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Space Science

The Blue Skies Of Mars 15

Posted by Hemos from the interesting-stuff dept.
Alien54 writes: "An interesting article from a German site (but in English!) on the possible correct color corrections for the NASA Mars lander photos is given here and here. Wait for the photos to load. "
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The Blue Skies of Mars More

The Blue Skies of Mars

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  • So...is the point that these photos (and al the Mars missions) have been faked? If so, why?
  • Sure, on the colour 'corrected' versions, the martian sky and landscape look very much more earthlike. However, the white parts of the spacecraft have suddenly turned blue. Furthermore I think NASA's scientific approach to processing the camera data is more convincing than the artistic approach the maker of this site takes. He just adjusted the colour balance until his intuition told him the picture looked 'right', while ofcourse human intuition has been calibrated for earth, and not for mars.
    I don't really see what NASA could possibly have to gain by a 'colour mars red' conspiracy, so I'll just file this site under X.
  • Forgot to mention that the maker of this site also claims to have spotted 4 martians on the pathfinder pictures, which NASA has hidden from us. If this guy isn't joking, he must be Fox Mulder :)
  • I corrected this. See the filter-curves on the same page. if you want to talk about this, join IRC-channel #bluemars on EFnet
  • Depends on what you mean by faked...

    It looks like this stems ftom the original Viking missions. IIRC the first pictures seen as they were sent back to earth showed an almost blue sky much like earth's. This was a surprise to NASA so they checked the gain used on the different colour channels (the camera sent back seperate red, green and blue images) used and found that they had given a higher bias to the blue channel than they should have. Removing this extra gain caused the images to shift back into the red images we know.

    This article seems to suggest that NASA should not have removed the excess blue from the images..

    *shrug* images is images load these ones into the GIMP and you would probably be able to give Mars a green sky just by changing the colour balance...
  • So, I got my old login back. Please do not use the plastic-casing for calibration, use the calibrations charts which are place on the lander. If you want to discuss, join #bluemars on EFnet
  • He says, "With the same method [ ] one arrives to 1 also with the graphic data Mars of the Pathfinders (Pic. F) at this colour (Pic. G), whereby however the sharpness of the original pictures by far not here is comparable with the excellent Viking data, there with the Pathfinder mission a information-reducing picture compression (comparable with JPEG) one used."

    What method? Arbitrarially increasing the blue and the green because you liked how it looked on the Viking images?

    The guy is also woefully misinformed about the amount of water in the atmosphere and the persistance of dust in the atmosphere.

    Anomalous: inconsistent with or deviating from what is usual, normal, or expected
  • ... because brightness on images if relative. Your eyes/brain adept to the current absolute brightness so the absolute brightness of the image is irrelevant. On the original data (right of the large images) you see, that the sky ad midday is about half to one third the brightness as on Earth the same local time. If you were on the surface of Mars, you could not decide if you were on Mars or on Earth in 20-30km above surface, beside of the local position of course.

  • This is a pretty cool idea, but I question his methods of determining how much color correction should be applied.

    The pictures look great, though they kind of ruin the mental image I (and probably a bunch of people) have of Mars as the "Red Planet".

    darren


    Cthulhu for President! [cthulhu.org]
  • Do you have any more information on how these calibration charts are used?

    Simply looking at a calibration chart through normal camera optics is meaningless. The human brain will try and adjust the colour balance to the earth norm because that is what we are wired for.

    What is really needed is a measure of the martian light used to illuminate a white standard across the full UV-Vis-NearIR spectrum. Once that is known and the response of the optics used to take the pictures on mars is known to every frequency in that spectrum you can start to make some colour calibrations.

    Using CIE human colour response curves for red, green and blue would then give an impression of how a human on Mars would probably see the colours. To be honest, because this is a function of the iluminating light and because the brain does so much processing based on what it expects to see, it will probably 'look' much like the earth norm.

    True colour (for anything other than single wavelength laser) is impossible to define without a human observer, colour is purely a function of our biological make-up. We will see what we want to see.
  • Hello, AC, nice of you to join us. Why don't you get an ID and we can talk.

    The slightly blue white plastic case of the lander is normal, if you do not like it, take a look at the original image, which shows also blue sky.

    One can't tell if the blue-white plastic case is normal without a color standard to test it against. The apparent color of an object is a function of its reflective properties and the spectrum of light used to illuminate it. Something which is blue-white plastic on Eath may not appear blue-white on Mars if the spectrum of the incident light does not have the same spectral characteristics.

    We can't compare to the original image if the original image hasn't been color corrected, but needs to be. And it appears to me that the original image has not been (properly) color corrected.

    Furthermore, why would you expect that a method that "works" on Viking would work on Pathfinder unless the imaging hardware were identical?

    Anomalous: inconsistent with or deviating from what is usual, normal, or expected
  • The image correction was added, according to NASA, because the blue diode also responded to infra red, thus making the blue signal stronger than it really was.
    This is not unheard of, it probably means that the second harmonic of the wavelength detected by the blue detector, which falls in the (infra)red part of the spectrum (twice the wavelength) also causes a blue signal.
    A similar process makes plants green. Plants absorb red light for photosynthesis, but the second harmonic of this wavelength (twice the frequency, or half the wavelength) is absorbed too, making plants white minus lots of red and some blue = green.
  • The calibration charts are a very hot topic at AMES/JPL/NASA. So hot, they "forgot" them on the Pathfinder Mission! I cannot understand, why they didnt not put an ISO-colorchart on the Pathfinder-Lander. This is not excusable in any scientific way! I have images from the Viking-Lander taken on Earth which show the calibration charts in Earth light, but cannot get any scientific information about the charts. The aim is not to start detailed frequency analysis on the light on Mars, I just want to give an impression how an human would see it when standing on the surface himself. The quality I want to achieve is comparable with that you expect from a photo-lab for you holiday pictures. And for that quality, the calibration charts and all data we have is sufficient.
  • People are currently doing harsh-weather equipment tests in the Arctic deserts, since they approximate some of the conditions on Mars (i.e. - very low temp., strong winds blowing rock grit, etc.).
    But I'm not sure where you're going with this. I don't think that it's scientifically valid to match the colors of the rocks and then have everything else follow from that...
  • Please, first look/think than write ;-) On the two first large color images on my page, you can easily see two color calibration charts on each of them. The small white/black/red/green/blue charts. These charts itself are sufficient to produce a color-quality you expect from a photo-lab for holiday pictures. If you want to have more precise colors, you need scientific data about these charts, or a calibrated copy of them. Both seems to be not available from AMES/JPL/NASA, you can guess for which reason... For the same reason, they deliberatly "forgot" the color-charts on the Pathfinder mission, thought there are ISO-norms for scanner-CCD-cams used there. Instead of this, they placed undefined pastell colored spots on the Lander!

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