Martian sky is BLUE, tell NASA!

[extrasense]

Jon,<br /><br />Unfortunately, (3) is what the theoreticians often do, for living, which it is well seen from your references - as a theoretician myself I know <img src="/images/icons/smile.gif" /> <br /><br />Anyway, the thing is not settled to me. Funny, how $20 camera and the rest of little instruments, would save $billions and tonns of little gray cells<br /><br />e <img src="/images/icons/wink.gif" /> s<br /><br />

 

[JonClarke]

The references I gave are of analysis of actual data from the surface of Mars, not theoretical models.<br /><br />A $20 camera would not work on Mars. It would not be able to survive the noise and vibration of launch, the cold, heat, and hard radiation of transit, and the cold, dust and hard radiation of the martian surface. Nor would it supply the wide range of spectral dat in bands well beyond the human limit that most of the cameras that have landed on Mars have achieved.<br /><br /><br />Jon<br /> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[extrasense]

--- A $20 camera would not work on Mars. ---<br /><br />Well, I am ready to throw in $100 more <img src="/images/icons/smile.gif" /><br />I mean, in <b>addition</b> to the six cameras that are already there.<br /><br /><b>The calibration target is no good</b>, this is the root of problem. You need, in addition to the pure colors, the white and the white added colors like R1=255.240.240 etc.<br /><br />The instrumentation on the rover is most wanting, no doubt about it.<br /><br />ES<br />

 

[JonClarke]

IYHO<br /><br />Those who actually use the data from the rover are quite impressed by its capabilities. Those wh are actually imvolved with image processing think the calibration target very impressive and useful.<br /><br />Of course we all want more. Roll on ExoMars and MSL. But people like you will still be claiming the sky is blue when they get to mars.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

Let's be systematic.<br /><br />1. What evidence is there that the mars sky is blue?<br /><br />2. What evidence is there that it is dust coloured?<br /><br />3. What what would falsify the conclusions of 1 or 2?<br /><br />I will say for that the body of peer reviewed publsihed research by multiple independent teams of international scientists using different imaging systems on different spacrcraft over a thirty year period on different locations on Mars is very strong evidence. To falsify it one would need a greater body of work either reworking the original data or from future missions.<br /><br />What to the blue sky advocates says?<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[extrasense]

--- people like you will still be claiming the sky is blue ---<br /><br />Jon, <br /><br />you misundestand my position. A single picture worth thousand words. I had no opinion on the Martian sky color whatsoever, until I have discovered that:<br />1. There is a simple formula that produces acceptable representation of the calibration colors, from filtered images.<br />2. That this simple formula produces cyan like color for the Martian sky<br /><br />This is all one needs to know. What are the consequences of those facts?<br /> <br />1. Lets say, there is different formula which still produces acceptable representation of the calibration colors from same filtered images. This means only that we do not have enough information, and can not infere the actual sky color from the data. One must conclude then, that <b>we dont know what the Martian sky color is</b>.<br /><br />2. As it stands now, there is only one candidate formula, and it produces cyan color. One has to assume then, that <b>the Martian sky color is cyan.</b><br /><br />e <img src="/images/icons/smile.gif" /> s<br /><br />PS.<br /><br />Compare the picture of calibration target, taken directly on Earth, with the same restored from filtered images from Mars. A remarkable reproduction of the colors it is! <br />http://mywebpages.comcast.net/mycommon/color-e.jpg <br />http://mywebpages.comcast.net/mycommon/colors.jpg <br /><br />And, here is the true sky color on Mars: <br />http://mars.gh.wh.uni-dortmund.de/mer/opportunity/413/tn/1P164843722EFF51Y2P2663L5M1_L4L5L5L5L6.jpg.html <br /><br />To read about the formula, go here:<br />http://mars.gh.wh.uni-dortmund.de/mer/<br />

 

[yevaud]

I would ask how it is that you think you know what you're talking about.<br /><br />And then I remember who I'm speaking with.<br /><br />When you get done nattering on about Remote Sensing - of which you know nothing - you go yell for me. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[arit]

Extrasense!!!!!<br /><br />There is a guy over the phenomena forum that wanted to talk to you. His name is bigbrain.<br /><br />Regards,<br /><br />arit <div class="Discussion_UserSignature"> <span style="font-size:6pt;color:#009999;font-family:Verdana"><span style="font-size:6pt;color:#009999"><font face="Times New Roman"><strong><strong><span style="font-size:10pt;color:#009999;font-family:'CourierNew'"><p> </p><p><strong><span style="font-size:10pt;color:#009999;font-family:'CourierNew'">"We will either find a way, or make one!" - Hannibal<br /> </span></strong></p><p><strong><span style="font-size:10pt;color:#009999;font-family:'CourierNew'"><br /></span></strong></p></span></strong></strong></font></span></span> </div>

 

[telfrow]

<img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>

 

[JonClarke]

I understand your position well enough.<br /><br />The question is, what would falsify it for you?<br /><br />The other question is, have you actually read the papers I referenced?<br /><br />You should be aware that it is possible to write an algorithm that can turn the sky any colour you want. The issue is not what is possible, but what is actually the case.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[yevaud]

Arit:<br /><br /><img src="/images/icons/smile.gif" /><br /><br />"Midget Tag-Team Pesudoscience Wrestling Match." <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[extrasense]

Jon, <br /><br />What for would I read the papers? I've read abstracts you've pointed to, and there is nothing to guarantee that the results are not incorrect there.<br />If I would point authors to a mistake in such a paper, they would admit it, but come up with a correction, containing new <b>mistakes</b>.<br /><br />Back to my Consequence 1. You are saying that you could come up with algorithm, that would produce any sky color you want.<br />So, for you the color is <b>your</b> choice.<br />Fine, but do not suggest then that others were to make the <b>same</b> choice. <br />It is not science then for you, that's all. You simply are circling the wagons.<br /><br />e <img src="/images/icons/smile.gif" /> s

 

[telfrow]

<img src="/images/icons/rolleyes.gif" /> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>

 

[yevaud]

<font color="yellow">Back to my Consequence 1. You are saying that you could come up with algorithm, that would produce any sky color you want. </font><br /><br />That's not even remotely how it works...not that you'd know that... <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[JonClarke]

Why would you read the papers? becauyse that is where the data is. Unless you read them (and understand) them you are in no position to comment on the issues. Go to a local university librarey, read and digest the contents of these articles, then come back. if you can't do this, I can post you the papers. if you don''t want to do this, then you don't have a leg to stand on.<br /><br />You can make algorithms to do anythign, it does not make it true. You can mathematically transform as map of the surface of the earth into the inside of a hollow sphere - but it does not make the earth a hollow sphere. That matters is the evidence, not the mathematics. That is why not all choices are equivalent. <br /><br />That is why the actual papers of martian sky colour deal with the actual observations, not the mathematical transformations which are only tools. For example the Viking paper discusses spectral radiance and reflectance of different images of rocks and the sky at different times. It compares the results with information from laboratory studies, ground tests, telescopic observation, and the use of calibration targets. They show that the radiance of the Martian sky is almost exactly the same as that of the surface, except brighter. this is what you would expect from an atmosphere that contains dust and a surface that is coated by the same dust. Their conclusion is that the Viking 1 sky colour at the tiome of imaging had a Munsell colour of (9YR)5/4 and a NBS-ISCC colour of 76-77 (light to moderate yelloowish brown. At the Viking 2 site the values were (9YR)4/4 and 77 (moderate yellowish brown.<br /><br />I chose the the dust coloured sky because the best evidence from multiple sources says this is the case. This is a reasoned and informed choice. You chose a blue sky because of what ????<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

Mars landers don't just determine the sky colour, they also measure the amount of dust in the atmosphere. The amount of dust determines the optical density of the atmosphere, the more dust the greater the density, expressed as a numerical value. The numerical value increases with increased scattering. A perfectly transparent medium has a value of 0.<br /><br />On earth, a very dense smog over a large city like Los Angeles will have an optical density of 1.0. A clear day will have an optical density of 0.1 http://starryskies.com/solar_system/mars/spirit/dust.html . The infamous SE Asian brown haze has optical densities of 0.4-0.8 http://www.sdnbd.org/sdi/issues/climate_change/asian-brown-report/Part%20I.pdf . The atmosphere over the Sahara is typically about 0.2, with the intense storm of 2000 having an optical depth of 2.0 http://www.ims.metu.edu.tr/cv/oguz/dust_jgr_atm.pdf . Values as high as 6.0 have been reported http://geophysics.tau.ac.il/meidex/Publications/Paper1/Paper1a.htm . Extreme terrestrial dust storms can have optical depths as high as 12, measured in the infamous “black” storm of China in 1993. http://www.kccar.re.kr/papers/13_fulltext.pdf <br /><br />The optical depth over the first 210 sols at the Viking 1 landing site as being between 0.4 and 2.5 (during a dust storm). Most of the time it was between 0.4 and 0.8. At the Viking 2 site optical density varied between 0.2 and 1.6 over the first 180 sols. Much of the time it was between 0.4 and 1.0. http://adsabs.harvard.edu/cgi-bin/nph-bib_que</safety_wrapper <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[petepan]

Wow!<br /><br />great info Jon<br /><br /><img src="/images/icons/smile.gif" /> <img src="/images/icons/smile.gif" />

 

[extrasense]

Jon,<br /><br />what you are saying, that the more dust, the brighter sky. This points to scattered light.<br /><br />The fine dust that might be out there, probably is just scatering the light then - which is the most likely to produce a BLUE or WHITE sky, no matter what the color of particles' material is.<br /><br />e <img src="/images/icons/smile.gif" /> s<br />

 

[JonClarke]

Optical scattering of light is very complicated. As I understand it it works like this.<br /><br />Molecular scattering causes blue light, this is known as Rayleigh scattering. We are all familiar with this.<br /><br />Larger particles cause Mie scattering. This is typically whitish, which is why the sky is white on a hazy day is. The suspended Martian dust is of the order of 1-2 microns, so Mie scattering is very strong.<br /><br />If the particles are strongly coloured, for example by iron oxides and oxyhydroxides, they will tint the light. This is why the light goes yellowish during a terrestrial dust storm. the same occurs on Mars. <br /><br />However the Martian particles are irregular scattering is not even. Blue light is forward-scattered. This forms a bluish white zone round the sun. This is most noticable at sunrise and sunset.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[extrasense]

Jon, <br /><br />You state that Mia scattering, like with clouds, is strong and makes for white. Then you have a bit of Raleigh scattering on the smallest particles and CO2 molecules, that makes for a blue tint. <br />Still blue sky is not unlikely at all.<br /><br />e <img src="/images/icons/smile.gif" /> s<br />

 

[robnissen]

Jon, I was going to suggest early in this thread not to waste your time (I don't generally quote the bible, but there is something in there about casting pearls before swine.) But I'm glad I didn't, the two posts of yours describing the Martian atmosphere were tremendous. Thx for the great posts.

 

[silylene old]

I sure wasn't expecting to find anything meaningful in this thread.<br /><br />Then I read Jon's posts. Thanks for a good clear explanation of the Martian sky colors.<br /><br /> <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[yevaud]

Rayleigh scattering isn't just dependent on the presence of atmosphere - it's also dependent on the constitution of said atmosphere.<br /><br />The Blue light is scattered preferentially by the presence of Oxygen and Nitrogen. Virtually none of the first, and only traces of the second. Ergo, little blue scatter.<br /><br />Mie, or Aerosol scattering, is different. It will scatter whatever wavelength's impinge upon a molecule, hit-or-miss. It's not as wavelength-dependent, as is Rayleigh scattering. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[JonClarke]

Vevuad<br /><br />I too have read that that it is primarily O2 and N2 that causes blue Rayleigh scattering whereas CO2 has very little, but I have not found a specific source. Do you have one? I am a long way from Well's "Geophysics of Mars" which I think had a discussion of this.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

It is all a matter of degree.<br /><br />On earth with a clear sky Raleigh scattering is strongest because there are relatively few particles to cause Mie scattering. However you don't need a lot of dust or haze to turn the sky greyish white.<br /><br />On Mars there is very little Rayleigh scattering because the atmosphere is so thin and because CO2 does not cause much of it anyway. Mie scattering is very strong in the Martian atmosphere because of the dust. The composition of the dust tinges the Mie-scattered light ochre. This overwhelms what little Rayleigh scattering is present.<br /><br />It is a little bit like walking into a room at night illuminated by a faint blue light from fluorescent street lighting outside. When you turn the incandescent light on the blue light is completely overwhelmed by the yellow-white glow from the bulb.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>