Planet Four Talk

Repeating Patterns (2) Return of The Killer Fan....

  • Paul_Johnson by Paul_Johnson

    I wanted to sort out some of the comments from last night into a new thread, as the other one is mahhhoosive...

    Anya...

    Basicaly, that's what I think as well, when I see these double fans. We started this project to find out if all the feelings we got were statistically right or not. Seeing 100s of images and saying "I feel like most of them have V-shaped fans" is much weaker statement than saying "people marked 100 fans, out of those 100 this many (put number here at the end of this project) had 2 fans starting at the same source". One very possible explanation for V-shapes is that the wind direction in each location "drifts" during spring. So, first fan is from eruption early in spring and second - a bit later but when wind has already shifted. Another explanation is that it's diurnal variation of winds. First fan came in the morning, second fan came in afternoon... To distinguish we need to see how large time intervals between 1 and 2 fan. Maybe we can do that if we have enough time resolution in the places with double fans.

    Posted

  • Paul_Johnson by Paul_Johnson

    Anya...

    we know that most of fans formed in early spring become brighter with time, so their apparent size decreases. But if the fan was created in second half of spring - it never shrinks. So, I think, all proportions will depend on timing of images

    "mechanism for sealing up all the holes so that pressure can build up again or a way to generate lots of gas quickly" - and both are theoretically possible in these areas. The ice layer here is dry ice, it has a meta-morphing properties, so it tends to "heal" cracks fast if its temperature is slightly increased. And production of CO2 gas underneath of this ice is also rather efficient, because the ice it close to sublimation temperature (otherwise, if the ice would be colder the atmosphere that is made from 95% CO2 would completely collapse to the polar areas) This means, you need to warm it up only a bit to get the sublimation started. The source of the energy is debated, but solid-state green house is the favorite in the debate. Than again, it's not like we know that all the fans have to form during 1 hour or a day. Maybe they during couple of weeks is reasonable time interval? I am not ready to pin it till I get the statistics. With that interval "simultaneous" jets are not unimaginable, right? Anya

    Posted

  • Paul_Johnson by Paul_Johnson

    Anya...

    You might be right with "ratio of lobes" - we will see this from stats - but I am missing the connection to the common gas source. If you imaging that underneath each fan is a separate cavity and they all get same amount of energy for eruption, proportionality will stay, no? And in the opposite, if you imaging huge cavity underneath all the area of fans, you'd need to have same conditions everywhere - like for example, thickness of ice layer must be uniform, pressure must be re-distributed somehow not that larger holes eat up all the gas and so on. M?

    Solid state green house is like atmospheric green house but instead of atmosphere you get some solid. In our case it's ice layer. Sunlight of visible wavelength gets thought this layer and at the bottom of it it warms up the substrate, i.e. shifts in wavelength to thermal. Thermal radiation can not get out through the ice layer - and has to contribute to the sublimation. You can try to google it for more details.

    Wassock: I agree with the most of your description, apart from 3 points: 1) you still have to seal the holes otherwise you can not build up the pressure. So why would the new holes be the same size as for the first eruptions? There is a possibility that the process is constant out-gassing... I did not think this through yet. 2) I disagree that "the easiest way is to link all vents". Considering the topography of this places with all the channels and bumps. The easiest way is to think that size of lobe (i.e. gas pressure in assumption of keeping vent hole the same between eruptions) is proportional to the energy input per area. So if one fan is feeding on 1 m^2 the cavity which is 1m^3 and another one is feeding from 2m^2 the cavity of 2m^3 - the proportionality in created gas pressures will be conserved with changing energy input per are... Hope you are getting this... I am not sure I explain it clear enough. 3) the strength of the wind is something you do not consider yet. The length of fan will be largely dependent on it, maybe more than on any other parameter.

    The transparency of dry ice depends on its structure: if it's in slab form (same form of ice as water ice on frozen lakes) - the transparency is about 70% for 1m thiknes. If it's frost - much less.

    Posted

  • Paul_Johnson by Paul_Johnson

    Thanks for these comments Anya, very kind. You have given me and several others a lot to think about....

    I am surprised that you seem to agree that the eruptions appear to happen at the same time across a fanfield, it's a frankly astonishing image to think of them reaching the same critical point and going boom, as one. Then several hours/days/weeks later, boom, they all go again at the same time. This is really at the heart of the question....why? Because the gas in multiple pockets reaches sublimation point (-85.5C, or something....) at the same time, expand at the same rate and then, pop goes the weasel. The other factors in the formation of muliple similar fans seem to be...

    Wind direction.
    Wind speed.
    Aperture of hole in ice.
    pressure at source of gas.
    How quickly the hole refreezes.
    How quickly the gas reforms at the correct pressure.
    What material is thrown up and out.
    Maybe air temp.
    Ground elevation in vicinity of holes.

    Anything wrong there anyone...or missing?

    Also Anya is not hot on the Big Bubble Theory (sorry wassock....!).

    Is that were we are at, so far?

    Posted

  • Paul_Johnson by Paul_Johnson

    I must admit I thought the 'BBT' was elegant, because it seemed to describe the way fans look, astonishingly similar, same jets, same time, same place-there seemed to need to be a link between them, apparently there isn't. They behave in a similar way because they have all had similar forces, heat, pressurization, wind speed, etc act upon them. The sun heating the area beneath the ice in a solid state greenhouse effect.....as per Anya's info....then boomshangalang, away they go.

    I would like to know if the wind speed is constant or gusty? Are there weather fronts on Mars?
    How deep, yes deep....is the katabatic wind, and does this affect the fan making process?
    If it has been observed by other projects to shift around in a regular pattern? (which would tell us a lot....).
    How the material becomes infused within the sublimated gas, allowing itself to be belched forth-wouldnt it be heavy and frozen hard?
    Whether the material beneath the ice is very loose-(perhaps it is filtered into a fine dust by millenia of going up and out and back through the ice....?)

    Hmmmm....

    Posted

  • Paul_Johnson by Paul_Johnson in response to Paul Johnson's comment.

    I would love to know the duration between fan production at the same fan....that is critical to the whole piece!

    It tells you how long the cycle of gas expansion takes to become critical, no?

    Posted

  • Ian_Mason by Ian_Mason

    I wanted to out some of the comments from last night into a new
    thread, as the other one is mahhhoosive...

    Flippin heck Paul! I am not so sure this is such a small thread either, & it is only you that has posted until now! lol

    πŸ˜ƒ

    Posted

  • Paul_Johnson by Paul_Johnson

    What is tthe actual source of the gas? Is it in the soil and is perculating up? Is it the bottom of the dry ice sublimating as the sun passes over and heats through a greenhouse effect? Or is it just the natural gas that is present under the ice expanding with no way of release until the ice cracks and bang?

    Any ideas?

    Posted

  • Paul_Johnson by Paul_Johnson

    Ian, lol ! Sorry !

    Here's a nice pic to add to the melee! I am guessing that the lighter material went first, then some time later the darker stuff.

    APF0000qqk

    Posted

  • Paul_Johnson by Paul_Johnson

    Anya... 'we know that most of fans formed in early spring become brighter with time, so their apparent size decreases. But if the fan was created in second half of spring - it never shrinks.'

    Does the katabatic flow ifrom the pole into the spring season, then ease up as spring gets warmer....? Could the katabatic (which might be drier/different in chemical composition/significantly colder) affect the material to turn it white? Or maybe the materials are chemically different, as seen when some jets are blue, some brown from the same vent....maybe from different depths....?

    Posted

  • Kitharode by Kitharode moderator

    Whhrrr..tick..tick..bzzzz..click..-.. ready to assimilate new data..-..bzzz..tick..tick.........."Hello..tk..bzz..again..Paul"...........

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  • Ian_Mason by Ian_Mason

    Does CO2 gas react with anything, & cause an even more explosive pressure?

    I just picture CO2 gas building up under a huge sheet of ice & forcing itself deep down into the Martian soil, & then reacting with something else which in turn causes intense pressure, & kind of forces other neighbouring 'build ups' of gases to do likewise, & it like a chain reaction going off.

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  • Paul_Johnson by Paul_Johnson

    Good evening Kitharode, how are you sir?

    Posted

  • Paul_Johnson by Paul_Johnson

    Ian, I was wondering if it reacts with the iron in the soil, when it sublimates? creating something else that is more volatile than the very inert CO2, something that might expand with more oomph. Maybe there are other gaseous elements that are present that add to the mix.

    Posted

  • mschwamb by mschwamb scientist, translator in response to Paul Johnson's comment.

    I believe, because it's a gas under pressure trying to reach the atmosphere and goes the path of least resistance through the weakest parts of the ice., So I believe that's all that is needed. So the carbon dioxide gas is trying to escape kinda in the same way as if you shake a closed soda bottle and open it, the carbon dioxide in the soda isn't reacting with anything just entering into our atmosphere and creating the shooting geyser of soda.

    Hope that helps,

    ~Meg

    Posted

  • Paul_Johnson by Paul_Johnson

    Where does the gas originate from though Meg, what is its source? Is it just the natural gas in the surrounding air, or is it from the chemical reaction of the ice sublimating as the sun does its greenhouse thing through the ice?

    Maybe its both?

    Posted

  • Kitharode by Kitharode moderator

    Hi Paul. Hi Everybody. I'm well enough, but I could do with some sleep, and food, but they can wait. You say good evening; I thought it was morning!! Don't even know what day it is, my friend. I'm currently shifting my mind-set away from "revised Alypian tetrachordal modulations between related scales of the genera" and have come here for some light entertainment. Hi-Ho, it's a hard life πŸ˜ƒ

    Had a bit of a mini-google on solid state greenhouse effects (don't worry, it didn't hurt too much and the swelling has gone down) and although I didn't learn much, ie, I didn't understand most of it, there's an odd snippet that might be useful in 'the other place'.

    Great idea to create new thread and I hope you'll keep the title the same if you create a part 3, 4, 5 etc. A great way to organise the ongoing threads, keeps us ontrack, reminds us what we know and what we need to know. Part of the problem with the latter, I think, is the (understandable) need for the Science Team to run 'blind tests' with the images. In the end, although this is a collective effort, it is 'their' project and we must be patient with them. I've noticed an odd snippet that suggests there will be more 'openness' later, which might help.

    Ah, kettles just boiled. Here coffee coffee coffee......Keep up the good work. Speak later.

    Posted

  • wassock by wassock moderator

    Paul the gas comes from the ice - which is solid CO2 (dry ice or cardice at home) when the ice warms up it sublimes (goes straight from solid to gas) to produce gaseous CO2.
    Now anyone care to enlighten me on "katabatic wind" beyond "its a wind that blows down"?

    Posted

  • Paul_Johnson by Paul_Johnson

    I reckon it's colder air moving downhill from a higher point. Much colder than normal winds and very strong....think of those huge groups of frozen daddy pemguins huddling together in a fearce constant gale.....that's your Katabatic right there.....!

    Any viewes on the demise of the BBT, wassock? lol

    Posted

  • Paul_Johnson by Paul_Johnson

    Thanks buddy, the production of gaseous CO2 from the very bottom of the ice itself is very interesting, because there must be voids or pits there already for it to build up in, eh?

    Posted

  • mschwamb by mschwamb scientist, translator in response to Paul Johnson's comment.

    Yep as wassock said, there's an ice cap of semitransparent carbon dioxide ice and when the sun shines, it heats the bottom and sublimates the base into carbon dioxide gas that's initially trapped under the ice sheet trying to get out. ou can learn more about the geysers and how the fans and blotches form here and here.

    Cheers,

    ~Meg

    Posted

  • Kitharode by Kitharode moderator in response to wassock's comment.

    From Wikipedia. Obviously we are on Earth here:

    A katabatic wind, from the Greek word katabatikos meaning "going downhill", is the technical name for a drainage wind, a wind that carries high density air from a higher elevation down a slope under the force of gravity. Such winds are sometimes also called fall winds. Katabatic winds can rush down elevated slopes at hurricane speeds, but most are not that intense and many are on the order of 10 knots (18 km/h) or less.

    Not all downslope winds are katabatic. For instance, winds such as the Foehn, Chinook or Bergwind, are rain shadow winds where air driven upslope on the windward side of a mountain range drops its moisture and descends leeward drier and warmer. Examples of true katabatic winds include the Bora (or Bura) in the Adriatic, the Bohemian Wind or BΓΆhmwind in the Ore Mountains, the Mistral, the Santa Ana in southern California, the Tramontane and the Oroshi in Japan. Another example is "The Barber," an enhanced katabatic wind that blows over the town of Greymouth in New Zealand when there is a southeast flow over the South Island. It is a wind that is known in the area for its coldness.

    A katabatic wind originates from radiational cooling of air atop a plateau, a mountain, glacier, or even a hill. Since the density of air is inversely proportional to temperature, the air will flow downwards, warming adiabatically as it descends. The temperature of the wind depends on the temperature in the source region and the amount of descent. In the case of the Santa Ana, for example, the wind can (but does not always) become hot by the time it reaches sea level. In the case of Antarctica, by contrast, the wind is still intensely cold.

    The entire near-surface wind field over Antarctica is largely determined by the katabatic winds, particularly outside the summer season, except in coastal regions when storms may impose their own windfield.

    Katabatic winds are most commonly found blowing out from the large and elevated ice sheets of Antarctica and Greenland. The buildup of high density cold air over the ice sheets and the elevation of the ice sheets brings into play enormous gravitational energy. Where these winds are concentrated into restricted areas in the coastal valleys, the winds blow well over hurricane force.[1] In Greenland these winds are called Piteraq and are most intense whenever a low pressure area approaches the coast.

    In a few regions of continental Antarctica the snow is scoured away by the force of the katabatic winds, leading to "dry valleys" (or "Antarctic oasis") such as the McMurdo Dry Valleys. Since the katabatic winds are descending, they tend to have a low relative humidity which desiccates the region. Other regions may have a similar but lesser effect, leading to "blue ice" areas where the snow is removed and the surface ice evaporates, but is replenished by glacier flow from upstream.

    In the Fuegian Archipelago (or Tierra del Fuego) in South America as well as in Alaska, a wind known as a williwaw is a particular danger to harbouring vessels. Williwaws originate in the snow and ice fields of the coastal mountains, and while they commonly blow as high as 100 knots, 200-knot williwaws have been reported.

    Posted

  • Paul_Johnson by Paul_Johnson

    I joust read that the Mars Katabatic blows at 250mph! That must have a major impact on fan shape, distance etc, 250mph!

    That's a factor! Also, would easily (?) have an effect on ice flow across the surface, plugging any holes....

    Also, killing any Martian Penguins, poor things......

    Posted

  • Kitharode by Kitharode moderator in response to Paul Johnson's comment.

    250mph. On Earth that is well scary, but because the martian atmosphere is about 100 times 'thinner' than that of Earth, would it be as scary on Mars?

    Posted

  • Paul_Johnson by Paul_Johnson

    A third as dense, good point! I guess it would be like a wind of 80mph......a third. Really cool thinking Kitharode!

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  • wassock by wassock moderator

    OK got the gist of katabatic now - so where's the hill?

    Posted

  • Paul_Johnson by Paul_Johnson

    The south pole!

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  • wassock by wassock moderator

    Shurely that's at the bottom:-P

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  • Kitharode by Kitharode moderator in response to Paul Johnson's comment.

    Thanks. I wasn't sure if (atmospherically) thinner = less mass = less umph. Seems we agree it could.

    Where's the hill indeed? Need to check whether a hill is an absolute neccessity for creation of katabatic wind (on mars). I don't know the answer to that. If it's crucial, we need to find one - if it's crucial and there ain't no hill, maybe there ain't no katabatic effect. You might have blown your own theory (pun intended).

    Re the BBT. Is this your Big Bubble Theory? Which thread is it in - this one or 'the other place'?

    Posted

  • Paul_Johnson by Paul_Johnson

    Hill surely is a must!

    -I think the poles are higher than the surrounding land, like here on earth. I can't explain why, maybe something to do with the shape of the planet?

    Yes, the BBT has been burst, damn it ! We love that theory, it is pure citizen scientist gold, that one! I still haven't given up on it, to be honest.....its wassocks idea in the other place, and I still believe....well part of me does....

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  • Paul_Johnson by Paul_Johnson

    wassock.....south pole at the bottom....hmmmmm.

    Oh dear......!

    Posted

  • Paul_Johnson by Paul_Johnson

    Here's a thought, when the ice turns into this sublimated gas, which acts like a liquid, is the dark dusty material held in suspension within it?

    Or is it washed out from the surrounding area during the explosive decompression?

    Posted

  • Ian_Mason by Ian_Mason in response to Paul Johnson's comment.

    Thanks Paul,

    Looking at images containing so many identical shaped closely neighbouring fans, it is hard not to believe that many of these don't burst out within minutes or seconds of eachother, & not in some way connected to eachother.

    If that is the case, then I really am convinced it is a reaction with something else, & one outlet not being enough relief perhaps.

    I love viewing these images & trying to make sense of it all, but maybe nobody will ever know unless they send up a Rover with its winter woolies on, lol.

    πŸ˜ƒ

    Posted

  • Kitharode by Kitharode moderator

    Mars has an equatorial diameter of 4228.4 Miles and a polar diamater of 4197.2 Miles. A difference of about 31 miles.

    I've read somewhere on here that one pole is 'higher' than the other (can't remember which one, or by how much).

    Posted

  • wassock by wassock moderator

    OK the fluid bed theory - may need to take this one as a new thread if it flies, but I'm having trouble thinking those who've been at this a long time haven't been around this before. The dust in the fans is the surface of Mars. The escaping gas picks up the dust and drops it on top of the ice, eventually the ice melts and the dust returns to the planet surface. Thus the surface under the ice is covered in a layer of dust . For the time being lets ignore and wind during the summer which may blow our dust away and jump forward to next Spring when we have a meter of fairly see through ice on top of a layer of frozen dust. The sun rises and shines through the ice onto the surface beneath which warms up. The overlaying ice acts as a blanket keeping the heat in at the surface and so the the whole surface beneath the ice begins to warm up. Eventually the surface gets warm enough for the solid CO2 to turn to gas. As the surface is dust it also contains CO2 frozen there at the outset of winter. So we get gas coming from the bottom of the ice and out of the underlying dust layer. Now we have a layer of warming gas dust mixture which will continue to sublime gas from both ice and dust, this process is going on over the whole ice sheet and as we are looking at an area of fairly flat terrain, featureless apart from a few scattered boulders, the whole of the surface/ice interface is one large layer of gas/particulate. Pause for breath

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  • wassock by wassock moderator

    All the time the ice within the dust is melting the volume available for the gas keeps increasing but eventually the melting of the CO2 reaches the bottom of the dust layer and the pressure begins to build. Now if you recall those random scattered boulders they've also been basking in the sunshine all the while, warming up and melting the ice around them until it gets thin enough for the pressurised gas to force its way out. I suspect there are more than one mechanism for 'popping the cork' but I think this one is the easiest to both describe and understand (even if it's nothing like the truth). As all the boulders are fairly uniform in size and are subject to the same amount of solar gain and sit in a fairly even thickness of ice they all 'pop' at more or less the same time and produce fans which are all aligned with the wind direction at the time. Because the bottom of each boulder sits in the layer of gas/dust which covers the whole area they all are drawing from the same supply, consequently any boulders which are slightly bigger or darker will warm up quicker and erupt for longer before the gas runs out, giving a bigger fan.

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  • Kitharode by Kitharode moderator

    Boulders come under the 'interesting features' umbrella of the project as far as I know. The possibility that they may be a 'trigger' for emissions, I think I'm right in saying, is one of the things the science team are working on.

    One things for sure - we're all learning plenty.

    Posted

  • Paul_Johnson by Paul_Johnson

    wassock, take a bow!

    What a great way to put it together like this, truly amazing.

    I gotta go now, but you just made my day.

    FANtastic!

    Posted

  • wassock by wassock moderator

    Night falls the areas of ice exposed to air freeze up again sealing the boulder vents as there's no longer any gas pressure to keep them open. And the process starts again, only this time there's less dust beneath the ice leaving more room for a bigger build up as gas (maybe?) Next time the eruptions happen the relative proportions of the boulders is still the same so we get the same order of 'pop' as before so the relative duration of the eruption for each hole stays the same as before giving rise the secondary fans in the same proportions between fans as for the first time. The spiders get formed because any slight variations in surface levels will mean that the gas will find it easier to flow through a wide space under the ice and as whats flowing is a suspension of particles it will abrade the underlying surface making the gap a bit bigger for the next time. Do the spiders a fill with dust during the summer I wonder?

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  • Paul_Johnson by Paul_Johnson

    wassock, you are on a roll buddy!

    Posted

  • wassock by wassock moderator

    OK now to go really out on a limb, I floated this one earlier in a thread I've not been able to find so not check for any feedback to tell me it's rubbish because.... However - There are noticable round features associated with some of the fans/blotches. The idea that a boulder in the ice would cause preferential melting around it seems sound. BUT for my idea to work as an explanation for the V/heart shaped fans I think I need them all to erupt at more or less the same time. This means that I need all the 'boulders' to have very similar thermal properties which boils down to being the same size. Once we have a surface feature which catches the sun it seems reasonable that it will do the same thing year after year so long as it doesn't move. I may only be a pebble to start with and at that size only produce a vent when the ice is thin at the end of the season. But where we have a vent we have a pressurised gas/solid mixture moving from state of high pressure to a low pressure one and doing this repeatedly year after year at the same spot.. On earth places where high pressure stuff changes to low pressure are often places where we see deposition forming structures around the vent. Here surface of the vent is the pebble in the middle and so if it were possible that this system could some how leave something behind as it decompresses then it would make since it the pebble slowly got bigger. So there you have it the boulders are stalagmites which all grow at a fairly constant rate (for some reason I can't think of) making them all the same size(ish). Course my other theory is that dinosaurs are very thin at one end................................

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  • Kitharode by Kitharode moderator in response to wassock's comment.

    From your preceding, and brilliantly constructed, earlier post - "The escaping gas picks up the dust and drops it on top of the ice, eventually the ice melts and the dust returns to the surface. Thus the surface under the ice is covered in a layer of dust, once the ice is 'reformed' (?)(the word is missing in your post, but I understand what's being said.

    Might we infer from this that a 'stain' of darker material will form under the ice, which will become a 'hotspot' in the following season, leading to new eruptions at, or near, the previous seasons 'emission point'?

    Posted

  • wassock by wassock moderator in response to Kitharode's comment.

    Think that its ...covered in a layer of dust. full stop, don't need the extra bit, making this up pretty much as I go along so think a bit of random musing got in there. I wondered about what the ice free surface would look like, covered in dry fans and so on. But I suspect that the dust in the plumes is actually going to be fairly fine and will get blown all over the shop next time the wind blows.

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  • wassock by wassock moderator in response to Kitharode's comment.

    OK if we buy the layer of dust/gas being involved in the melt then we also have a mechanism to give us big dark fans and smaller diffuse ones - Thick layer of surface dust = big fans, thin layer - small fans (and there's some really tiny ones out there. Think the subtle change I'm introducing here is the idea that the dust is not just what the escaping gas bashes off the underlying rocks, as implied in the turtorial and FAQ's but rather whats laying on the surface already before the ice forms.

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  • Kitharode by Kitharode moderator

    Sorry wassock. I'm losing it. I don't understand your thick=big, thin=small idea.

    I get the impression that your second sentence is a chicken and egg situation, or it says the same thing in two different ways.

    As I said, I'm losing it a bit here so don't let me stop your flow. At the same time, explaining something more than once is often useful.

    Posted

  • wassock by wassock moderator in response to Kitharode's comment.

    If the ice sits on top of solid rock then theres not much room for the gas to occupy so you dont get a big fan, the only space available is whats created as the ice sublimes but gas needs more space than solid so its all a bit tight. If a layer of dust underneath then its easier, somehow, to make gas. Either wa its dust that makes fans, so if theres a thick layer of dust you get a dark fan with lots of dust. If tgeres no dust there already the fan is jade of just what the moving gas erodes and has less material in it

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  • Paul_Johnson by Paul_Johnson

    I'm with you wassock, and there are fans that seem to have erupted but not thrown much material at all out-are you saying these would be from a rocky surface under the ice. And bigger fans develop from areas that are very loose and dusty, which allows more gas to build up underneath....?

    Me brain hurts!

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  • Paul_Johnson by Paul_Johnson

    wassock, I wish I could find the comments I made 2 days ago on some geezers picture, referring to boulders, where I call them stalagmites, that have built up over time, eruption after eruption. I don't really hold with the boulder sinks into the ice theory, surely any heated material on such a boulder would simply sublime and move away??? They can't be very conductive either-its ice! I thought that the fans would come first, then the boulders would form at the opening, which is a slightly different conclusion to yours....my boulders are all deposits after the event has happened, well during it anyway. I think once the fan has created such a boulder, it may grow and grow (like a martian pearl) in the fierce katabatic wind, which would be continually depositing new material on it...!!!!

    It must be worth exploring????

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  • Paul_Johnson by Paul_Johnson

    If the boulder is an existing rock (which I think the scientists are saying....) why does it elevate itself upwards to sit on top of the CO2 ice-no, I'm not having that! The ice would form over and around it. There are also many images of these ice boulders in lines, along faults in the ice. I suppose the question is, which comes first, the ice egg boulder or the fan chicken?

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  • Kitharode by Kitharode moderator

    OK, let's see if I've got that. Are you saying that a layer of ice on top of 'solid rock' surface, ie, 'dust-free', leaves little room at the interface for large volumes of gas, therefore any emission points have only a minimal amount of material to eject, ergo minimal fans? Conversely, other ice layers sit on top of deep layers of dust where the volume available for gas storage is much greater (the greater the depth of dust, the greater the air spaces), ergo emission points have loads of material to eject? If you are saying that, I'd go along with the idea for now - pretty sound theory, lots of visual 'evidence', good logic - yep, it's a runner.

    Re the boulders. You'll be aware of the 'wire through a block of ice trick' I'm sure. Huge block of ice, weighted wire draped over it, wire eventually cuts through ice block (sealing its path behind it). Primarily due to gravity. Yes, gravity on Mars less than on Earth but boulders much more massive than wire. Not sure if that goes anywhere, or relates in any way, but there again......

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  • Paul_Johnson by Paul_Johnson

    Yes, Kitharode.....but how does the rock get on top of the ice in the first place? And why isnt it being cooled by a 250mph katabatic wind. If it is a solid rock boulder the ice wouldnt lift it up, it would settle on top and around it.....it couldnt then melt back down through any ice deposit......or could it...?

    I have never been in love with the Hot Potato Theory, I think the boulders are ice stalagmites, formed by the act of eruption and added to by the very much colder katabatic.....I sort of know this is the opposite of scientific thinking, but hey, I'm a stubborn so and so, and don't get the HPT.

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  • Kitharode by Kitharode moderator

    I've read your stalagmite thread, but I too can't find it again. I really like the idea - it's bold and very intrigueing. It sounds at least possible, even plausible, but it lacks something. I can't say what precisely, but I think you should keep the idea alive and work towards proving or disproving it. Occam's Razor is not always correct in what it slices away. (You know Occam's statement? - When confronted with two competing theories, the more simple of the two theories is probably correct). Currently, boulders are the best/easiest bet, hence the interest in them. Can you strengthen your case? I hope so.

    If we're talking boulders, I don't know where they're coming from initially. A couple of vague possibilities spring to mind, but basically I don't know - needs discussion. Leaving that aside, scientists are trying to work out if these alleged boulders might 'act as a trigger for emission events' (my words, not theirs). For now, let's say they are right. Boulder arrives, or appears, pulls trigger, venting of stuff, area depresses (forms channels, makes spiders), cycle repeats, boulder sinks, eventually buried/eroded?, cyclic venting continues without boulder because depressed channel more suseptable to venting.

    If this were the case, we would expect to find; boulders no fans, boulders with fans, smaller/less visible boulders with fans, eventually leading to - fans no boulders. All these scenarios can be found in the images. End of waffle - your turn.

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  • Paul_Johnson by Paul_Johnson

    Well, I want to know how the boulders get up there! (stamps feet and cries).....

    Yes, plenty of fans with boulders and without boulders, plenty of boulders without fans!

    Incidently, would the presence of a boulder above it affect the pattern of a fan, you know, blasting upwards into the boulderinto the wind? Just a thought.....I think that is a different thread......standby......

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  • wassock by wassock moderator

    I don't think anyone is saying the boulders are on top of the ice, if its a big one then it might peep out of the top and the warming effect would probably be bigger. But either way you have something within the ice which can warm up in the sunshine

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  • wassock by wassock moderator in response to Kitharode's comment.

    The stalagmite post is top of page 5 in this thread

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  • wassock by wassock moderator in response to Kitharode's comment.

    I was nudged to the stalagmite hypothesis by 2 things one is a science team comment on a image with several very bright 'boulders' on it. They were saying they couldn't figure were the things had come from and the other was a post, probably the one Pauls referencing, were some one asked if they could be stalagmites - and I thought hey why not. I think the key points to get straight before saying yup theres an outside chance that "this could be it" are; 1 do the fans/blotches appear around the same features every year 2 we need a mechanism for deposition at the vent point. Very much not my department there but it seems to me that back home there are lots of places where stuff (ok liquids admittedly) vent from high pressure to low we see things forming, like the chimneys in the mid ocean ridges. I can see a reason why you'd get a pillar instead of a chimney in this instance but that's no good if it can't happen any way. On another tack Science Team - has any one built themselves a low pressure wind tunnel and played around with some talcum powder yet?

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  • Kitharode by Kitharode moderator

    Do you know about sailing stones? You need to watch this: http://www.youtube.com/watch?v=u1hoiHvOeGc

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  • Kitharode by Kitharode moderator

    I guess when we talk about things like this, we must bear in mind that we are using an astronomical / geological timepiece, rather than a pocket watch....

    Wikipedia - In places covered by ice sheets during Ice Ages, such as Scandinavia, northern North America, and Russia, glacial erratics are common. Erratics are boulders picked up by the ice sheet during its advance, and deposited during its retreat. They are called "erratic" because they typically are of a different rock type than the bedrock on which they are deposited. One of them is used as the pedestal of the Bronze Horseman in Saint Petersburg, Russia.

    Some noted rock formations involve giant boulders exposed by erosion, such as the Devil's Marbles in Australia's Northern Territory, the Horeke basalts in New Zealand, where an entire valley contains only boulders, and The Baths on the island of Virgin Gorda in the British Virgin Islands.

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  • Kitharode by Kitharode moderator

    With two threads on the go (and threats of a third in the background) I'm worried I might be taking the boulder thread too far here, moving you away from your more specific aims (if you still have them). Guys, let me know whether to keep adding 'boulder chat' here or not.

    Likewise, I'm thinking of starting a new thread, related to, but different from Killers 1 & 2. The first entry (if I get it together) could be quite long and it would need composing, so I'd write it up before posting. I'd really, really like to call it "Killer Rays (3) - Revenge of the Slabs" but I thought it polite to ask. (I like polite as much as I like humour and 'deep thought'. That's why I'm still here with you πŸ˜ƒ

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  • wassock by wassock moderator

    Kitharode - Pauls just put up a new boulder thread! I thought of the erratics when I saw the post about the boulders with no obvious source, the comment about them also mentioned that they hadn't moved since first observed even though they're on a slope

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  • wassock by wassock moderator

    NB the agglestone in Dorset is an isolated 400 tone lump of sand stone in the midst of coastal heathland - the area hasn't been glaciated!

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  • Kitharode by Kitharode moderator

    Thought this might be useful. Not sure which thread it belongs in (relevant to all probably). It's by Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay

    "The atmospheric pressure on Mars is just a bit below the triple-point pressure. That's why the textbooks all say liquid water is unstable on the surface of Mars. Any liquid water will rapidly evaporate and the rest, cooled by evaporation, will freeze. Low spots on Mars may have pressures above the triple-point pressure, but are usually far too cold. Even if you did somehow get above 0 C on Mars and into the liquid field, you're so close to the vapor curve that water would rapidly evaporate. Even solid ice would quickly sublimate on Mars except in the very coldest areas. Unlike other planets where zero elevation is the average radius of the body, on Mars, zero is the altitude of triple point pressure."

    I'm particularly interested in the final sentance. I get the feeling that if we get a clear picture of what it says, we may be able to say something meaningful about the relative altitude of objects. Or again, perhaps clutching at straws. Good info though, eh?

    Mars Polar radius; 3376.2 km
    Nasa fact sheet; http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html

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  • wassock by wassock moderator

    The triple point for a substance is a unique combination of temperature and pressure at which any of the 3 phases can exist at the same time. So solid can go straight to liquid or gas, gas to liquid or solid, liquid to solid or gas, move away from this point by warming it up and you have to go solid to liquid to gas, make it colder or reduce the pressure and theres just solid or gas allowed. For water the triple point is at about 0 celcius and1erarth atmosphere pressure. On mars the pressure is nowhere near that so you cant get liquid water, what ever the temperature. Triple point for CO2 is at a lower T and P but the triple point pressure is still higher than on mars so no liquid allowed there either

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  • Kitharode by Kitharode moderator

    Thanks wassock, that's useful. Although I've met these terms before (STP, triple point, etc) at Uni., it's a good while ago and physics was definately not my best subject πŸ˜‰ I'm gonna start a new thread on this so we don't clog this one up. Cheers.

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