Thursday, January 17, 2008
Revisting the True Colors of Mars
Back in October 2007 we posted a blog entry on the color correction problem NASA has historically had with images taken from the Martian surface. We deal with this specifically in chapter 11 of Dark Mission, and also posted articles on it on the Enterprise Mission web site several years ago.
As we showed in those articles, NASA has deliberately altered the colors of the images to make the Martian sky appear an absurd “Technicolor red,” when in fact all the evidence clearly shows that the true color of the Martian sky is (and must be) blue – just as it is here on Earth. In fact, when we used a simple color correction tool in PhotoShop called the Auto Levels tool, Mars came out looking as Carl Sagan described it after the first Viking images in 1976 – it looked like Arizona.
Now, even though we posted links to the earlier web articles showing the evidence for why Mars skies must be blue and not red, several readers apparently didn’t read those articles and continue to insist either that the color of Mars sky should be red, or that typical auto correction tools are not appropriate for this kind of analysis.
“Unfortunately this kind of white balance color correction does not prove anything. It only shows what the Martian landscape would look like on a sunny day under an Earth sky. The only thing we can know for sure about the "corrected" Martian sky in that picture is that it is wrong. Both the color chart and the landscape reflect light, which gets corrected. The sky on the other hand is direct light. The only way to know for sure what NASA has been doing is if we had some direct light source on the rover for which the light spectrum was known … The reason for bringing the color chart to Mars is not to get a corrected picture, but to be able to correct for the Martian light conditions such that the stones can be seen in their true colors as if they had been brought back to Earth. That is a smart thing to do if you have geologists working on classifying the stones. But sorry, this kind of color correction alchemy will never tell us if NASA is fooling us or not.”
“… It would make no sense that the colour of the Martian sky should be blue. The atmosphere on Mars is completely different than the atmosphere on Earth. The light is also traveling a greater distance to reach Mars. I have found the following excerpt on a page which explains, in detail, why the sky is blue on Earth. The page also used Mars as an example to explain why the atmosphere must be the correct composition to result in the bluing of the sky:
“’…Notice that this argument depends very little on the composition of the atmosphere. Any clear atmosphere of more or less Earthlike size and density, lit by a sun whose light appears more or less white, would result in a blue sky.
“’The color pictures from Mars Pathfinder are a spectacular reminder that the sky is not blue on Mars. Instead, it has colors that have been described as everything from "orange-pink" to "gray-tan", as was discovered in the 1970s by the Viking landers. This is because the atmosphere of Mars is very thin and dusty, and atmospheric light scattering is dominated not by the molecules of gas (in the case of Mars, mostly carbon dioxide) but by suspended dust particles. These are larger than the wavelengths of visible light, and they are reddened by iron oxide, like Martian soil. It's not just Rayleigh scattering, so the power spectrum is different…”
There are only three things wrong with these evaluations; they’re wrong, they’re wrong, and they’re wrong.
First of all, as we clearly establish in the color article on the Enterprise Mission web site, the atmosphere of Mars is not “dusty” -- at least not all the time. The article contains several earth bound telescopic images as well as Hubble images and one from Mars Global Surveyor which all show that the scattered sunlight from the air glow limb of Mars is categorically blue. You can see them here, here and here. The fact that they are all blue effectively eliminates the “suspended dust” argument as an explanation for why the sky is red on virtually all NASA images taken from the Martian surface. Clearly, if there was optically significant red dust suspended in the atmosphere of Mars on a consistent basis, the repeated orbital and ground based telescopic photography would reflect this. They do not.
Further, as this NASA press release explains, even the planetary scientists at NASA expected the sky to be blue in the Pathfinder images. To quote: "If dust diffuses to the landing site, the sky could turn out to be pink like that seen by Viking ... otherwise Pathfinder will likely show blue sky with bright clouds.” [emphasis added].
We can also discount the presence of this reddish dust as a factor in the red skies of Mars by using another scientific methodology; simply looking at the shadows that are cast.
If there were vast quantities of reddish dust in the sky obscuring the direct sunlight, then the shadows cast by the rocks and hills would have to be diffuse and fuzzy. In fact, if you look at the majority of NASA surface images of Mars, the shadows are distinct and sharp, meaning the sunlight is not being significantly obscured or diffused – either by clouds or the mythical “reddish dust.” This constitutes an absolute, inviolable proof (based on fundamental optical physics) that “red dust” cannot be the reason that Mars skies appear red in so many NASA processed images.
Now, as to the other statement that “The only way to know for sure what NASA has been doing is if we had some direct light source on the rover for which the light spectrum was known …” Well, we have an answer for that one too.
The fact is, we do have a “direct light source on the rover for which the light spectrum is known...”
It’s called the Sun.
Since, as we’ve already established, dust and clouds are not a factor in the rover images we have posted, then the rover itself (and the color chart on it) are being subjected to “direct sunlight.” Since the Sun is a fairly common “G-class star,” its visible light spectrum is well known (see here). So, in the absence of significant diffusion caused by red dust or heavy clouds, we can expect that the surface of Mars will look pretty much like the surface of the Earth under the same direct sunlight. Therefore, using a tool like the auto balance feature in PhotoShop to correct the color chart so that it appears as it did on Earth is a perfectly valid technique, and one which should produce results that accurately reflect what objects on the surface of Mars truly look like.
But you don’t have to take our word for it. We're not the only ones to have reached this scientifically-based conclusion.
Ron Levin is the son of Viking Labeled Release Experiment Principal Investigator, Dr. Gil Levin. The younger Levin is an MIT-graduate physicist, currently working for Lockheed-Martin, who has, independently, carried out his own analysis of the "color anomalies" seen in the NASA rover images. Ron’s story of how he almost got kicked out of JPL in 1976 for correcting the color on the public monitors is told in Dark Mission.
In one recent paper on the NASA surface color imagery, titled "Color Calibration of Spirit and Opportunity Rover Images," Levin writes:
“... images of the [rover] color calibration chart taken on Mars for the express purpose of verifying calibration seem to be in reasonable agreement with calibration images taken on Earth under Earth-like illumination conditions. However, calibration charts shown inadvertently on production panoramic images are not compatible with those images made for the express purpose of calibration [emphasis added] ...."
In other words, NASA is deliberately altering the colors of the Martian surface and sky, as an examination of the color calibration charts shows.
Which is what we’ve been saying all along here.
Levin's detailed color analysis is presented here: http://mars.spherix.com/5555-30.PDF.
So, despite what our posters would like to believe, the “suspended dust argument” simply doesn’t fly (pun intended). The only significant factor in the color of the Martian sky is Rayleigh scattering, no matter what the person quoted in the post above wants to believe.
But what about Mars atmospheric density or composition, as the other poster mentioned? Doesn’t that affect Rayleigh scattering?
In a word; no.
Rayleigh scattering is a phenomenon that is a function of sunlight’s interaction with gas molecules of a given size in a planetary atmosphere. Whether those molecules are oxygen, nitrogen, carbon dioxide or something else (like hydrogen or helium) makes no difference. All these molecules are basically the same size ... and thus will scatter blue light most effectively.
Nor does the “distance from the sun” make a difference in the spectra of light that is emanated from our Sun. The fact is the colors on the surface of Mars should look virtually identical to the colors on the surface of Earth to a human observer, because essentially the same direct sunlight is coming from the same sun and passing through a Rayleigh scattering atmosphere, exactly like it does on Earth. Only the intensity of sunlight on Mars is different because of the increased distance from the sun. The colors -- though the same -- are somewhat dimmer due to this minor decrease in total solar luminosity. But this affect is minimal: most sunny days on Mars are far brighter than an average cloudy day in Seattle, for instance.
And, as Dr. Levin points out in another paper on Mars color image calibration (http://mars.spherix.com/spie2003/SPIE_2003_Color_Paper.htm), there is yet another “proof” that skies on Mars are blue, and not red. The source of this “proof” is also unimpeachable –
It is the Rovers themselves.
As Levin points out in his second paper, the current Mars rovers Spirit and Opportunity (as well as their predecessor, the Pathfinder rover Sojourner), literally carry on their backs all the proof we will ever need that our thesis is correct. It comes in the form of the solar panels on the rovers themselves.
Unlike the earlier Viking landers, which were powered by a radioisotope thermo-electric generators (RTGs) fueled by plutonium – sort of a mini nuclear reactor -- the current generation of Mars explorers get their energy a completely different way. The Sojourner, Spirit and Opportunity rovers are powered by solar cells that convert light from the sun and sky (i.e. both “direct” and “scattered” light sources) into electrical energy. However, this energy conversion is much more efficient in a specific part of the spectral bands that illuminate Mars, the blue and the green. Red light, in fact, is extremely inefficient for this purpose compared to blue and green light, and if the skies on Mars truly as red as indicated by the official NASA photographs, this would have resulted in at least a 25% reduction in energy output from the rovers solar panels. This has not occurred on any of the missions (as determined by both direct telemetry of the minute-by-minute power-generation capabilities of all the rover solar panels, as well as monitoring of their overall power consumption curves).
As a result, we can now safely conclude that the skies on Mars must be predominantly blue, and not red.
We can further surmise that NASA technicians and engineers must certainly have known this well before the rover mission were approved, otherwise they would not have chosen to put solar panels on the rovers at all.
There is one final test which can be applied to prove the accuracy of all our technical assertions on this issue.
As it turns out, the sands of Mars are not red, as NASA has consistently asserted with their laughable color correction. In reality, the real surface of Mars tends to be more of flat yellow-red to salmon color, as many independent color corrections show. We can prove this by simply looking at some images of Mars when there is a lot dust suspended in the atmosphere – like during a major dust storm. When we examine these images, the atmospheric limb changes from a pure Raleigh scattered blue to an intense green (see here). As we all know from our experiences in finger painting in Kindergarten, you only get green by adding yellow to blue. Adding red to blue would produce not green, but purple or violet. So that means that the green scattered limb color is a result of yellowish dust interacting with a predominantly blue Rayleigh-scattered Martian sky.
What this also means is that if NASA’s color images from the surface of Mars were really an accurate reflection of a sky filled with dust, then that sky in virtually all the surface images would tend to be tinted green, not “Technicolor red.” Now, has anybody seen an official NASA Rover image with diffuse shadows and a green tinted sky, like a scene out of Forbidden Planet? If so, we’d like to see it.
So not only is our color correction technique scientifically valid, it is just one of many proofs reinforcing our most critical underlying assumption…