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About Martian Ice News

  1. Jun 28, 2008 #1
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  3. Jun 28, 2008 #2

    Janus

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    It lasts too long for dry ice under those conditions. Both water ice and dry ice will sublimate when exposed, dry ice will do so much more quickly than water ice.
     
  4. Jun 28, 2008 #3
    If you watch the video of "disappearing ice" other changes also occur such as about 1/3 down a small lump appears to fall over and outside the trench small changes are noticed.

    My question would by what made those other changes? other disappearing chunks of ice or action of the lander?

    As for the time it takes for dry ice/water to sublimate how could one be sure they sublimate at different timescales on the Martian surface.

    The conditions are vastly different to anything found here. So the assumption of timescales may be inaccurate. Also dry ice is less likely to contain impurities than water hence the puzzling lack of impure remains after the "water" evaporates.

    The comment "the Phoenix lander has scraped a few centimeters down to an irrefutable layer of water ice in the martian arctic" seems a little too strong in its conviction.
     
  5. Jun 28, 2008 #4

    Janus

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    They know the temp & pressure at the area of the lander. They know the physical properties of both dry ice and water ice (including those at the local temp and pressure). Thus they know how fast each would sublimate under those conditions, It is also obvious that the difference in sublimation times must be significant enough to remove doubt for then to make said claim.
     
  6. Jun 29, 2008 #5
    Still the "known facts" relate to conditions on earth. Knowing the conditions on mars doesn't automatically mean they know 'all conditions' that may be present and unless the replicate those conditions including unknowns and test it here the assumptions made are significant enough to warrant caution.
    I remember plenty of unqualified claims such as the chunk of meteorite found in antarctica containing a fossil of an alien life form, turned out to be something totally different.

    I didn't mention it but I should have, why haven't they taken the 'ice' on board I am sure they have the necessary equipment to run 1000's of tests under fully known conditions. rather than the subjective test they have performed.

    That to me is a glaring omission.

    Isn't the search for water one of primary objectives of the mission, one would think that either the announcement would wait or the testing would jump any already waiting.
     
  7. Jun 29, 2008 #6

    Janus

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    What other "conditions" other than temp and pressure would you suggest that were not taken into account? The physics on Mars is no different that that on Earth.
     
  8. Jun 29, 2008 #7
    I have no idea what conditions may be different. But to rely on a video recording when you have a lab at hand seems like folly. also they said that there was an oddity, why no sediment within the ice?

    When something doesn't fit the alarm bells should be ringing.

    lwymarie raised the possibility it could be another material. maybe,maybe not. but the limited information available to us certainly leaves the question wide open. and I have recently learnt that fools and fanatics are so certain of themselves, the certainty in that article worries me. there is ample room for doubt ;)
     
  9. Jun 29, 2008 #8
    That's not the point Janus was making; There cannot possibly be any other conditions present, other than temperature and pressure. The Phoenix its self is equipped with an array of weather measuring equipment. As you input the data that's available, impossibilities are trimmed away which leaves possibilities. If enough is trimmed away, hopefully, your left with only one conclusion.

    And what is making anyone think that an alarm bell is ringing? What's not fitting?
     
  10. Jun 29, 2008 #9
    And if those conditions were replicated here on earth I am sure they are right but we aren't talking about earth we are talking about another planet.

    Whoa do I detect an extreme level of certainty there?

    Can you be certain at what rate dry ice and frozen water sublimate on mars. its extremely cold and conditions are very different. perhaps the wind effects it perhaps the lower density air effects it, what constituents in the Martian atmosphere may be interacting with it. the shade from the bloody great spaceship next to it will effect it. The reflections from the lander will effect it and the landers internal heat will effect it.
    From the article if you did not read it. If its puzzling to them then something is missing from the puzzle.

    I am not saying they are wrong I am just saying I agree with lwymarie there may well be another explanation. With a fully fitted lab why didn't they test it in there. any other test is subjective. that cannot be avoided.
     
    Last edited: Jun 29, 2008
  11. Jun 29, 2008 #10

    chroot

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    The physics of dry ice evaporation is the same everywhere in the universe, including Earth and Mars.

    You can build a machine that produces a cavity with Mars-like conditions within it (low-pressure CO2 atmosphere, cold temperatures, winds) here on Earth relatively simply. I'm not a planetary geologists, so I can't cite any specific experiments, but I'm sure such basic measurements have been made made times. If any geologists can cite an experiment, that'd be great.

    If you can't say how significant these effects would be, you cannot really use them in an argument.

    They're going to "touch it" soon -- using other instruments to conclusively show it's water ice. If I'm not mistaken the lander has some kind of a mass spectrometer on it, which would be a truly definitive measurement.

    - Warren
     
  12. Jun 29, 2008 #11

    DaveC426913

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    Much as you'd like it to be so, it's just not that different. Physics does not behave differently on other planets.

    And by the way, I do believe it has occurred to them to make their tests in the appropriate temps and pressures.

    Consider: scientists are able to "predict" conditions on Mars so well that the landing craft they've sent there are lasting 10 times longer than designed. If they didn't know their stuff pretty well, the craft would have gone belly up much sooner.
     
  13. Jun 29, 2008 #12
    Another planet which follows the same laws of physics that we experience here on Earth.

    Yes.

    Considering that the two will sublimate at different temperatures and pressures, yes. If you expose a small chunk of solid CO2 to the temperatures and pressures which we are detecting in the area, it will sublimate MUCH quicker than a same-sized chunk of H2O.
    Yes it's extremely cold, but that does not mean CO2 and H20 suddenly follows new laws. Trust me, we've experimented with CO2 and H20 here on Earth (in labs) at temperatures WELL below those at the Phoenix site.

    The phoenix lander is equipped with a wind speed indicator. Accounted for.

    The Phoenix lander is equipped with a pressure sensor. Accounted for.

    That's what the Phoenix lander is! It's a weather station specifically built to measure what constituents in the Martian atmosphere are interacting with it.

    It definitely will, and has. The shade helps preserve any ice that is exposed due to minimizing heating effects from the Sun. Accounted for. From the Phoenix home page...

    http://phoenix.lpl.arizona.edu/blogsPost.php?bID=178

    Reflections bouncing off of a lander which is located in a far North latitude, and which are coming from a faint, slowly fading Sun which will eventually disappear completely? Have you even been following the mission at all, or only trying to dissect specific bit of information that appears in the media from time to time?

    The lander is not emitting enough heat to interact with the sol around it. The Phoenix lander is insulated to be able to survive in the extreme cold conditions.
     
  14. Jun 29, 2008 #13

    LowlyPion

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    I think a more interesting question about the subsurface ice is the process by which it appears there under the surface.

    Now we can see it sublimate in the low pressure atmosphere (6 millibars or so) when exposed. There is to a certain extent the presumption that it sublimates through the porous Martian soil even when Phoenix scrapers aren't scraping it up though.

    So how did it get there in the first place?

    At one time there was apparently free flowing water at lower latitudes at least and that implies a bit of a higher global temperature for that way back when.

    Now if the water that is the ice we see today originally settled there as a result of water flow. That would suggest some melting at least of polar region ice accumulations at some point. (I trust we can say a river didn't run through the spot of the lander.)

    Alternatively, the ice that is seen there may possibly be layered in over polar ice cycles that get subsequently covered by layers of insulating dust sweeping over the polar region. (My uninformed guess.)

    Whatever the mechanism for it being there though suggests that it has a further story to tell about Martian climate history.
     
  15. Jun 29, 2008 #14
    B. Elliot
    LOL read Janus's tagline then.

    All I have done is support the original post. by saying how can they be "certain"

    I am sure the physics of dry ice sublimation is universal. I am just not sure the effects of the environment is. My references to the lander its reflectivity, internal heat and shadow are just obvious ones which may or may not effect the sublimation of whatever the compound was.

    Have they created the perfect insulator? must have missed that bulletin. The exterior of the craft can heat up (regardless of interior insulation) and that can then re-radiate to its surroundings.

    I am not saying the assumptions are wrong or the science is faulty, I am just saying given the many variables and possible unknowns (hence I don't know them) and the very fact we screw up here on earth often enough, there is room enough for doubt.

    Of all the comments here no one commented on Paige's puzzle. which is in contrast to what they expect given all they know. Therefore they can't know everything.

    If the teacher said it was midnight and your watch said it was midday would you accept what the teacher said or look out the window. I am looking out the window.

    But sadly its a known fact most people would accept the teacher (person in authority scientist/politician/parent/priest/shaman/rabbi/etc) and adjust their watch to his/her time without so much as a glance out the window.
     
  16. Jun 30, 2008 #15
    And so am I. Always. I'll pretty much make a safe bet that more than 90% of the people on this forum occasionally 'look out the window' also.

    With that said, how are you suggesting that we get 'better evidence' other than the data which Phoenix is providing?
     
  17. Jun 30, 2008 #16
    Also, it's a bit funny for a non-specialist to be questioning the results from a group of people who are highly specialized in their respective fields.

    Your not just doubting one teacher. Your doubting multitudes of teachers.
     
  18. Jun 30, 2008 #17

    LowlyPion

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    Excellent picture of the lander at top with the solar panels deployed, with the heatshield to the right middle and the parachute at the bottom.

    http://phoenix.lpl.arizona.edu/images/gallery/lg_647.jpg

    Almost like being there - but with popcorn.

    The terrain is certainly of interest as well. Aside from the natural texturing of the terrain looks like you can see the disturbances to the surface caused by landing.
     
  19. Jun 30, 2008 #18
    As I said in the first place. Take the ice in to the on board lab. test it using whatever means they have provided, I assume they have suitable mechanisms available to them, such as the mass spectrometer mentioned above.

    I am not doubting anyone actually. I am just "agreeing" the method of determining what the frozen white stuff seems subjective rather than conclusive. Which was the point of the original post.

    And as far as doubting a multitude of teachers, yes I do and I am proud of it. Its the doubters in history who have swum against the tide that make the real progress.

    Otherwise we would all be worshipping the sun God and not straying too far from shore lest we fall from the edge of the world.

    That is not a slight against anyone here. Its just to say sometimes we should be wary of what accept as the truth. Life is so busy that it is often easier to accept what we are told rather than wonder if there may be a different explanation. Often the reason we accept without question the 'teachings' of another authoritative person is because we *want* to believe it.
    Look at all the UFO enthusiasts. I even had one friend who firmly believed crop circles were the method of communication employed by ET's. When I explained that a pair of old chaps actually started the craze and they even explained how they did it in such a way that it "defied explanation". This person simply moved to a new position of the ET's "adopted" it as their method of communication. I could only chuckle to myself and promise my wife never to raise the subject again.

    If we look at the world around us we see the problems this unquestioning results in, especially when it reaches the level of fanaticism, and no-one is immune from it regardless of who they are and what they believe.

    Oh and thanks Lowlypion I appreciate your efforts ;)
     
  20. Jun 30, 2008 #19
    Following the lines of your proud doubters of history, they're doubts which changed history were testable and provided proof that the current accepted information is false. They didn't just make up theories and nor did they 'change history' based off pure untestable speculation. They had to provide cold, hard, observable, testable data to back up their claims. Otherwise, they're no closer to truly understanding than their sun god worshiping ancestors.

    What data at hand makes you think it could be something other than H20?
     
  21. Jun 30, 2008 #20

    LowlyPion

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    It's one thing of course to question authority and quite another to ignore facts that we have before us. Now while it may be that you haven't personally experienced the triple point of H2O, needless to say that point is known, just as the rest of the state behavior of water is over the P-V-T space. (A 3D plot of properties in Pressure-Volume-Temperature space.) Given the meteorological readings from the instrumentation on board we should have a pretty good idea then of just what point in the PVT space the lander is operating. It's a pretty safe bet then that with observed sublimation of the disrupted particulates and the exposed scrapings that what we are seeing there is behaving as we know water behaves. Additionally it is apparently not behaving as CO2 would at the same point in PVT space. That's a pretty strong case to be made for it being water and not CO2.

    My sense of it in looking at the pictures - and in this regard looking at the color corrected pictures and not so much relying on the animated bw GIF that is the video you mention - is that the sublimation results in discernible voiding of some of the areas of the exposure and a lowering of the surface in the scraped areas. Also of interest are later photos of the trenches that show further sublimation. (See Sol 33 in particular.)

    Moreover, drawing from personal experience and looking at the terrain that Phoenix finds itself in, I don't see anything that disagrees then with those observations, so much as really reminding me of pretty dirty snow pack that one sometimes sees roadside where the roads have been heavily sanded for travel. Now I realize that is not scientific and only anecdotal, but for me it does reinforce my agreement that what is seen in the pictures is water - sublimating - as one expects water to behave in such conditions.

    As to using the TEGA spectrometry ovens those efforts are under way and I'm sure as soon as those results are available we will all know more.
     
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