Planet Four Talk

Ask a Team Scientist

  • Portyankina by Portyankina scientist

    I think, I'll make a separate topic where anybody can ask me questions directly.

    I hope you enjoy the discussions in the forum! I would like to follow up on all of them, but I am time-shifted to most of you, so it's not that easy. At the time, when I have a moment to have a look at the forum some of the discussions are buried under new ones and some get so long, I never can get through them! And it's even kind of useless because often you find solutions/explanation on your own and I simply lose time reading through them.

    So, if you have an open question at the end of the day, ask me here!

    I will have a look in this post at least once a week and answer as much as possible. Please, do not create discussions in this topic! It will kill its idea.

    Thanks and good work and lots of fun to everybody!

    Anya

    Posted

  • Paul_Johnson by Paul_Johnson

    Hello Anya, could you please clarify something for me?

    Do boulders poke through the CO2 ice and weaken it-or are they on top of the ice and sink down-in which case, how do they get on top?

    Cheers Anya....I'm still confused.com!

    Posted

  • wassock by wassock moderator

    Hi is there any milage in the idea that some boulders are depositation or accretion features? I've floated this in these threads http://talk.planetfour.org/#/boards/BPF0000002/discussions/DPF00007op and here http://talk.planetfour.org/#/boards/BPF0000002/discussions/DPF00007z5 but as you say the stuff gets buried in when the number of posts gets large and these 2 both took off. OK the idea is that we've got gas containing dust passing regularly past the same point (a boulder) over a very long time span. The gas is moving from high(er) pressure to low and the situation may lend itself to some interesting chemistry and if the pressure differential is sufficient there ought to be some phase changes for some of the constituents of the gas (however fleeting) Some of which will be normal atmosphere traped in the surface dust at the outset of winter.. A very cursory looksee shows there are some reference to reducing reactions between CO2 and Ferrous oxide but mainly in relation to theoretical ways of turning CO2 into rocket fuel. So has this been looked at as a possibility and ruled out, a new idea (I doubt it) or is it just fantasy?

    Posted

  • Wounded_Knee by Wounded_Knee

    The only fuel that could be possible to use in these conditions is possibly Hydrazine, CO2 an ferrous oxide at these temp an pressure will result in not a lot.....alledgedly 😃........................................edit..http://en.wikipedia.org/wiki/Rocket_propellant

    Posted

  • jellyhead by jellyhead

    Hello, just wondering whether you could say more about the 'cleaning model' that Michael mentions in APF0000hkc? I've been fascinated by the spiders and how they form and the white patches in this image appear to be the start of the spider cores. Do you know whether the features in APF0000j9e are the same type of terrain, but without the ice sheet? I've also been wondering whether the formation of the spider channels is more about where CO2 gas cannot escape to the surface rather than from where it can. So small gas patches form under the ice sheet, maybe due to hotspots from the sun, ice sheet thinning or around an impurity or channel from the previous year and because the gas can't escape through the ice it forces its way through the dust/weaknesses in the bedrock - in the spider's case radiating outwards from the central patch. Are you able to say whether the spider's grow gradually each year, or whether they just appear pretty much fully formed? Thank you!

    Posted

  • Portyankina by Portyankina scientist in response to Paul Johnson's comment.

    Hi Paul!

    Boulders are kind of inside the CO2 ice: mostly they poke through it but some CO2 is deposited on top of boulders. Tat part goes away the fastest. They surely do weaken the ice.

    Anya

    Posted

  • Portyankina by Portyankina scientist in response to wassock's comment.

    Hi,

    I am totally not a chemist, so you have to get more precise with me on this. What reaction do you now mean? Every reaction between CO2 and any of iron oxide(s) that I have seen so far requires high temperatures, like 700K high... So could have not happen here.

    Anya

    Posted

  • Portyankina by Portyankina scientist in response to jellyhead's comment.

    To jellyhead:

    I am a bit confused with your images and what you are asking about them. First image has bright tiny spiders, maybe very young ones. Second image has well developed spiders and it is covered by CO2 ice layer.
    We do not see spiders change in any way, not growing not eroding; we believe that they grow gradually but the changes are expected to be too small to be noticeable in 3 years that we have HiRISE data for. The estimation of the time needed to create large spider is of 10^5 years.
    The erosion happens all the way along gas passage. So if gas travels towards the central vent from the very end of the spider arm, it will erode all the arm.
    Did this answer your questions?

    Anya

    Posted

  • jellyhead by jellyhead in response to Portyankina's comment.

    Thank you so much, yes it does answer my questions - I completely misinterpreted the second image! I still don't understand how the spider's distinctive shape originated if the erosion happens as gas travels towards a central vent - the channels must already have to be there for the gas to 'choose' that route. Will reread the blogs and see if I can get my head round it!

    Posted

  • Chocstar by Chocstar

    Hi Anya, roughly when were these first season of images captured ?
    When is the next phase/season of images going to be released for viewing and classification ? Just curious.

    Posted

  • Kitharode by Kitharode moderator

    Spider Classification Scheme (SCS). I'm typing up my ideas for SCS, but it might be lengthy, so no posting here. I'm happy to start new discussion, but I wondered if you wanted 'eyes first', so I'm not treading on toes/getting out of hand. Hopefully ready tomorrow, so will await your instruction.

    Late addition. SCS typed and ready for your consideration. It goes where .. ?

    Posted

  • wassock by wassock moderator

    There are teeny weeny spiders and great big fat ones and all sorts in between, there are also areas without spiders which do have fans and blotches. If the theory of spider formation holds then anywhere that a vent occurs the beneath the ice there should be a spider forming. So why are there different 'generations' of spiders ? Does a 'flat' landscape showing only vents without any noticeable spiders, or only tiny ones, imply that the surface has only recently been ice bound in the winter or that the surface is 'new'? (or that vents have only recently started to form in the area) I'll put this up as a separate thread as well to save this thread from getting choked

    Posted

  • Paul_Johnson by Paul_Johnson

    From what I can gather, it's a time thing wassock....! The grow fatter just as they get older, like us.

    Posted

  • Kitharode by Kitharode moderator

    On Mars, zero altitude is the triple-point (tp). (Relax, I'm discussing tp elsewhere). On other rocky bodies, zero altitude is the average radius of that body. Can you tell my why the tp was chosen in favour of average radius? Or, perhaps post a link where I can read about that question. Ta.

    PS. Wassocks spider question has gone elsewhere. (Saves you a job).

    Posted

  • Portyankina by Portyankina scientist in response to Chocstar's comment.

    The first season was in 2007, we are now in our 4th southern spring imaging campaign. In the classification that you are doing are 2 first years. We still are to release to you, guys, 3rd spring. That's part of my job:I have to go through the images to sort the poor quality ones out... I promise, the good ones will come soon, hopefully next week.

    Anya

    Posted

  • Portyankina by Portyankina scientist in response to Kitharode's comment.

    to Kitharode 1:

    I'm gonna scan forum for your Spider Classification Scheme (SCS), but do not hesitate next time to put a link in here 😃

    to Kitharode 2:

    Not sure, why the TP was chosen, it sounds very arbitrary to me. Mars has huge difference in altitudes between Olympus and Hellas basin, I guess, it's not that important how you define where zero is, just as long as it is between the highest and the lowest.

    Anya

    Posted

  • Portyankina by Portyankina scientist in response to wassock's comment.

    to Wassock:

    I don't know what you came up with on your question, but I'll answer you here, what I think about it:

    There is several parameters that rule how easy is to carve a spider:

    1. the top surface "erodability" - how easy it is to rip off chunks of material from the surface.

    2. exposure time - how long the surface was exposed to the erosive forces. For example, if some areas were covered by the "permanent" polar cap that is gone now.

    3. erosion efficiency - how heavy is each years' erosion evet, this will depend on the amount of energy area gets, thickness of the seasonal ice layer, maybe confinement of jets, things like this.

    So, you are solving multi-parameters problem if you want to answer the question why some areas have spiders and others don't. We wanted to do it with statistics, because so far nobody came up with the clear idea, why spiders are not everywhere in the polar areas.

    Anya

    Posted

  • Kitharode by Kitharode moderator

    (SCS) posted here. http://talk.planetfour.org/#/boards/BPF0000002/discussions/DPF00009es

    I'm up for an hour or two so.........

    Posted

  • Portyankina by Portyankina scientist in response to Kitharode's comment.

    Well done! And see my comment in that thread.

    Anya

    Posted

  • jellyhead by jellyhead

    Hi Anya. Is there an explanation anywhere on how spider's actually begin? I can see them developing fine once they get started but how do they get started and why do they radiate outward/inwards to a central point, why not random joining of channels? If we know what it is that 'initiates' the spider growing process, does this tell us something about why they can't get started everywhere?

    (Posted in the 'why are spiders not everywhere thread' as well)

    Posted

  • wassock by wassock moderator

    As a companion to jellyheads question I have been musing something similar - how does a spider grow a new leg? The answers to both seem obvious to me so would like to see what the partyline is from your end before I show you any egg sucking

    Posted

  • Portyankina by Portyankina scientist in response to jellyhead's comment.

    If we take the hypothesis that spiders are carved by sub-glacial gas flow, than we can as a starting point consider the flow towards a vent, say, from a circle area. From hydrodynamics we know that the flow does not stay uniform - more dense streams inside the flow emerge. It happens even in idealistic conditions (like flat smooth ground surface with a flat ice layer), let alone realistic landscape. More erosion will happen where the flow is stronger (i.e. denser, faster, etc.) - most probably close to the exit vent. This is how you start the spider.

    The development of dendritic pattern is described by combination of deterministic and probabilistic processes, similar to river-bed development (for example), spiders even look like micro-version of these. The deterministic process here is the gas flow and probabilistic is erosion: say, presence of a flow does not mean that particular part of ground will be washed away - there is a probability term that rules if this will happen at some time period.

    Anya

    Posted

  • Portyankina by Portyankina scientist in response to jellyhead's comment.

    The new leg develops when the probability field for erosion is modified by singular event. In other words, when along the channel some piece of channel "wall" gets eroded away (there is always a probability that this happens!) and it falls off in such a manner that corners around it are easier to erode than the remote part of the channel wall. The probability to erode around this location becomes higher and this place develops to the new junction. To develop highly branched dendrite takes special probability field properties (read, erosion "map" of the surface) - we are in the very beginning of understanding this.

    Anya

    Posted

  • Kitharode by Kitharode moderator

    Update on SCS project: Short positive replies: My feedback/discussion: Breaking News item: and a Mk.II model on show.

    As and when you get there, I'd be interested to hear (if you can tell us) a little more about your SCS project. When might it start? Are you hoping for anything in particular, or have expectations? Will you try to develop the SCS on a more 'formal' level, Planet Four only level, schools/home-ed level?

    http://talk.planetfour.org/#/boards/BPF0000002/discussions/DPF00009es Cheers.

    PS: Coming soon - Preamble and 'generic' species images. I'll update you here.

    Posted

  • wassock by wassock moderator

    I'm thinking that there ought to be some cooling going on as the gas vents, so for a boulder vent at least you have a very cold lump of rock at the end which will help to seal the hole. I also have a ghost of a memory about the joule thomson effect and there being an inversion temperature so for hydrogen and helium even at warmer mars temps expanding them would warm them up. Gas particulat systems can do odd things, has anyone looked at the physics of the stuff coming out of the vents? I am sure they have, is there anything interesting there!

    Posted

  • wassock by wassock moderator

    Hi Anya A couple of questions following on from your blog post on tramlines/yardangs

    1, can you just confirm that the narrow dark lines are the ridges? and

    2 do you have an explanation for the very fine pathways that can be seen on virtually all the images of this type of terrain - APF000094m there are several here one runs top to bottom past the top most fan which it skirts the very edge of which I'm thinking rules it out as being a crack

    Posted

  • Kitharode by Kitharode moderator

    SCS: 'Generic' spider Images now on thread: http://talk.planetfour.org/#/boards/BPF0000002/discussions/DPF00009es?page=2&comment_id=510071ebdea653362a000008

    And a yes/no answer will do for this: Although I do mark some fans, blotches and features (honest!!) I've got to admit I'm more of a collector at the moment. This means I will often skip through several (many) images without marking anything. I'm not screwing anything up for you science teamsters am I - or am I?

    Posted

  • Portyankina by Portyankina scientist in response to wassock's comment.

    Hi!

    Yes, we did look into the gas physics of a jet. Had to numerically model it, here is the publication about it. The main result: nothing happens much in steady-state setting. Gas expands, cools slightly adiabatically, but not enough to produce snow. We are able to discribe the dust fans of smaller size. Explosive model is under construction to explain the large ones.

    For yardangs: yes, long vertical lines (gray-ish on the image you refer to) are ridges. Thin lines are cracks in the ice, I assume. Why that it passes through the fan (or rather fan lies over the crack) rules it out from being cracks?

    Anya

    Posted

  • Portyankina by Portyankina scientist in response to Kitharode's comment.

    Kitharode,

    Thank for the update! I am asking the team how they feel about using your scheme for the classifier tool. Let's see what they say.

    For your question, I'm afraid you are messing things up. We'll have each image looked at several times and we'll estimate which of marked fans (and their areas) are the true ones by comparing different people's marking. When you looked on the image and did not mark something that was there, you kind of gave that thing less priority - our algorithm will think, maybe other people did mistake and devalue their markings.

    Anya

    Posted

  • Kitharode by Kitharode moderator

    Sincere Apologies. I'm glad I asked. Will cease and desist immediately (but continue to mark images). I'll also pass this info along should I meet any other (soon to be ex-) collectors. Again, my apologies.

    Posted

  • Ian_Mason by Ian_Mason

    Hi Anya,

    Do you have any info on the likelihood of finding evidence of any failed/lost Mars landers in the area provided with these images?

    Sorry to detract from the talk of fan/blotch marking, but part of the addiction for me is to find some quite unique feature, or evidence of a lost lander on the next image shown. Mars Mission list

    Many thanks.

    Ian.

    Posted

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

    The fine lines look pretty much like hairs on the lens, they are wavey and a single line can extend (often/usually) across the image and beyond, they don't look like cracks more like animal tracks in an Ariel shot of the earth. The path I mentioned passes very close to a vent, if it were a crack surely we should be seeing some sort of fan coming from it?

    Your paper deals with an open vent with continual (during the day) out gassing. That works for me for the very dark broad fans which seem to me to be the result of regular (or constant) emissions while the wind direction varies within a fairly defined range of directions. But it seems to me that the fans which are made up of separate fairly narrow fans in several directions speak of a series of discrete, time separated events, which I guess is where the explosive side of the physics would come in.

    If there are 2, or more, types of venting this could also form part of the reason for the varying morphology of spiders. A constantly outgassing system will have lower pressures and velocities than a system where pressure builds before being released. Lower speeds will mean less turbulence and therefore less particulate being carried making these gas flow less abrasive than those from an pressurised system.

    Posted

  • Portyankina by Portyankina scientist in response to Ian Mason's comment.

    Hi Ian,

    Indeed, among the images we put in here are images of a campaign that HiRISE team conducted in hope to find the lost Polar Lander. I am not sure how many of those images made it to the final set, but they fit our criterias of having fans and/or spiders, so some must be here. The team never found anything, I must say, the question is still open.

    Anya

    Posted

  • Portyankina by Portyankina scientist in response to wassock's comment.

    To the first point: only if there is enough free material to make the fan. If the top surface of yardangs is hard and hardly erodible and there is few dust - we'd se no contrast of clean gas fan.

    And to the second: fully agree.

    Posted

  • Ian_Mason by Ian_Mason in response to Portyankina's comment.

    Thanks for the reply Anya, it is much appreciated. 😃

    Posted

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

    Thought the key feature of the terrain which allows the yardangs to form is that its loosely bound and homogeneous?

    Posted

  • wassock by wassock moderator

    Hi Anya can you say if there is ice in these images? http://talk.planetfour.org/#/boards/BPF0000002/discussions/DPF0000a3h APF0000hgt
    If there's not then we seem to be looking at an area where there were previous 'fans from cracks' a la APF00005r0 with the surface dust starting to fade into the background

    Posted

  • Kitharode by Kitharode moderator

    I could make use of some very general information about wind strength and duration if you have it, or maybe point me to somewhere I can find it. Eg., more in summer than winter (or vice versa); wind strength can be this or that much in winter, whereas in summer.... and so on. As I said, just general stuff. It'd be most helpful. Ta.

    Posted

  • michaelaye by michaelaye scientist

    Kitharode, you hit a sore point there, and a major motivation for this project! 😉 The general martian global climate simulations predict wind speeds and direction, but we know from other measurements that the wind speeds are predicted wrongly (too slow, if I remember correctly). So, your work will actually provide some real distributed input into martian polar wind speed and direction data! Thanks very much! 😉

    Posted

  • wassock by wassock moderator

    Was just about to post that wind info was part of the plan. Just out of interest how will you get a wind speed from the fan data when you don't know pressure of the gas beneath the ice, the size of the vent, the particulate size profile for each fan or the ppm of the particle/gas mix?

    Posted

  • Kitharode by Kitharode moderator

    In need of a 3-minute smile? http://talk.planetfour.org/#/boards/BPF0000006/discussions/DPF0000a93

    A gentle start for any younger readers, but it quickly gets into some real science. Hope you'll pass it around the science team - there must be one of you out there with a sense of humour!! Enjoy 😃

    Posted

  • Portyankina by Portyankina scientist in response to wassock's comment.

    We definitely will not be able to pin it down to the number without knowing all those parameters you mentioned. But we hope to get some kind of estimate: we can see with a model which parameters are most influential and to what degree.

    Posted

  • Portyankina by Portyankina scientist in response to wassock's comment.

    Yes, there is ice on the image APF0000hgt but it's thin layer only and maybe mostly H2O on top of the layer.

    Anya

    Posted

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

    Is that a thin layer melting or forming? Late or early season Water ice?

    Posted

  • wassock by wassock moderator

    Anya, Could you clarify what the surface beneath the CO2 ice is like (in general) I'm getting the picture that where it's not just bare rock we are looking at a dust layer held together by a permafrost with a mixture of water and CO2 ice in it. The CO2 component susceptible to seasonal sublimation, the H2O less so? And the ejected dust that which the sublimated CO2 releases from the inground ice.

    Posted

  • Portyankina by Portyankina scientist in response to wassock's comment.

    I am sorry for long absence, say, I was "out of town"...
    For your 13-day old question: there is really few water, the layer is at most tens of microns thick. It's "left behind" molecules that were trapped in the bulk of CO2 and collected ontop of it, when CO2 sublimes.

    For the sub-ice surface: it's regolith with water ice inclusions and some more uniform ice component below some "more desiccated" layer. Thickness of this layer changes depending on location with topography being the most important parameter to change it. CO2 ice does not stay in the ground, as in summer it heats up quite above the sublimation temperature. Water does have the seasonal variability on the top of the surface and in the atmosphere, but below protective regolith (and dust) layer it stays stable for thousands of years. The seasonal changes come later for water than CO2 because the temperature of sublimation for it is higher.

    Anya

    Posted

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

    But if we have a surface layer of dust then it is porous to atmosphere so when the surface freezes then so will the dust layer meaning that there will be CO2 ice in the dust. If the dust freezes before the surface 'seals' then all the available space between the dust particles will be CO2 ice. If the dust freezes after the surface ice seals it there will be an effective vacuum going on as the frozen CO2 takes up less space than the gas. Either way the fate of the CO2 in the dust must be a factor in how the spiders form.

    Posted

  • wassock by wassock moderator

    Just to restate this the spaces between the surface dust particles (regolith = fairly consistent size particles?) and as the atmosphere is largely CO2 there will be CO2 in amongst the dust all the time and it will freeze in situ come winter time. What sort of particle size are we looking at - big bits will have more space for gas and this will also effect gas formation come the spring. - large dark dust with a lot of frozen CO2 around it will produce lots of gas quicker than very small light coloured dust without much in the way of entrained gas?

    Posted

  • Portyankina by Portyankina scientist

    This is not that simple. The top surface varies from location to location and you should not forget that there is also water ice under a thin layer of regolith. But exactly such difference might explain why some locations are more active than others.

    Posted

  • AUricle by AUricle in response to Portyankina's comment.

    Anya,

    Have you considered the possibility that under the right pressure, the CO2 in the channels may be flowing liquid instead of gas?
    If this were the case, wouldn't liquid be more erosive (acting more quickly on the regolith) and shortening the time span considered necessary to form spiders...or any other channel features as well?

    Posted

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

    Trouble is you need 5 (earth) atmospheres of pressure to get liquid water, any less pressure than that and it can only exist as gas or solid. If you dive in the sea then every 10 meters you go down equals about 1 atmosphere additional pressure, 50 meters of water pressing down gives 5 atmospheres of pressure. Solid CO2 is about 50% denser than liquid so in round numbers 30 meters of CO2 ice will exert about 5 atmospheres of pressure on whatever it's sitting on - ON EARTH - gravity on Mars is 38% of Earth
    So in an ideal situation like a syringe in order to contain a pressure sufficient to get liquid CO2 the (standing upright) plunger of the syringe would need to be made of solid CO2 and 60 to 70 meters long otherwise the pressure would just push it out. Thus under a couple of meters of CO2 ice is not like;ly

    Posted

  • AUricle by AUricle

    wassock,

    Thanks, I understand.......but, I thought the sublimating CO2 is building the pressure, not the weight of the ice sheet overhead. Just like putting dry ice in a test tube and sealing the top with a rubber stopper. As the tube warms, the 'ice' sublimates to gas until enough pressure is built....not by the stopper...but by the pressure of the building gas. In our case, the ice sheet is weighing down so a combination of forces seems likely, no?

    Which brings up another question. Doesn't the ice sheet begin to form on the surface? The current model for channel formation seems to place the ice as 'floating' magically above the surface while the gas occupies the space in between.

    Anyway, in my 'model', the ice sheet is just a pressure vessel 'lid', containing the gas /liquid until it's great enough to break through..

    Is the 5 ATM relative to the local conditions? obviously 5 Earth ATM's is far greater than 5 Martain ATM's.....or is that an 'absolute' unequivocal number inherent to the chemical composition of the molecule?

    Posted

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

    My understanding is that the icelayer does form on/at the surface and it becomes thicker as winter progresses. In springtime, due to the solid-state greenhouse effect, it is the ice on/at the surface which sublimes first, which is where the gas comes from. It's not gas building up in an existing space between surface and icelayer, just the ice on/at the surface subliming into gas which becomes the 'gas filled space'.

    Posted

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

    But the lid has to be heavy enough to keep the pressure in, just like the saucepan lid when you boil your spuds generally isnt. That or it needs to be fixed down round the outside and engineered enough to take the strain. Atm is a unit of pressure, the pressure needed for liquid CO2 is the same everywhere regardless of the units you use. Same as water freezes,at 1 earth atmosphere,at 0C and 273K

    Kitharode the idea is, methinks,that the ice surface layer warms and gets toa temperature where solid can turn to gas. But gas takes up more volume than solid so for this to happen there needs to be space. So either theres a gap, or the sublimating gas lifts the ice, or where theres frozen dust there is pace in amongst the partcles. Thus its easier to get a volumne of gas o er arough or dusty surface then itwould be for a completely smooth surface. Ses me.

    Posted

  • Portyankina by Portyankina scientist in response to Kitharode's comment.

    I also have similar image to yours with some additions that wassock mentioned. Generally, the ice turns into gas in the same volume, but it has some additional volume inside voids of regolith, for example. And it can in some cases lift up the ice, but this seems very-very short-lived phenomena. I also think, the surface is so non-uniform that kilometers of levitating dry ice is a bit of a stretch. There will be places with CO2 frozen into the surface, i.e. with a good grip and areas with thiner ice, where it sublimates away fast and makes a hole in the sheet and so on.

    wassock: There is a possibility also that the ice makes bridges over the channels - we see in the lab that ice has ability to bridge small holes, but we only can grow mm-thick layers in our set-up, so we are far away from understanding how half-meter layer would behave. I am not sure if this is an advantage for green-house effect, because when there is no contact to the ground, there is no heat exchange and much less sublimation. But it would create a void and additional preference to channels' development.

    Posted

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

    Let me just set out what my understanding of the playing "field" is, just want to check if I've got this bit vaguely right:
    The actual surface of the planet here is pretty much in a state of permafrost, in the summer there's scope for a bit of wind blown dust but probably not much and any significant depths of dust (or grust) will be "fixed" as part of the permafrost. The spiders are eroded into this layer of permafrost (not as I had originally been imagining into the bare bedrock?).
    If that holds then come the autumn there will be a difference between the permafrost surface and any accumulations of windblown dust that there may be, and it would seem likely that dust would blow into the spiders and collect there. The difference I see between the 2 is that the permafrost is going to be a solid lump of material with all the space in between taken up with Ice of one sort or another. The windblown dust will have a degree of porosity and the spaces between particles will be filled by the ambient atmosphere. As everything freezes this interstitial gas will take up less space and if it freezes after a surface seal of ice has formed may even result in an area of reduced pressure beneath the ice over winter. Either way where there is previously free surface dust beneath the ice layer there will be space within it come the fall for a bit of ice to sublimate and turn into gas. I suspect that the thermal properties of a solid ice/dust surface and one which is gas/dust/ice will be different and one will warm up quicker. At the simplest end of things, there's less matter in a given volume of dust/gas than dust/ice so it will take less energy to increase it's temperature. Having some initial space in the dust layer makes it easier to get a big enough volume of gas to break through and cause the initial vent, once that happens and some of the dust is gone there's a bigger void for the next one (ignoring the fact that we need somehow to seal the hole. The ease/likelihood of breaking through is in this theory linked to the area of interconnected gas containing space beneath the ice and put simply the bigger this area the more likely the gas will find a weakness in the ice.
    So the key point from all this in "How do spiders form?" would be that any where that windblown dust can collect (like a depression) is more likely to have sub ice gas and thus experience some erosion when the gas/dust moves and thus next year will be a bigger depression/more likely to have loose dust/will get a bit more bigger.
    Would be useful to know if any of that is just plain wrong (like windless dunes)

    Posted

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

    Right or wrong, you get a round of applause from me. Good stuff wassock.

    You say "in the summer there's scope for a bit of wind blown dust but probably not much....". There could, perhaps, be more than we think. I've gathered the following bits, for examples;

    The dust storms of Mars are the largest in the solar system, capable of blanketing the entire red planet and lasting for months. Dust storms are most common during perihelion (southern summer, no icelayer). Observation since the 1950s has shown that the chances of a planet-wide dust storm in a particular Martian year are approximately one in three.

    Sounds like a meaningful supply to me...

    Posted

  • wassock by wassock moderator

    Kitharode, my picture is that the ground itself is frozen all year round save for a fairly thin layer which thaws, in the polar latitudes, but I dont really know enough about temperatures and surface make up to know if that is right
    Of course stuff may blow in from out of town, but I get the impression that theres not a lot of native loose dust

    Posted

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

    When you say "the ground itself is frozen all year round save for a fairly thin layer which thaws, in the polar latitudes" I can easily go along with that and I get the picture. I'm guessing that you're saying it is this 'thin thawed layer' only that can provide the native loose dust, which may be a relatively small amount. Have I got that right?

    The dust storms could be viewed as an occasional addition of 'thin layer' material, significantly or not, without affecting your basic idea. But how much dust is not a lot? What grust mixture is required to form spider channels? Do the astronomical timescales involved mean that only minimal amounts of grust are needed?

    Guess I'm thinking out loud here, rather than being helpful....

    Posted

  • wassock by wassock moderator

    Your first para reflects my understanding 2nd is the stuff I dunno, yet

    Posted

  • Portyankina by Portyankina scientist in response to wassock's comment.

    Yes, mostly correct description. Just couple of tiny corrections. Same as permafrost on Earth, the very top layer of martian surface is ice-free. This layer serves as an isolation for the rest of the ice, mostly because it has high porosity. So, there is a layer which is not dust, but still not filled with ice at least during summer (it is what I called regolith before in some posts). When fall comes, CO2 starts to condense first inside the voids (of either dust layer or regolith layer) - how deep it goes, I am not sure, I don't think I have seen any research on this topic myself, but I should check this. And only later the impermeable ice layer forms on top of that "dirty" CO2 layer.
    Another thing: CO2 gas has lower heat capacity than solid, but it is really hard to deposit the energy into the gas directly. As with atmosphere, surface heats firs, and it in turn heats up the gas. I think the most pressure increase happens because of additional sublimation, nit because of increasing temperature of the already available gas.
    And about the dust being additional helper for sublimation I fully agree.

    Posted

  • Portyankina by Portyankina scientist in response to Kitharode's comment.

    Some estimates say, polar geysers could provide up to third of the global dust storm volume. Yet when you settle it down to the ground, it's not impressive - only several mm thick layer, if I recall correctly. But over the whole planet.

    Anya

    Posted

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

    OK seems like I'm reading from the same sheet. My idea about the warming is that if you have two equal volumes of dust and CO2, one with solid CO2 and the other gas. They both contain the same amount of dust, which does the job of collecting the sun, and so both receive the same energy input. If this it the case then the gas dust mixture temp must increase more as there is less mass in the volume?

    Posted

  • AUricle by AUricle in response to Portyankina's comment.

    Anya,

    When you say "isolation", do you mean it is an "insulation" in that it protects the rest of the ice?

    As to the volume of available dust, isn't it known that the channels are 1-2 m in depth? If annually, the surfce is being 'chewed-up' and turned to 'grust', then is it wrong to assume that the dust layer itself must be between 1-2 meters in thickness?

    Posted

  • wassock by wassock moderator

    The surface dust may be thick but after the winter its frozen solid and only the top teeny bit thaws in the summer, but as I understand it how teeny is not known

    Posted

  • Portyankina by Portyankina scientist

    wassock: I guess, ideally if the dust is suspended uniformly in the gas and mixed up in the ice - yes. The dust might however settle down in gas - depends on how turbulent it stays. In addition, do not forget that the CO2 ice here is in thermal equilibrium with its gas, meaning, it will not warm up, it will sublime when energy is available.

    AUricle: Yes, I meant that the layer thermally protects the underlying ice.
    I think, you are misunderstanding smth: spiders are not created every year from scratch. Their channels are permanently there. The amount of surface that is eroded annually is not known well, but as we see no changes on HiRISE scale (0.5m/pix), it's relatively small.

    Posted

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

    I'm not suggesting that theres any sort of suspension or fluid bed going on here, just think of dry sand on the beach, a bucket full of sand will also contain a bit of air betwixt the grains. If you made it cold enough the air in the spaces would freeze, do it slowly and all the spaces will filled with frozen air do it quick and seal up some of the airways then the reduced volume of the ice will leave voids containing gas at less than the ambient atmospheric pressure.

    We're looking at the layer immediatley below the ice. So we have a substrate, sealed beneath the ice, made up of little bits which dont fit together too well, with the gaps in between are either filled with CO2 ice or bits of ice and voids/low pressure gas/tending toward vacuum depending on how it all freezes. The sun shines through the ice and hits the surface beneath which warms the darker particulate slightly causing the ice in contact with each warmed up little bit to warm and sumblime eventually. So at the ice/surface interface we have CO2 gas coming from the underside of the ice and the top layer of the surface. If there is any free space in the surface dust any gas will be able to move around and may act as a better vector for heat transfer than the ice which must have some insulating properties if the greenhouse jobbie is to work

    Posted

  • Portyankina by Portyankina scientist

    Sounds very reasonable to me.

    Posted

  • wassock by wassock moderator

    Hi Anya I think this area is familiar to you http://hirise-pds.lpl.arizona.edu/PDS/EXTRAS/RDR/ESP/ORB_013000_013099/ESP_013095_0935/ESP_013095_0935_RED.abrowse.jpg

    Do you have a ready explanation for why the fans follow curves?

    If I'm reading your paper on this area right the area to the right end with few fans is a slight incline left to right and the two areas with lots of fans slope down left to right so the curves don't seem to be affected by slope

    More on this on Citizen Scientists , bendy winds thread

    Posted

  • Portyankina by Portyankina scientist

    Hi!

    I do not have a ready answer, but I think, winds here drape over the complex topography. One would need to run some weather model over this area to understand if the winds follow the curves of the fans.

    Anya

    Posted

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

    Anya welcome back, we've missed you.

    The fans don't seem to have the same pattern every year, which indicates that the topography isn't the only factor.

    Posted

  • Portyankina by Portyankina scientist in response to wassock's comment.

    Thanks!

    Surely topo is not the only important thing! Seasonal winds may deviate from the average yearly pattern and jets may come at slightly different times (both time of the day and season).

    Posted

  • wassock by wassock moderator

    Absolutely but I've been looking at one of your papers which models a ballistic vent on a slope to produce a standard shape fan. If that is producing some of the fans which follow the terrain then when the wind blows across them they should be deformed, which I don't think we are seeing

    Posted

  • richardpalmerromero by richardpalmerromero in response to Portyankina's comment.

    Hiya I love Planet Four and am doing my bit. Has Beagle been found yet?

    Posted

  • Portyankina by Portyankina scientist in response to richardpalmerromero's comment.

    Hi!
    No, not yet. This is the last image from the hunt for it: http://www.uahirise.org/ESP_031198_1920 I personally doubt we will be able to see it: too high probability that its 1 m diameter body was destroyed at atmospheric entry.

    Anya

    Posted

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

    Odd looking craters in that image Anyway - lots of striations running to the top left and the craters appear to be 'open' on the top left edge. Moreso at the top of the pic than the bottom

    Posted

  • Kitharode by Kitharode moderator

    The craters are easily seen as craters if the light is coming in from the left. Is this the case?

    (Light from the right gives the impression of circular features surrounded by a 'moat').

    Posted

  • Portyankina by Portyankina scientist in response to Kitharode's comment.

    The most natural light direction on images for us, humans, is from top left corner. I have read explanations for why our brain prefers top to bottom: the most natural situation for humans is when illuminated by the sunlight and sunlight always comes from the sky = top. But why left is better than right? I do not know. I've seen speculations about prevailing right-handiness, but they do not look convincing because all left-handers I know see the things same way as right-handers.

    Then, the further away illumination is from this sweet spot "top-left", the harder it is to see image correctly. And at some point it switches to the opposite topo. Also interesting, that one can train own brain! I looked at so many spider images with light bottom-right that by now I see them correct. It does not work for craters though.

    Anya

    Posted

  • Noharrr by Noharrr

    How do we classify an image where almost all of the surface is covered with an overburden of dust? The dust ranges from moderately red through deep rust to chocolate brown. The coverage is nearly total, with a few minor gaps.

    How would you mark up such an image?

    I seem to get a lot of them. I use couple of Collection categories (#Red Mars and #Dark landscapes), but would appreciate some advice on more accurately classifying them and marking them up.

    Thanks for the privilege of working on real planetary data.

    Posted

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

    Hi,

    If you're talking about an image like APF0001xsz - I would say all of that is the surface layer and there is nothing to mark. The fans and blotches should come out looking black or sometimes (black or brown sometimes with a bit of blue if there is frost or the fan particles are sinking into the ice). If you have some specific examples post them, and we can take a look.

    Cheers,

    ~Meg

    Posted

  • Noharrr by Noharrr

    Thanks Meg! Your example is the kind of image I'm talking about. Another example is APF0000vqw

    [Meg wrote: If you're talking about an image like APF0001xsz - I would say all of that is the surface layer and there is nothing to mark.]

    Posted

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

    That image you mentioned is tricky one I might say nothing or mark two blotches on the spider in the middle on it's left side. We have many people review the same image and will combine the results to identify whether there is a fan or blotch, so don't worry too much just do your best. So if you missed something in an image or two chances are the other people who reviewed the image will have marked it. So it's really just going with your initial reaction when looking at the image. I hope that helps.

    Cheers,
    ~Meg

    Posted

  • wassock by wassock moderator

    Hi can someone take a look at this HiRise and say if it shows a big hill or a valley, cant make up my mind

    http://www.uahirise.org/PSP_002702_0935

    Need to look at the greyscale jpg, only half of which shows below

    enter image description here

    Posted

  • Kitharode by Kitharode moderator

    I'll dive in until a scientist gets here. 😉 Assuming sunlight comes from the right-ish, I'd have to go with hill. Actually, if you find the images adjacent to this one it'd be interesting to see if the hill is actually a dome !!

    Love the curvy lines. Looks like the erosion of some SPLD edges to me (?)

    Posted

  • PaulMetcalfe by PaulMetcalfe

    Suggestion for additional observational data.

    Firstly, if the scientific community are already doing the following or think the suggestion is not of any value then please ignore it. This is intended to be helpful from a research point of view and not to support any theory of mine. Theories come and go but to my mind evidence sought to prove or disprove them is essential.

    The suggestions below are very loosely based on my ideas in the ‘Just a Spider Theory’ thread.

    Applying the same marking principle as for fans and blotches could there be a specific tool for marking ‘Boulders’. I believe some could be what I can accept as Boulders but I also believe many can be ‘Ice Bubbles’ or ‘Balloons’ inflated by gas (possibly from vents beneath the surface).

    The first part would be to see if ‘Boulders’ appeared at the same spot or within say, a metre over a few seasonal cycles and that a Boulder was not present during the thawed season. However, due to my suggested dynamic creation of such ‘Boulders’ they would be liable to movement such as

    1/ On sloping terrain a Bubble could roll when it attains a certain mass.

    2/ It could be ejected or fragmented or leak at the base due to excess pressure created by its increase in mass.

    3/ It could be created within a spider and ejected.

    Anyway, an observational result would probably have to be based on a percentage occurrence on fairly level (not necessarily flat) terrain.

    The follow on observations would unfortunately be over a longer period (tens to hundreds of seasonal cycles) and where the first observation was positive and on terrain that does not already show a proliferation of spiders. It would simply be to see if a new spider develops at that location.

    Posted

  • wassock by wassock moderator

    Kith, my first impression was valley then I went with hill after a closer look, but I can see it either way. However the devils in the detail: most of the fans have some sort of relation with the layers (if layers they be, looks to me like massive open cast mine) , the fans form at the edge of the layers and I am visulising this as a series of flat terraces with cliffs/steep inclines at each edge. So if a hill the fans form at the top of the cliff, if a hole they form at the base of the cliff. Either way up the fans all point to the middle!

    Posted

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

    Paul, can you elaborate on how the bubbles would work, particularly the bit about them inflating? What do you suggest they are made from?

    Posted

  • JellyMonster by JellyMonster

    Some boulders do look unnatural - perhaps they are gas bubbles of some kind as Paul suggests. Is this a new phenomenon?

    Posted

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

    If the link works, have a look at the MOLA map on this image. I see the area as running straight across a long hill (not quite a dome) http://viewer.mars.asu.edu/planetview/inst/hirise/PSP_002702_0935_RED#start

    I get your point about the fans being at the top or the bottom of the 'cliff-face' depending on whether it's a hill or valley. I've got them as eating away at the foot of the cliffs (I call them fringe fans/spiders) and this type of fanning can be seen elsewhere. Mostly found in images on the Inca City side of the pole, between (roughly) Longitude 270 - 360 deg.

    Your image, at lat -86 and long 175, is definately on the SPLD, so I think we got that bit right. 😉

    The "fans all point to the middle" observation is interesting. If we're looking at a hill, perhaps there is a depressed area around it, a moat if you will, which forces the fans to 'fall' before they can climb. Is it possible that a sizable hill on Mars can capture and hold heat, then radiate that heat from the top of the hill and 'suck in' the surrounding atmosphere? Probably not, but it's all I've got. 😉

    Posted

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

    Paul. I like the way you think outside the box, or in this case outside the boulder. 😉 However, like wassock I'm not sure how bubbles on Mars would work.

    As you know, marking fans and blotches to help map the weather on Mars is the main focus here and boulders aren't really part of the P4 project at the moment, but by marking them with a #boulders tag we are helping to build up a specific image collection that I'm sure will be useful to the scientists in the future.

    Good stuff - Keep it coming.

    Posted

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

    I'm not best suited to answer your other questions in detail. Anya and Michael have done the previous detailed studies of Inca City, but the boulder features are seen when the ice is conclusively gone, so it would be hard for me to think they were bubbles because once the ice is gone, there would be no gas to keep them blown up, and I'd expect to see the feature disappear.

    I wanted to give a quick comment about the classification interface. Boulders are only really present in Inca City, so it's one of the reasons we didn't make a marking tool. The interesting thing we'd like to see with the boulders hashtag is that there is a certain time that fans/blotches should be seen near boulders, if Anya and Michael's theory is correct. So we're asking people to identify boulders with the hashtag so later we can see if there are seasonal fans and blotches associated with them at other times than expected. That would be an interesting result. Though the talk hashtags are not comprehensive it's only if someone wants to mark, so it means that if we don't spot anything we can't say there isn't activity outside the expected time frame. But we figured it's worth doing since Talk gives us the flexibility for a search like this, that the main interface wasn't designed for.

    Cheers,

    ~Meg

    Posted

  • rosemarybillington by rosemarybillington in response to Portyankina's comment.

    From: rosemarybillington
    6May 2014
    Hi Planet Four team. In reference to the very dark black markings on the surface of Mars, I do realise that the present science of Mars must probably be correct that most are wind blown sediment deposits of DRY deposits. However looking at the HiRise images of many of the craters and regions in the Arabia region of Mars such as Danielson crater the jet inky black deposits look more like streams of liquid oil which could have brought to the surface by various processes. Oil is of course is of biological origin from the remains of biological life billions of years ago trapped under pressure undersea to become oil. If so, then a biological past of Mars is there in the HiRise photos for all to see. Just a thought, I could be wrong, am I wrong about this?

    Posted

  • wassock by wassock moderator

    Rosemary, I think that most of the time the dark streaks on the surface are thought to be due the movement of the surface material revealing darker material beneath, which usually fades with time. There are some places where similar features have been suggested to be caused by liquid, but there is some debate about this. Not sure what you are actually looking at, there are a lot of features in the danielson, sometimes the darkest black on the surface is down to a deep shadow.
    If you could post a link or screenshot of what you are interested in (on the HiRise board) then we can have a proper look.

    I dont think you are seeing puddles of crude oil on the surface, mainly because there are instruments on the satellites which would notice something like that.

    Posted

  • rosemarybillington by rosemarybillington

    From: rosemarybillington
    7May 2014.
    Hi wassock & Planet Four team.
    In regards to the very dark inky jet black featues on the surface of Danielson crater that look so much like liquid oil here is link to the DLR nes archive in which one of the relevent images appear.
    Thank you. Rosemary.Image from 7th June 2012 News Archive of the DLR German AerospaceCentre of Danielson crater in colour 3d taken on 19th March 2012 by the HRSC camera onboard ESA's  Mars Express

    Posted

  • JellyMonster by JellyMonster

    Hi Rosemary - the link doesn't appear to be working.

    Posted

  • michaelaye by michaelaye scientist

    Just a quick comment and question:

    • Boulder are visible as well when there is still CO2 ice. Interestingly, at many locations boulders are co-located with the earliest appearence of fans, which leads to an obvious hypothesis that the presence of them somehow facilitates vent creation for the CO2 gas jets. We are thinking that the thermal conductivity of a 'peaking through' boulder will at least make the ice weakest around the boulder, so that any gas pressure from underneath will try to break out there. Hence the earliest fans around the boulders.
    • While I'm no expert in the precise content of oils (but i know there's a wide ranging definition), any oill deposits on the Martian surface bigger than several meters would easily be discovered by the high-resolution CRISM spectrometer experiment on the MRO satellite. The organic molecules that would make up those oil deposits have clear spectral lines that would be identifiable from space, if the deposit area is big enough for the CRISM resolution. CRISM resolution is around 20-30 m, but if there'd be organic molecule emission photons within that, I'm pretty sure CRISM would have detected them, they just wouldn't know where within that 30 m window the photons came from. So, no, I don't believe there's any surface oil anywhere on Mars. Another reason is that in the low pressure Martian atmosphere a lot of the hydrocarbons would just evaporate immediately (with some few residuals most likely). I also had a quick look at the 3 only images HiRISE made in Danielson crater but couldn't see anything especially dark. I think our fans are darker. 😉

    Posted

  • rosemarybillington by rosemarybillington

    13 May 2014
    Hi Michaelaye & Planet Four Team.
    As regards surface oil on Mars this has to be my last attempt to get through on the subject and admit that I have shot my bolt if you can DEFINITELY prove this wrong, because I respect your team of professional scientists all vey much. What I am saying is that both the superb technology and superb professional science of the time has overlooked something that mere citizen science of the time perhaps may not have, because the latter tends to work on common sense explanations rarther than full science which is always prone to dogma. Hence, if the link to DLR in Germany does not work anymore then please try links to the (British,U.K.) 'Sky at Night' magazine September 2012 Coverdisc CD and its eots_04 file. Open the file in Windows then open the Mars Danielson crater photo in it with Paint, enlarge a couple of times , save in BMP format, which doubles the resolution, set as Desktop backgroud and select Fill or Stretch mode. Put on x2 or more reading glasses, stand back or forward a little untill all is clear and et voila the oil is practically dripping out of the computer screen. You are all accomplished scientists and I am a strugging amateur nobody, but I simply fail to understand why you cannot simply see the obvious in this case. Whatever your reply I intend to gradually switch from mostly BOINC based citizen science to Zooniverse based citizen science because my poor comupter has been doing too much of the work so far and it is time that I did most of the work at least for a while to give it a well earned rest. Enough said .Rosemary over and definitely out.

    Posted

  • JellyMonster by JellyMonster

    Rosemary - something like this?.. http://www.planete-mars.com/images-de-mars-express-sur-le-site-esa/

    Posted

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

    The top image looks more like dunes of black sand than a liquid/ooze to me

    Rosemary, can you post one of your images for us to look at? You will need to save it somewhere like Dropbox and link to it your dlr link may not work because of the way this site works, it can be picky about how you code a link. Can you try posting the url as plain text rather than as a link

    Posted

  • p.titchin by p.titchin in response to rosemarybillington's comment.

    Sorry Rosemary, to me it just looks like dark deposits being covered by lighter soils slipping from higher up the crater wall. Looks like some darker surface exposed by a slippage towards the top of the slope as well. The 'black' appears to have formed dunes in the crater floor. I'll wait with interest to see if you can do as Wassock asks, and post us the actual image you are describing. ~ Pete.

    Posted

  • rosemarybillington by rosemarybillington

    Hi all at Planet Four.
    14th May 2014.
    Dear Planet Four team.
    Oh dear, I think I should leave it to Dr. Chris Lintott Director of the Zooniverse Project to step in here, because otherwise this is going nowhere fast. Dr. Chris Lintott is not only the Director of the Zooniverse Project but also is a regular contributor writer to the 'Sky at Night' Magazine that I have earlier cited. I am sure he could go to the September 2012 issue re look at eots_04 on the cover CD and give his verdict that I will surely accept. If he says yeah then we all come from Mars originally, if he says neah then it is time for a deep rethink, especially for me.
    Enough said. Yours respectfully, Rosemary.

    Posted

  • p.titchin by p.titchin in response to rosemarybillington's comment.

    Rosemary, I'm sure we want to see this image. I f we are not to see it , then I must await to see if Dr Lintott comments. Don't give up on us, by nature I suspect many of us just like to explore ideas ourselves. It is what attracts us toP4, and these boards. No one's ideas are knocked, just explored and discussed openly. As Horace said, " Parturient montes, nascetur ridiculus mus" 😃 ~Pete

    Posted

  • JellyMonster by JellyMonster in response to rosemarybillington's comment.

    This is as far as I can get - http://www.skyatnightmagazine.com/issue/september-2012-0 How do you access the magazine contents or cover CD?

    One other thing - I'm not sure what you mean when you say 'saving as a bitmap will double the resolution'? If an image is say 1024 x 960, and it is saved as a .BMP, it will still be 1024 x 960 on reopening.

    Posted

  • wassock by wassock moderator

    Dear all, I've copied this discussion over into it's own thread so we can let it run there. This thread is intended as a place to leave questions for the science team, rather than a discussion thread. Please post anything further on the "Dark Material...." thread on the citizen science board.

    Thanx

    Posted

  • PaulMetcalfe by PaulMetcalfe in response to wassock's comment.

    Hi everyone,
    Sorry I have not responded sooner but I have been otherwise engaged and will try to catch up on any comments over the next few days (circumstances permitting). I hope to respond shortly.

    Paul

    Posted

  • PaulMetcalfe by PaulMetcalfe in response to PaulMetcalfe's comment.

    This topic was started about 2 months ago

    I have had a quick look at the welcome responses and rather than respond to each individually, hope this will cover all. It was right that I was reminded this project at present is for plotting wind patterns and I will happily refer to ‘my’ Bubbles as boulders and hope the scientists do not dismiss the bubble idea out of hand.

    Although I accept that boulder features on defrosted ground are probably just that – Boulders, I could offer another explanation that would tie in with my Gas Bubble idea. Unfortunately, I have not viewed any pictures of Boulders on defrosted ground, so this is purely a remote possibility.

    IF a low-pressure vent exists it may not be apparent during defrosted times but as substantial ice forms the gas could blow the ice into a spherical shape that expands with time. Any dust debris carried by the gas from the vent within this bubble could drop around the vent creating a ‘solid’ structure (I am assuming that this mound is still in a state of freeze to stop it blowing away by wind at defrost time, although erosion into a less conical shape could be possible). However, it would probably be conical in shape and may show a blowhole at its apex. Many cycles later, this ‘solid’ mass may be too great for the gas to bore through and thus it is eroded away at the most pressurised easiest escape - the base (creating a Spider) and eventually washing the mound away. The gas can still in future cycles create ice bubbles but also score out Spider channels that it has now created and with a greater volume of gas trapped, the pressure will be all the greater and could possibly create bigger Spiders over time.

    Anyway, just for the record, one reason I look at these as bubbles is that most of them look spherical to me, which I equate to inflation by a gas. To my mind if a boulder (unless they are all spherical) at thaw time is covered by ice at freeze time, I would initially expect the ice covering to take on the shape of the boulder it covers.

    I will burst the bubble now and stick to fans and blotches. Hey, it is easier when my visits to the site are erratic.

    Paul

    Posted

  • wassock by wassock moderator

    Paul, "bubble" is normally associated with a volume of gas held within a flexiblr/elastic membrane. For this to fly you need some way to inflate somthing which is inherently solid and inflexible. CO2 ice, at The T and P on Mars, is not like ice back home in that theres no fluid slush where liquid and solid co-exist. Its either solid or gas.

    You also need a reason for the bubble to persist between winters whilst all around the ice melts. A while back I kicked the idea around with the science team of some sort of deposition going on at the vent point caused by the rapid pressure changes going on, but my physics wasn't up to it.

    Nice to have you back

    Posted

  • PaulMetcalfe by PaulMetcalfe in response to wassock's comment.

    The thing is that we don't actually know how elastic the ice on mars can be. If it is definitely not possible to have an ice bubble then I can accept that.

    I have not said that the bubble persists during the thaw period but that it could leave a deposit (mentioned above) that could resemble a boulder. My Chemistry and Physics on this matter is not brilliant and if a scientist says it is not possible for this to happen then I will accept that but keep an open mind.

    I am not trying to prove this right or wrong, just forwarding it as a possibility on an alien world.

    Posted

  • Portyankina by Portyankina scientist in response to PaulMetcalfe's comment.

    Hi Paul!

    I like this logical constriction of yours

    IF a low-pressure vent exists it may not be apparent during defrosted times but as substantial ice forms the gas could blow the ice into a spherical shape that expands with time. Any dust debris carried by the gas from the vent within this bubble could drop around the vent creating a ‘solid’ structure (I am assuming that this mound is still in a state of freeze to stop it blowing away by wind at defrost time, although erosion into a less conical shape could be possible). However, it would probably be conical in shape and may show a blowhole at its apex. Many cycles later, this ‘solid’ mass may be too great for the gas to bore through and thus it is eroded away at the most pressurised easiest escape - the base (creating a Spider) and eventually washing the mound away. The gas can still in future cycles create ice bubbles but also score out Spider channels that it has now created and with a greater volume of gas trapped, the pressure will be all the greater and could possibly create bigger Spiders over time.

    apart from the point of ice bubbles 😃

    The conical shapes of deposits around the low pressure vents are on my mind for long time, I think, we can see some of them in the images. Similar to cinder cone volcanoes but in much smaller scale.

    But the "ice bubbles hypothesis" is killed simply by the observation that the boulders are present and actually much better visible during ice-free season. Seasonal ice layer buries them partially, so in spring time they do not stick out of the surface completely. In summer however one can observe nice shadows and the round/ish shapes of the boulders. They might just look round to us because of the camera resolution > size of details. Or they might really be round/ish because the material they are made of are soft and erodes away easily.

    Anyway, nice to hear you entertaining ideas!
    Anya

    Posted

  • wassock by wassock moderator

    Fresh impacts on the surface are marked by dark ejecta, disturbances on dusty slopes causes dark smears, both thouight to be caused by darker material beneath the lighter coloured surface being exposed. Our own fans are darker than the underlying surface - because they are made up of subsurface material maybe? Ditto the tracks left by dust devils, dark on a pale surface.

    In all cases the dark colouration eventually fades in the sunshine - presumably the light coloured surface beneath the the "newly elevated to the surface" material then gets darker once it's out of the suns glare (this would sem to have to happen otherwise the churning of the surface over the millennia would have turned all the dark stuff light. So it appears we have some photochemistry going on. Has any one figured out what this reversible reaction is and does the widespreadness of this effect infer a fairly homogeneous (in terms of mineralogy) dust layer all over?

    Posted

  • PaulMetcalfe by PaulMetcalfe in response to Portyankina's comment.

    Thank you Anya for this very informative response to my OUT OF THE BOX suggestion; I concur with the possibility of the boulders being comparatively soft material that could be moulded by wind in summer and perhaps by ice in spring etc. into apparently spherical shapes. I of course accept the camera resolution or angle may be inappropriate to show the shapes exactly.

    The more important part of the suggestion is the initial part, I strongly consider that gas movement (from vent or sub-ice movement) may build boulders and Spiders and PERHAPS Spiders come from Boulder/Gas interaction in spring. Anyway, I think that is more your department than mine.

    Just to put the ‘Bubble/Balloon’ to bed in the right light (I hope) and to entertain. I would rather look a fool now, suggesting something generally accepted as improbable than to be kicking myself in years to come if an astronaut on Mars texts his mum and says ‘You know what, the Physics up here is weird. We have bubbles of gas filled ice – one just went POP – Heck, I think it was an egg – it just gave birth to a whopping Spider’.

    Thanks again.

    Paul

    Posted

  • p.titchin by p.titchin in response to PaulMetcalfe's comment.

    I've been following with interest. I've been wondering about the boulder/bubble connection with spiders. Am I right in thinking that the ice bubble/snowball evolution theory is over short periods, i.e. freeze /thaw martian seasons, where as current thoughts are that spiders form over a very much longer time scale? Also, there seem to be many 'snowball' type boulders that have not so far showing venting activity., All very intriguing! I tend to the view that any 'lump' on the surface will have it's outline smoothed and rounded by an ice covering, and where sublimation pressure builds up, is likely to provide a weakness in the ice sheet to facilitate venting. I'm sure there are many things going on. I just hope as we get to see more sequential images, the picture starts to clear! ~ Pete.

    Posted

  • PaulMetcalfe by PaulMetcalfe in response to p.titchin's comment.

    Just to answer you quickly Pete. When I first explained this idea, I suggested that any such evolution would probably take many years (possibly tens or hundreds). It would not be a quick process. Anyway, I've tucked it up and it is peacefully sleeping now unless the alarm clock goes off.

    Paul

    Posted

  • mquartner by mquartner

    I was wondering about the blue/teal color of some of the fans. Is the material in the blueish fans different than the material in the black fans and blotches?

    Posted

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

    This description of the current hypothesis for the blue color by Michael on the science team, I think will answer your question.

    Cheers,

    ~Meg

    Posted

  • wassock by wassock moderator

    HI Meg

    Seeing as how its hard to image an actual vent because the cameras are looking down, is there a way to get the cameras to look forwards (backwards) so we're looking at the horizon as we approach the pole? Preferably when the sun is on the far side to the camera. That way if there are any active vents we may have a chance of seeing them - as has been the case else where in the solar system.

    Posted

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

    Hi Wassock,

    That's a great question. I don't know the answer. I've passed it along to PI Candy Hansen, who is also deputy director of the HiRISE camera so she's probably the best to respond.

    Cheers,

    ~Meg

    Posted

  • CJ-DPI by CJ-DPI scientist

    Hi,

    Yes there is a way - but we haven't been successful yet. We can point the camera up to 27 deg from nadir, so that we can acquire stereo. What we have tried to do is to acquire 2 images on adjacent orbits (orbits are 2 hours) and then look at the anaglyph of the stereo pair. Anything sticking up above the surface should be pretty obvious. The problem is that we think the venting only lasts about 2 hours, so we have to be lucky to actually catch one. Also, we can't do this very often because it disrupts the atmospheric data being collected by the Mars Climate Sounder, another instrument on the payload.

    Candy

    Posted

  • DZM by DZM admin in response to CJ-DPI's comment.

    Thank you for the thorough answer, @CJ-DPI --! Always nice to see different people from the science teams around on Talk. 😃 We appreciate it!

    Posted

  • jshoe by jshoe in response to Portyankina's comment.

    Hi Anya, This is a non-technical question, but important to me to help recruit new members:
    How do I save a copy of an image and get back to it for later reference? Is there somewhere to go for operational questions and help?
    Also, to Jellyhead and others: I might suggest taking a look at the ongoing project that is mapping changes in seasonal fans and blotches near the South Pole. Spiders are a regular feature there and there is much discussion of them. Of course, the scientists are very familiar with that project also. (I thought Jellyhead was also working on it)

    Posted

  • wassock by wassock moderator

    Jshoe if you are talking about the classification images, just click discuss when you've done marking. Then you can either add a comment, open a discusdion or save the imsge to your personal collection

    Posted

  • Zigmeister by Zigmeister

    I have just classified something very interesting (OK, why else would anyone post 😃 ). What was special about this one was the there were only two or three very small circular craters. Top left were some 'collapse' features and, most interesting of all, there was a 'butterfly' crater of what I think of as a 'splash' type. meaning that it appears that an impact has produced a slush which rolls out onto the surrounding still frozen landscape and leaves this 'butterfly' outline. This particular one seems to have been formed and then filled in by some mechanism I can't identify.
    Normally, as on the Moon, such things happen by more impactor 'dust' plumes collapsing and covering them over through, probably, thousands or millions of years. Here, the land looks so smooth with this feature just poking up to show it's presence and shape that I can't think how it ended up looking like this.
    If you can ID which image I mean, any ideas?

    Posted

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

    Hi Zigmeister. Nice to see you here.

    I'm guessing that the image you mention is from the P4 Craters project (?) If so, there's little chance that we can ID the image because a crater image does not travel with its associated discussion. This is because the Craters project is (at the moment) purely for testing the interface of the project, rather than the images themselves. On here (the P4 fan and blotch interface) images can be inserted by typing their APF number, eg APF000262p but I don't think this works for the crater images - not yet anyway.

    Perhaps there is something similar to your image in Wassock's 'Double Craters' discussion. Here's the link. Cheers.

    Posted

  • backpages by backpages

    Greetings! Two things, on this page: http://talk.planetfour.org/#/boards/BPF0000008/discussions/DPF00008pv, I touched a key when I shouldn't have. There ARE craters in this photo. Second, I would be interested to know if, in numerous pics, there appears to be what look like 'new' impacts.....a gray scale image with craters, broken up by the random 'black' (small) craters with 'black' ejecta...no visible marks on the crater rim..complete full round rim with no breaks or damage. Whenever someone has the time, thanks!
    paul

    Posted

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

    Hi,

    Sorry for the late reply. I wanted to let you know I'm not ignoring your question, I'm not sure how to answer it. I'm on the science team from the main Planet Four project so it's not an expert in cratering. Hopefully James who is part of the cratering team can answer your question. If you any questions about fans or blotches, I'd be happy to answer those.

    Cheers,

    ~Meg

    Posted

  • Freethesouls by Freethesouls

    Moon zoo gave me an idea. After hitting the next button it says to check
    for
    interesting features and ect. to remind people to double check their data.
    Why
    not have something pop on the screen for other zooniverse projects or Planet
    four saying
    "Please, double check your data and check for interesting features"
    at least for
    the space programs. If Moon zoo uses something similar why not use
    it for other
    zoooniverse projects to remind people to double check their data or
    for Planet four. It could not
    hurt. Also, I love dinosaurs and if a project
    comes about that looks at
    dinosaur's bones or ect. that will become popular as a
    science
    project.

    Thanks,

    Tom (FREE THE SOULS)

    Posted

  • Freethesouls by Freethesouls

    Another idea is do the zooniverse have a chat room? If not maybe make a chat room like they have at cosmoquest.

    Posted

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

    Hi,

    Thanks for the suggestion. The problem is that interesting feature is subjective and without having context it's not much help since someone on the science team can't be sure or figure out sometimes what makes that feature interesting to the person who marked it. That's one of the reasons Talk was designed so that people could bring up and mention in an interactive way interesting features so it can be a discussion with the science team and other members of the Planet Four community. I think the Zooniverse is experimenting with how to better incorporate Talk.

    Cheers,

    ~Meg

    Posted

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

    Hi,

    A feature like that is coming in the very near future. If you have other suggestions related to the Zooniverse or Planet Four interface, the best place to stick them is in our Feature Requests thread. That way your suggestions and ideas won't get lost amongst the other posts when in the future we have funding to build version 2.0 of Planet Four.

    Cheers,

    ~Meg

    Posted

  • Freethesouls by Freethesouls in response to mschwamb's comment.

    OK, thank you very much 😃

    Posted

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

    Hi Tom,

    No problem we welcome suggestions.

    Cheers,

    ~Meg

    Posted