosion and some mare flooding at lower levels. I don't see any ecvience for any morphologies that look like glcial erosion or deposition. Can you? Even if there were a few features that were superficially galcial, the absence of any alteration of samples from the Apollo 15 site (or any other lunar sample, whether Apollo, Luna or meteorite) by water of CO2 would argeu against such processes Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Sep 28, 2004

Hmm. Henry is not the depression at the base of the rock, it is the 500 m crater in the middle distance emerging to the right frombehind the rock. See http://www.apollomissionphotos.com/index17.html Henry to me looks like a typical impact crater. It is also some distance from Tracys (or Split) Rock, so I can't see any causal link between them. Tracy's rock has probably travelled there, either as ejecta from a large impact (larger than Henry) or a boulder that rolled down the hill. To me there looks life some sort of trough or gouge associated with it, and perhaps caused by its arrival, as one would expect in either case, but that in itself is not evidence for glacial action. You need the big picture and multiple lines of evidence for that. Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Sep 29, 2004

Hi Polar Sinuous rilles are a very different kettle of fish to linear rilles. So lets stick with the linear ones for the moment. Let's examine the linear rilles to the south of the image. They become shallow as the go north. Your hypothesis is that these are glacial valleys. I this is true one would expect to see features such as marginal moraines on the sides of the rille and terminal moraines were the debouche onto the Mare. Can you see any? If ice flowed across the mare one would also expect to see features like eskers and drumlins. Can you see any of these as well? Furthermore we would expect to find evidence for either aqueous or CO2 alteration of the floor of the mare. We have been to the edge of Mare Imbrium on Apollo 15 and the main part with Lunakhod 1. There is no sign of such alteration in the rocks visited on these missions (or any other lunar spacecraft). One of the characteristics of good science is that people hold lightly to hypotheses. If a hypothesis fails in its predictions time and time again, it must be abandoned, not matter how favoured. You need to always ask yourself: "What evidence would make me abandon this hypothesis"? In the case of glacial explanations for lunar linear rilles, how many failed predictions must it make before you will accept that is does not work? Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

btimsah · Sep 29, 2004

I said, "WINDOW-LIKE". Not that they are windows. Yes, you're right it's jpeg-artifact ridden. I want a higher quality version of this image. Could geology form the uh.. "formation" we see on that image? The thing that caught my eye was the wall. It has a flat side. -Rob ----------------------------SIGNATURE--------------------

JonClarke · Sep 30, 2004

Hi Rob You said both "windows or holes" and "window like holes". The image is blurry, there is no scale or location information. This makes it difficult to identify what is there. But it looks like a simgle series of hills and craters. There is nothing I can see that is not due to geological (or selenological) processes. Yes, there are lots of geological processes that produce straight walls or sides. Faults, fractures, veins, dykes, and layers (both sedimentary and igenous) all do so. Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Oct 2, 2004

Hi Polar That is a good question. I would suggest that thick accumulations of CO2 ice on the moon (or anywhere) would result in basal melting. Liquid CO2 is a very good solvent and therefore I would predict alteration of rocks by these liquids. These woudl result in formation of carbonates. We do not see these in lunar rocks and therefore I think thick CO2 accumulations are ruled out for this reason alone. Remember we have samples from at least ten locations on the moon. But this does not discount CO2 frosts in permantly shaded areas. IMHO, of course! <img src="/images/icons/smile.gif" /> Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Oct 3, 2004

Hi Polar This is starting to get complicated. The triple point of CO2 is -56 degrees and 5.11 atm. With increasing pressure it can be liquid at higher temperatures. At 73 atm CO2 is liquid up to 31 degrees and probably freezes at ~50 degrees. Solid CO2 has a density of 1.56. Real world CO2 ice might vary from this because of the presence of clathrates and included material (bubbles, silicate matter). See http://www.acri.fr/co2/diox-1.html Unlike water, the melting temperature of CO2 increasing with pressure, so pressure alone cannot cause melting. In a geological context a CO2 ice layer will not melt unless the geothermal gradient allows it. I have no idea what the geothermal gradient of the moon is, nor what the effect of an insulating blanket. The surface temperature at the lunar poles is -173 degrees. This is too cold to allow melting except by geothermal heating. CO2 clathrates and liquid CO2 are highly likely on Mars (http://pangea.stanford.edu/Oceans/GES206/kh_ges206paperE.pdf) but as I said, one planet at a time <img src="/images/icons/smile.gif" /> As to how stable CO2 deposits might be in the permanently shaded poles I have no idea. It is very cold, so would last a long time, I would guess. Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

silylene old · Oct 3, 2004

Liquid CO2 is a very good solvent and therefore I would predict alteration of rocks by these liquids. These woudl result in formation of carbonates. This is an interesting subject! Liquid CO2 has a very low viscosity and a very low surface tension. So it flows very easily and wets many materials quite well. I would imagine it would easily penetrate into soils or mineral crevices. The Hansen solubility parameters for liquid CO2 vary quite a lot with pressure. In general though, the Hansen parameters of liquid CO2 are similar to those of a ester solvent (e.g. butyl acetate)...and so liquid CO2 generally dissolves the same sort of compounds that organic esters can dissolve: fatty acids, alcohols, ketones and other esters. Liquid CO2 should not be a very a good solvent for salts or minerals, since it has only weak hydrogen bonding and polar intermolecular interactions (less than most esters, judging from the Hansen parameters). So I would think that the erosive capabilities of liquid CO2 would be far less than water would be, for example. I do agree with you that liquid CO2 might cause alteration of rocks to form carbonates, given the right conditions. I looked for references on this subject, but found none. It might be an interesting reasearch topic for someone to pursue. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

JonClarke · Oct 3, 2004

So liquid CO2 is a good solvent for non-polar compounds only? Interesting CO2 is a common geological volatile. In any high pressure/high temperature form - gaseous, liquid or supecritical it can cause alteration of rocks, typically carbonation. Many veins formed by fluids rich in CO2 have alteration rims of calcite, dolomite, magnesite, or some combination. For example: Mg2SiO4 + 2CO2 -- /> 2MgCO3 + SiO2 When it comes to mechanical erosion (as opposed to solutionI suspect that liquid CO2 will behave much the same as water as it is fluid flow, not solution that is the issue here. This is the essence of Nick Hoffman's White Mars models. While I don't agree with the model, T think he is correct in saying that flowing liquid CO2 will erode and transport material much like water. Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

silylene old · Oct 3, 2004

Jon: I agree CO2 can react with some minerals to form carbonates. But I don't think it will dissolve salts very well. Here are some solvent Hansen solubility parameters, for comparison: molecule.......dispersion......polar.....H-bonding liq CO2.................15.3.............6.9.........4.1 cyclohexanone.....16.8.............0............0.2 isopropanol..........15.8.............5.8.........16.4 H2O......................15.5.............16..........42.3 The solvency of liq CO2 varies a lot with applied pressure. Thus greasy compounds can be dissolved into liq CO2 at one pressure, then precipitated out at another pressure. Manipulating these differences in solubility with pressure is the subject of many patents on the industrial use of liq CO2 to separate and purify molecules. I don't know if liq CO2 at the right pressure could change in Hansen parameters enough to dissolve common ionic compounds. Possibly, I will have to check references when I get to work. As far as liq CO2 physically eroding and transporting minerals, I would expect it to be less effective than water. Why? Well in most erosion processes, water plays a chemical role in addition to physical (frictional) processes. Water does a great job in reacting with "fresh" surfaces and creates a layer of oxide or hydrated surface which prevents re-formation or re-deposition of a mineral. I just don't think CO2 would do this as well as water (yes CO2 could react to form carbonates in some cases). On the other hand, the low viscosity and surface tension of liq CO2 would let it penetrate better into fractures and crevices. But overall, I think water would erode most minerals faster. Jon, do you think there is any possibility of liq SO2, or liq H2S below the Martian surface (at high pressure)? These solvents, if they were present, would have some very interesting reactive and solubilizing properties. I know the rovers ha <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

JonClarke · Oct 4, 2004

Hi silylene Several points to think about. I agree that CO2 is unlikely to transport salts. But alteration of rocks by CO2 is an in situ reaction and does not result in solute transfer, as in the example I gave. Of course in the real world CO2 is almost always present with H2O, so you get both hdyration and carbonation going on in the same alteration system. I disagree with respect to liquid CO2 being less erosive than water. While water does react as you say, often physical erosion can at much higher rates that the chemical reactions you mention. If you play a jet of water over sand it is physical erosion that removes the sediment, not chemical. The same would be true if you used a jet of ethyl alcohol, or petrol (do not try these at home folks!!!!) . Now in the real world, chemical weathering by water does often weaken mineral aggregates, preconditioning them to physical erosion. And a considerable fraction of total erosion is by solution. However this goes beyond the simple case of a liquid moving over a substrate. If SO2 is to reactive would it not combine with rocks and form sulphates? I am not a fan of the acid mars theories either, BTW. H2S is interesting, most terrestrial H2S is formed by bacterial sulphate reduction or from volcanic outgassing. But most of the sulphur on Mars seems to be as sulphate, as on earth. The main role the H2S might play is in stripping metals out of hydrothermal fluids and forming sulphides. It is one way sulphide or deposits are formed. Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

shirazi · Nov 6, 2006

Dea all, I think the reason for the moon rille is simple as it is known and believed with over 1,400,000,000 (1/5) people in the world ! We muslims believe that moon was split into 2 halves for a short while by God as a miracle for prophet Muhammad (PBUH) about 1400 years ago. There is a chapter in Qur'an (exactly named 'The Moon' !) for that fact. It clearly reveals : Chapter - 54 The Moon (Al-Qamar) [54] In the name of God, Most Gracious, Most Merciful [54] The Hour has come closer, and the moon has split. [54] Then they saw a miracle; but they turned away and said, "Old magic." [54] They disbelieved, followed their opinions, and adhered to their old traditions. [54] Sufficient warnings have been delivered to alert them. [54] Great wisdom; but all the warnings have been in vain. [54] Ignore them; the day will come when the caller will announce a terrible disaster. ............. Hope it indicates the case. Please feel free to email me in case of more explanations: ali_moein_shirazi@yahoo.co.uk Best regards, Ali Shirazi

MeteorWayne · Nov 6, 2006

shirazi. Welcome to SDC. Here's a little etiquette hint. Reviving a Space Science and Astronomy thread with religious mumbo jumbo does not belong here. Find a thread in the Phenomena forum you can resurrect <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

brellis · Nov 7, 2006

At least I can say that I've witnessed a resurrection. <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

MeteorWayne · Nov 7, 2006

Better than an insurrection <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

pyoko · Nov 8, 2006

Sitting in a Korean internet caffe with stuff popping up while I type isn't helping. But... if the moon was a hot blob of rock, and slowly cooled, would there not be wave-type imperfections from interaction with Earths gravity and impacts? Also would these imperfections be mired into the surface when the Moon is 'almost' solid? <div class="Discussion_UserSignature"> -pyoko the duck It is by will alone I set my mind in motion. </div>

Leovinus · Nov 9, 2006

Well at least he revived a very good thread. <div class="Discussion_UserSignature"> </div>

What causes linear rilles?

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