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Thread: Cornice Avalanches on Mars

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    Cornice Avalanches on Mars

    NASA thinks the hydrated salts at RSL sites they detected from orbit are evidence of flowing salt water on Mars. I think a better theory is that frost is blown into cornices at the crests of hills and these then make avalanches when they warm up. A cornice can lose structural strength as the temperature rises even before it melts, making an avalanche. The trails on Mars all start near the crests of hills, which makes sense for cornices but not for random salt deposits. The trails sometimes cross, which happens for avalanches on Earth but not for liquid water runoff. At the rate that salt could absorb water from the thin dry air on Mars it would probably just soak into the ground and not flow downhill. The trails are fixed width, which fits with cornice avalanches but not flowing water. There is no method for the salt to get back to the top of the hill. There is evidence of long term erosion that could not be done from a fixed amount of salt absorbing water from the air. Deep paths in rocky cliffs take time. Cornice avalanches could have been happening for millions of years.

    Here is a video (just over 1 minute) my son did with pictures (one correction, where he said "snow" should probably be "frost"):
    https://www.youtube.com/watch?v=1yKiqME4QLY

    Here is a blog keeping track of things.
    http://corniceavalanchesonmars.blogspot.com/

    Update 2/16/16: I now think "snow" is correct, so don't change to "frost". I had been told there was no snow on Mars but it now seems there is.
    Last edited by vincecate; 2016-Feb-16 at 12:36 PM.

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    It seems the vast majority of the "Against the Mainstream" ideas/theories are easily shot down within 24 hours but mine has lasted this long. I even got a private message along the lines of "interesting idea". So far I think my theory qualifies as "above average" for this forum. But I might be biased. :-)

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    You may well be running into a selection bias that very few of our forum members with any knowledge of Martian geo-, no, areology, frequent this subforum. But we've got some of 'm, perhaps some may spy your thread and be interested enough to take a peek. 29 days left.
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    I tried to post a link from Geology & Planetary Surfaces to here but that was not good. If after 29 days I don't get any feedback here would posting in Geology & Planetary Surfaces be ok? Or maybe just moving this there now?
    Last edited by vincecate; 2016-Feb-13 at 12:56 PM.

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    RSL are an interesting problem as distinct from slope streaks. They are thinner and seasonal with some possible relation to insolation. If you get a chance to review the first discovery paper with the multiple gifs taken over time to show a sequence of evolution of the RSL, try looking on the other side of the gifs opposite that of the RSL. While atten tion is centered on RSL, looking elsewhere on the same gifs I noticed what appeared to be an exhumation of a bright RSL or slope streak, The places where RSL appear are normally freer of dust. But I don't know if there may be more dust deposit upon the other side due to GCM which might help account for burial and exhumation of the bright streak..

    A troubling attribute from the images is that the RSL always seem to be in the same place. They never seem to alter their path from season to season. If they formed newly each season, one might expect some variation of their path at least once somewhere among all the different RSL. Some falling rock or even small dust accrual would divert at one path once in a while, But I have not seen any report from MRO observations that this has happened.

    It would seem that avalanches would suffer even more severely under this observational constraint. It seems the RSL have been there for a long time but seem to grow darker and then fade each season without new RSL being formed.

    At least for RSL, I prefer a scenario where, a long time ago when snow packs might have present, that thin streams of water with dissolved salts trickled down slope leaving a concentration of those salts to dry where the RSL are. If there are deliquescent salts like seen at the Phoenix site and by Curiosity, then the seasonal darkening could be due to possible changes in water vapor at sites whose temperature might allow the salts to absorb the water and darken during warmer periods only to dry out and lose water during a drier winter. At least this tries to address the problem that they appear to always form at the same place without path variation over the seasons.

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    Quote Originally Posted by borman View Post
    A troubling attribute from the images is that the RSL always seem to be in the same place. They never seem to alter their path from season to season.
    [...]
    At least for RSL, I prefer a scenario where, a long time ago when snow packs might have present, that thin streams of water with dissolved salts trickled down slope leaving a concentration of those salts to dry where the RSL are. If there are deliquescent salts like seen at the Phoenix site and by Curiosity, then the seasonal darkening could be due to possible changes in water vapor at sites whose temperature might allow the salts to absorb the water and darken during warmer periods only to dry out and lose water during a drier winter.
    First, they do get longer going into the season. This would fit with frost cornices getting bigger as the season went on and so sliding further before being all used up. It would not fit with your "path with concentration of salt" idea.

    Second, the paths do change some. It is not always exactly the same. This also contradicts your theory. Given that they are carved in rock at the top they are going to be mostly the same. Similar thing happens on cliffs with snow going over them on Earth.

    Something like Iron Sulfate has different formulas for different amounts of water. You can actually buy it with different amounts of water. I have played with it a bit and it does change color when hydrated and take a long time to "dry out". Our first experiment was "rained out" after a few days. Will be doing more. If the passing avalanche added some H20 to the ground in its path this would all make sense.

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    The deliquescent salts were perchlorates, not iron sulfide.
    There is a wiki page on perchlorates with a section relating to Mars.

    https://en.wikipedia.org/wiki/Perchlorate

    A couple quotes here:
    “Based on the temperature and pressure conditions on present-day Mars at the Phoenix lander site, conditions would allow a perchlorate salt solution to be stable in liquid form for a few hours each day during the summer.[16]”

    “On September 28, 2015, NASA announced that analyses of spectral data from the Compact Reconnaissance Imaging Spectrometer for Mars instrument (CRISM) onboard the Mars Reconnaissance Orbiter from four different locations where recurring slope lineae (RSL) are present found evidence for hydrated salts. The hydrated salts most consistent with the spectral absorption features are magnesium perchlorate, magnesium chlorate and sodium perchlorate. The findings strongly support the hypothesis that RSL form as a result of contemporary water activity on Mars.[26][27][28][29][30]”

    A Nature journal abstract reference:
    Spectral evidence for hydrated salts in recurring slope lineae on Mars
    http://www.nature.com/ngeo/journal/v.../ngeo2546.html

    The MRO has the CRISM instrument which makes detections.

    With respect to the RSL growing longer over the season, The lineae are there in advance of the darker albedo that goes down slope. They are much brighter and more closely match the background albedo but can be discerned from MRO images. These lighter streaks turn dark as the season progresses.

    If you can link the before and after MRO images that show new RSL forming without prior ghosts being present, I will be happy to download the high resolution MRO images to verify that new RSL are forming within the year.

    The advantage of deliquescent salts is that the little bit of water vapor in the atmosphere may preclude the need for an aquifer or other local source for the
    water. The idea here is somewhat an analogue to litmus paper being very slightly dampened as the summer progresses as insolation improves from higher altitudes towards lower elevations.

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    Quote Originally Posted by borman View Post
    The deliquescent salts were perchlorates, not iron sulfide.
    I have read things saying there may be iron sulfate but I was just saying "like iron sulfate" in that the water chemically combines with the salt. It may be something else. The point is that it may take a long time to "dry out" when the water is chemically combined.


    Quote Originally Posted by borman View Post

    If you can link the before and after MRO images that show new RSL forming without prior ghosts being present, I will be happy to download the high resolution MRO images to verify that new RSL are forming within the year.
    I have just read things like, "The new RSL follow almost, but not exactly, the same path as RSL from
    the previous year, following the topographic gradient. An animated gif of a larger subscene is available at
    http://hirise.lpl.arizona.edu/sim/ "
    http://www.lpl.arizona.edu/~shane/pu...ience_2011.pdf

    Just now when I followed their link I am not even sure what GIF they are talking about.

    In this video they talk about "rolling boulders on Mars". I think this is at an RSL site. It fits with my avalanche theory. It would not fit with your theory that it was just changing color but nothing was moving. The theory in that video is that rolling rocks are making the trails and the rolling rocks are coming from Earthquakes (or Marsquakes). I think this is clearly wrong as it does not work with the dark area getting longer during the season or them being in almost the same place every year. But the evidence of moving boulders is interesting.

    http://video.foxnews.com/v/146874107...#sp=show-clips
    Last edited by vincecate; 2016-Feb-15 at 04:11 PM.

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    Here is a gif that shows what I see:
    http://www.nasa.gov/mission_pages/MR.../pia14472.html
    The recurring, as opposed to newly formed, slope lineae get darker from the top outcrops and evolve down slope. But one can make out lighter paths that are present in advance of the approaching darker albedo. The lineae follow these paths or ghost lineae.

    Because it is less dusty at these locations, there is a better chance that perchlorates will remain exposed on more ghosts to perform as a water magnet to capture enough water vapor for albedo change. Whether there is enough water vapor volume at these site to collect to start a brine flow is an open question perhaps that could be addressed by MAVEN.

    As exciting as it would be to discover local water flow for biological and human mission reasons, water coming out of these outcrops is too surprising for me. No THEMIS heat signature and pumping an endless aquifer upslope every year seem too problematical and reason for skepticism.

    Recall that the droplets that formed on the legs of the Phoenix lander did so without the assistance of a brine flow, an aquifer, or a small geyser, or an avalanche. Recall that water ice discovered buried at the Phoenix site did not melt or collect drops but readily sublimed. Perchlorates blown onto the legs during landing appeared to be all that was needed to capture water vapor into drops.

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    Quote Originally Posted by borman View Post
    Here is a gif that shows what I see:
    http://www.nasa.gov/mission_pages/MR.../pia14472.html
    The recurring, as opposed to newly formed, slope lineae get darker from the top outcrops and evolve down slope. But one can make out lighter paths that are present in advance of the approaching darker albedo. The lineae follow these paths or ghost lineae.
    The dark paths appear all at once. One new dark path can suddently appear next to one that has been there awhile or one can suddenly extend. All dark paths are connected to the cliff. In your theory all the paths with salt would all gradually get darker at the same time. In your theory they might not be connected to the cliff by dark parts. In mine they all should connect to the cliff and each suddenly get dark after an avalanche passes. In your theory, after enough dust storms any salt should be covered over and any ancient paths lost to time. Mine it is a current thing that dust storms would not cover over. Looking better for my theory than yours.

    If this has been going on for millions of years, then there are "ghost paths" from long ago and most new paths will go over some "ghost path". But it may not be a path that was used last year.

    Quote Originally Posted by borman View Post
    As exciting as it would be to discover local water flow for biological and human mission reasons, water coming out of these outcrops is too surprising for me. No THEMIS heat signature and pumping an endless aquifer upslope every year seem too problematical and reason for skepticism.
    At least we both are sceptical of NASA's dominant theory. But I do think the wind blows frost into cornices that could be collected by humans.

    Quote Originally Posted by borman View Post
    Recall that the droplets that formed on the legs of the Phoenix lander did so without the assistance of a brine flow, an aquifer, or a small geyser, or an avalanche. Recall that water ice discovered buried at the Phoenix site did not melt or collect drops but readily sublimed. Perchlorates blown onto the legs during landing appeared to be all that was needed to capture water vapor into drops.
    Clearly it is possible for drops to form on the lander's legs, as they have great pictures of that. But to go from a few drops all the way to 5 meter wide flows of salt water is really a big leap. I don't buy it.

    Could you at least agree that my theory is more plausible than NASA's dominant theory of flowing salt water?
    Last edited by vincecate; 2016-Feb-15 at 07:54 PM.

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    Someone has told me that there is nothing like snow on Mars, only frost. If there are ice clouds near mountain tops how can anyone be sure that frozen water does not sometimes hit the mountain and stop flying?

    Update: It seems they can hit the ground:
    "The Phoenix LIDAR observations have demonstrated
    that water-ice crystals grow large enough
    to precipitate through the atmosphere of Mars.
    In the early morning hours, the clouds formed at
    ground level and at heights around 4 km because
    these were the coldest parts of the PBL."
    http://sci-hub.io/doi/10.1126/science.1172344

    If they are going to hit the ground, just past a hilltop where the air is not moving could collect frozen H2O into a cornice!
    Last edited by vincecate; 2016-Feb-15 at 10:43 PM.

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    Hi vincecate.
    To support your idea you need to supply some evidence that frost crystals can actually form cornices. Are there any terrestrial examples?
    Then you need to establish the direction of the prevailing wind in the observations. It is no use speculating about the wind creating frost cornices if it blows parallel to or against the crest.
    Then you have to explain how the H2O frost melts at temperatures and pressures that seem to be associated with brine rather than water. Brine has lower freezing points than water.

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    Quote Originally Posted by vincecate View Post
    First, they do get longer going into the season. This would fit with frost cornices getting bigger as the season went on and so sliding further before being all used up.
    RSL "appear and lengthen in the southern spring and summer". My expectation is that the cornices would form during winter and avalanche during spring getting smaller. Not that this would stop the RSL getting longer. Hypothetical cornices avalanching once does not explain the RSL and it is hard for a non-existing cornice to avalanche again ! But any frost could melt. On the other hand a reason that the RSL are thought to be brine seems to be that they form at the temperatures expected for brine, not water.
    Also see Spectral evidence for hydrated salts in recurring slope lineae on Mars (described in NASA confirms present-day salt water flows on Mars)

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    Quote Originally Posted by Reality Check View Post
    Hi vincecate.
    To support your idea you need to supply some evidence that frost crystals can actually form cornices. Are there any terrestrial examples?
    Then you need to establish the direction of the prevailing wind in the observations. It is no use speculating about the wind creating frost cornices if it blows parallel to or against the crest.
    Then you have to explain how the H2O frost melts at temperatures and pressures that seem to be associated with brine rather than water. Brine has lower freezing points than water.
    My comment just above yours has a link that shows precipitation from ice clouds on Mars. So at times there is ice in the air that is coming down. So now "snow" seems more like the source than "frost".

    The temperatures are around the freezing point of water. The problem is that at the low air pressure on Mars fresh water is either ice or a vapor but never a liquid. My kids and I have put some water in our vacuum chamber and watched it bubble till it turned to ice. Very cool. We also put in salt water and that did not bubble or freeze. My way around this "no melting fresh water" problem is that the structural strength of ice is greatly reduced as it gets close to the melting point. An avalanche can happen even though no ice has turned to water. This is very much like iron losing its strength as it gets closer to the melting point: https://www.youtube.com/watch?v=FzF1KySHmUA

    Yes, figuring out if the winds were right would be a good thing in evaluating this theory. I have added that to my todo list.
    There are a few experiments that might help evaluate this theory on my todo list:
    http://corniceavalanchesonmars.blogs...ion-items.html
    Last edited by vincecate; 2016-Feb-16 at 01:07 AM.

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    Quote Originally Posted by Reality Check View Post
    RSL "appear and lengthen in the southern spring and summer". My expectation is that the cornices would form during winter and avalanche during spring getting smaller. Not that this would stop the RSL getting longer. Hypothetical cornices avalanching once does not explain the RSL and it is hard for a non-existing cornice to avalanche again ! But any frost could melt.
    Also see Spectral evidence for hydrated salts in recurring slope lineae on Mars (described in NASA confirms present-day salt water flows on Mars)
    Ice in the Sun at these temperatures would not last long. It would sublimate. I don't think it can go for weeks even, let alone from winter through spring. I think the cornices are formed during the night and usually gone by mid-day due to the sun warming them up. My theory is that conditions at active RSL sites are right for snow at night and avalanches during the day. This would be a good test for my theory. I have added that to my list.
    Last edited by vincecate; 2016-Feb-16 at 01:29 AM.

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    Quote Originally Posted by vincecate View Post
    My comment just above yours has a link that shows precipitation from ice clouds on Mars. So at times there is ice in the air that is coming down. So now "snow" seems more like the source than "frost".
    Snow is not water-ice crystals.

    Quote Originally Posted by vincecate View Post
    The problem is that at the low air pressure on Mars fresh water is either ice or a vapor but never a liquid.
    Well you have just invalidated your theory. The RSL do not look like avalanches. They get continuously longer over period of months just like flows of liquids. And now you state that they cannot be flows of water. That leaves brines which for a specific pressure has a lower freezing point than water, i.e. could be liquid at the temperatures seen during the RSL.

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    Mars Water-Ice Clouds and Precipitation, Whiteway et. al; Science 03 Jul 2009: Vol. 325, Issue 5936, pp. 68-70DOI: 10.1126/science.1172344 (PDF) does not say that water-ice reaches the ground as frost. The abstract implies that the crystals melt near or on the ground and rise as water vapor to fall as crystals again.
    The light detection and ranging instrument on the Phoenix mission observed water-ice clouds in the atmosphere of Mars that were similar to cirrus clouds on Earth. Fall streaks in the cloud structure traced the precipitation of ice crystals toward the ground. Measurements of atmospheric dust indicated that the planetary boundary layer (PBL) on Mars was well mixed, up to heights of around 4 kilometers, by the summer daytime turbulence and convection. The water-ice clouds were detected at the top of the PBL and near the ground each night in late summer after the air temperature started decreasing. The interpretation is that water vapor mixed upward by daytime turbulence and convection forms ice crystal clouds at night that precipitate back toward the surface.
    The body of the paper has Fig 1: observations that end at ~500 meters; Fig 2: Fall streaks down to ~ 3 kilometers.
    Note that a planetary boundary layer does extend to the surface though.

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    Have you read the Wikipedia article on RSL: Seasonal flows on warm Martian slopes, vincecate?
    Distinctive properties of recurring slope lineae (RSL) include slow incremental growth, formation on warm slopes in warm seasons, and annual fading and recurrence,[14] showing a strong correlation with solar heating.
    ...
    The leading hypothesis involves the flow of brines —very salty water.[3][15][19][16][20][21] Salt deposits over much of Mars indicate that brine was abundant in Mars's past.[12][18] Salinity lowers the freezing point of water to sustain a liquid flow. Less saline water would freeze at the observed temperatures.[12] Thermal infrared data from the Thermal Emission Imaging System (THEMIS) onboard the 2001 Mars Odyssey orbiter, have allowed the temperature conditions under which RSL form to be constrained. While a small number of RSL are visible at temperatures above the freezing point of water, most are not, and many appear at temperatures as low as −43 C (230 K). Some scientists think that under these cold conditions, a brine of iron sulphate (Fe2(SO4)3) or calcium chloride (CaCl
    2) is the most likely mode of RSL formation.[22] Another team of scientists, using the CRISM instrument onboard MRO, reported that the evidence for hydrated salts is most consistent with the spectral absorption features of magnesium perchlorate (Mg(ClO4)2), magnesium chloride (MgCl2(H2O)x) and sodium perchlorate (NaClO
    4).[3][21]
    That "slow incremental growth" is more of a flow than the spurts expected from avalanches.

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    Quote Originally Posted by Reality Check View Post
    Snow is not water-ice crystals.
    If I ask Google "snow definition" it says, "atmospheric water vapour frozen into ice crystals and falling in light white flakes or lying on the ground as a white layer."

    Quote Originally Posted by Reality Check View Post
    Well you have just invalidated your theory. The RSL do not look like avalanches. They get continuously longer over period of months just like flows of liquids.
    In my theory RSLs are the trails of avalanches. They look very much like what happens when snow is going over a cliff on Earth. They do suddenly get dark. It is not a continuous thing. They have carved paths in the rock so later ones often go on the same route, and they get longer during the season. My theory is that there is more snow going into cornices overnight so that the larger cornices slide further before being used up.

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    Quote Originally Posted by Reality Check View Post
    That "slow incremental growth" is more of a flow than the spurts expected from avalanches.
    If you look at the "slow incremental growth" in the animated GIFs it is very consistent with a series of small avalanches on each of the different paths. Paths really do suddenly appear or suddenly get longer:
    http://www.nasa.gov/mission_pages/MR.../pia14472.html

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    Quote Originally Posted by Reality Check View Post
    does not say that water-ice reaches the ground as frost.
    The definition of frost is: a deposit of small white ice crystals formed on the ground or other surfaces when the temperature falls below freezing.

    So if vapor forms crystal in the air it is snow and if it forms them on a solid surface it is frost. So you can't form in the air and reach the ground as frost, you reach the ground as snow. Before starting this thread I had been told there was no snow on Mars, so I was going with frost, but I now believe there is H20 snow on Mars. I now think snow is the source for the cornices.

    From that paper:
    "Observations of water vapor and temperature
    during the Viking missions indicated that the
    atmosphere would be saturated with respect to
    water ice at night (2, 3), and it was suggested
    that the precipitation of ice crystals could be
    an important factor for the exchange of water
    between the atmosphere and surface (4).
    Here we report on experimental evidence that clouds
    and precipitation play a role in the exchange of
    water between the atmosphere and ground on Mars"

    It is not water precipitation, they are talking about snow.
    http://science.sciencemag.org.sci-hu...5/5936/68.full
    Last edited by vincecate; 2016-Feb-16 at 02:29 AM.

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    When the ice clouds seem to get snow to the ground is late summer nights:
    "The water-ice clouds were detected at the top of the PBL and near the ground each night in late summer after the air temperature started decreasing."
    http://science.sciencemag.org.sci-hu...5/5936/68.full

    And from this, the RSLs are active late summer:

    http://www.nasa.gov/mission_pages/MR.../pia14472.html

    I think we have our snow just when the Snow Cornices on Mars theory needs it. Snow cornices at night, avalanches by day, late summer. :-)

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    I appreciate all the comments by the way. Thanks! Keep them coming if you have more...

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    Quote Originally Posted by vincecate View Post
    If you look at the "slow incremental growth" in the animated GIFs it is very consistent with a series of small avalanches on each of the different paths. Paths really do suddenly appear or suddenly get longer:
    http://www.nasa.gov/mission_pages/MR.../pia14472.html
    Looking at a picture is often called "I see bunnies in the clouds" logic . Of course the animation looks like a like a series of small increments - it is a series of images each separated by days.
    The "slow incremental growth" is the evaluation of astronomers.

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    Quote Originally Posted by vincecate View Post
    The definition of frost is: a deposit of small white ice crystals formed on the ground or other surfaces when the temperature falls below freezing
    This is have water-ice crystals forming in clouds kilometers about the ground , not on the ground. It is not frost. Frost is when water freezes on the ground.
    The paper still does not say that anything reaches the ground as water-ice crystals (the paper).
    The paper says nothing about snow. The term it uses is water-ice crystals.
    The paper talks about precipitation of ice crystals, not precipitation of snow.

    Some more research for you: Your idea requires that the ground above the RSL be covered in "H2O frost/snow" maybe to depths of meters. Astronomers are very interested in water in any form on the surface of Mars. Please list the observations of this "frost/snow".

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    Quote Originally Posted by vincecate View Post
    When the ice clouds seem to get snow to the ground is late summer nights:
    Actually when there is no mention of the ice clouds getting snow to the ground in late summer nights. No snow. Not to the ground.
    "The water-ice clouds were detected at the top of the PBL and near the ground each night in late summer after the air temperature started decreasing."
    http://science.sciencemag.org.sci-hu...5/5936/68.full
    And try reading the actual contents of the paper - "near" means to ~500 meters of the surface at best because that is how far down their data went.

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    Quote Originally Posted by Reality Check View Post
    Some more research for you: Your idea requires that the ground above the RSL be covered in "H2O frost/snow" maybe to depths of meters. Astronomers are very interested in water in any form on the surface of Mars. Please list the observations of this "frost/snow".
    There does seem to be white parts that could be cornices near the tops of the cliffs in a number of the pictures. It seems people are thinking these are somehow not real white spots but I think they are real.

    Also, I have read that the HiRise camera seems to only be over active RSL spots in the afternoon. HiRise must have a polar orbit. So in the summer the plane of this orbit must be in the afternoon position as the planet rotates under it. So this may be making it such that most cornices are gone by the time the camera gets there. I know this seems funny, but it seems true.
    Last edited by vincecate; 2016-Feb-16 at 10:27 AM.

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    Quote Originally Posted by Reality Check View Post
    Actually when there is no mention of the ice clouds getting snow to the ground in late summer nights. No snow. Not to the ground.
    "The water-ice clouds were detected at the top of the PBL and near the ground each night in late summer after the air temperature started decreasing."
    http://science.sciencemag.org.sci-hu...5/5936/68.full
    And try reading the actual contents of the paper - "near" means to ~500 meters of the surface at best because that is how far down their data went.
    "Here
    we report on experimental evidence that clouds
    and precipitation play a role in the exchange of
    water between the atmosphere and ground on
    Mars"

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    Quote Originally Posted by Reality Check View Post
    This is have water-ice crystals forming in clouds kilometers about the ground , not on the ground. It is not frost. Frost is when water freezes on the ground.
    The paper still does not say that anything reaches the ground as water-ice crystals (the paper).
    The paper says nothing about snow. The term it uses is water-ice crystals.
    The paper talks about precipitation of ice crystals, not precipitation of snow.
    Again, before I started this thread I had been told that there was no H20 snow on Mars, so I was thinking frost was the source for the Cornices. I now think "water ice crystals formed in the atmosphere" are the source. This is the definition of snow, even if the paper does not use the word snow. Check Google for "snow definition", as I noted above.

    Snow:

    atmospheric water vapour frozen into ice crystals and falling in light white flakes or lying on the ground as a white layer.


    https://www.google.com.ai/search?sit....0.xLOwEUcCc6c

    precipitation: water that falls to the ground as rain, snow, etc.

    http://www.merriam-webster.com/dictionary/precipitation
    Last edited by vincecate; 2016-Feb-16 at 11:39 AM.

  30. #30
    Join Date
    Jul 2011
    Posts
    116
    Quote Originally Posted by Reality Check View Post
    The "slow incremental growth" is the evaluation of astronomers.
    Keep what Feynman said in mind whenever doing science:
    https://www.youtube.com/watch?v=EYPapE-3FRw
    Last edited by vincecate; 2016-Feb-16 at 07:52 PM.

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