"What is it?" - gasped at that time the American Losers, who could not read the descriptions under the photo - "Why is the NASA emblem burgundy and not blue?"
And really why? NASA will not be so stupid to be fired up: to hide the true color of Mars (let's bypass the question of what for it is generally necessary), and at the same time leave color clues that any conspiracy theorist could expose the conspiracy.
But all you had to do was look at the description of the photo and find out that these shots were made using not a red filter, but an infrared one. The color photographs on the twin rovers were created by shooting with a black and white camera through different color filters. There, on each camera, there were seven filters with different wavelengths, slightly different on the right and left, among which was red and infrared.
More about getting color images from rover cameras: written a long time ago.
A bit of theory: a color frame is obtained if you shoot through three filters: red, green and blue (RGB format: red, green, blue), and then combine three frames in Photoshop to get one color.
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In some cases, NASA used infrared rather than a red filter. This was necessary in order to obtain extended information about the properties of the soil and the objects under study. After all, the rover's camera is first of all a scientific device and only then a means for the entertainment of taxpayers. So the panorama with the Spirit landing platform was filmed using an infrared filter. But at the same time, the Opportunity platform was filmed using red and in normal colors, which is evident from the difference.
The NASA emblem is not visible, but the blue duct tape ™ catches your eye. But if you look at the difference in the ground in these two photographs, then it is not so significant. It is "redder" through infrared, but you still can't see the original green grass and blue sky.
The peculiarity of obtaining color images through three filters has caused another accusation from NASA that they post a lot of black and white images and very few color ones. Firstly, “few colored people” is nonsense, because Even before Curiosity, thousands of Spirit and Opportunity color shots were published, and dozens of huge 360-degree panoramas. Secondly, by uploading raw black and white footage taken through color filters, NASA gives everyone the opportunity to make their own color images of Mars. But conspiracy theorists master Photoshop only up to the Autocolor function, with which they "restore the true color of Mars", and the subtleties of working with color channels are unknown to them.
The next argument of the adherents of the "Mars Red" doctrine is a BBC report on the work of NASA specialists. According to the plot of the program, the scientist is sitting at a working laptop, then journalists enter his office, and they ask something there.
But the conspiracy theorist screams "Aha!" and pokes at the monitors behind the scientist's back, and there is not red Mars and blue sky. At the same time, the organization of conspirators of a global scale looks more than strange, where journalists with cameras calmly walk around the offices, looking where they like. But those who dream of catching NASA in a lie do not think about it.
So what's on that monitor? It shows the Cape Verde site of Victoria Crater that Opportunity explored.
NASA scientists are using processing under ground lighting conditions to make it easier to identify rock rocks that are encountered by rovers. Since the eyes of geologists are accustomed to terrestrial conditions, the change in the color scale of Martian images is made in the same direction. And these photos are not at all secret.
Here is Cape St. Mary next door to Cape Verde
And this is generally a vigorous Cape St. Vincent.
Or the Santa Maria crater that Opportunity passed last year
This photo was taken using 13 color filters.
Can you imagine what would happen if journalists caught a scientist editing this photo? "NASA is hiding that the rovers have landed on a rainbow!"
It's just that the published photos always indicate the type explanation: It is presented in false color to accentuate differences in surface materials. Or in the case of this rainbow photo: The image was taken by the panoramic camera on NASA's Mars Exploration Rover Opportunity using all 13 color filters. But those who see traces of a conspiracy everywhere cannot read.
In addition, the conspiracy theorists, apparently, are not aware of the existence of dust. Otherwise, they would not have taken this photo as another proof of the NASA conspiracy.
This is a memorial flag placed in memory of the victims of 9/11 on the Opportunity manipulator. And attention is drawn to the fact that it seems as if it is tinted in red. Conspiracy theorists think this is proof of the use of a red filter, even though it's just red Martian dust. The frame was taken in 2011, and if you look at the photographs taken in 2004 at the beginning of the research operation, for 31 sol (Martian day), then there is a clean flag in the colors we are used to.
When Curiosity's large self-portrait appeared, some also tried to look for traces of a conspiracy there.
"Something NASA emblem is kind of gray, but it's blue" only they also forgot about the dust. Landing of MSL was carried out not with the help of inflated cocoons, as in previous rovers, but with the help of Sky Crane, so that it was made in the dust from the first seconds on Mars.
UPD. Brushing applied to the surface of Mars showed its natural color
They also tell a story about how the first image of Mars was taken from the Viking 1 lander.
The book, the authors of which prove that there is life on Mars, and NASA hides it (Mars: The Living Planet, by B. Di Gregorio, G. Levin and P. Straat, Frog Ltd, Berkeley, 1997) provides a story about the circumstances of obtaining first shot. According to their testimony, the JPL gathered journalists, placed color televisions everywhere and, having received a picture from Mars, immediately displayed it on the screens. The photo allegedly had blue skies and green spots on the rocks. After that, as the description in the book says, NASA specialists ran from monitor to monitor, twisting their color setting so that the photo of Mars was in red. It is no longer possible to verify the reliability of this story, but there are two indicative points: firstly, the Viking color frame was obtained in the same way as on the twin rovers - by combining three black and white images,therefore, there was no signal from Mars that would have to be immediately displayed on monitors; secondly, if an image from a neighboring office was broadcast on the monitors, where the color mixing of the frame was performed, then wouldn't it be easier to replace it with “red” and continue broadcasting than to attract attention by adjusting the monitors in front of everyone?
Thanks to the hysteria whipped up by conspiracy theorists, many began to worry about the question: what color is Mars and the Martian sky really? Let's figure it out.
The main culprit for the red color of Mars is iron oxides, or just rust. The Martian crust was found to be very rich in iron ore. For example, the Meridiani plateau, where Opportunity rides, is simply strewn with hematite - iron balls formed in shallow water bodies or groundwater.
When exposed to water in an oxidizing atmosphere, iron turns into rust, which, as those who work with metal can know, easily becomes a fine fine dust. And there was once a lot of liquid water on the planet and for a long time, so Mars had time to turn red. According to NASA observations, all dust on Mars is magnetic, i.e. contains iron impurities.
Martian storms carry dust even where there is not much iron in the ground. For example, in Gale Crater, at the Curiosity landing site, the lander's jet jets blew off dust, revealing a gray surface.
But in a matter of days, everything returned to the usual red-haired picture.
But in general, the landscapes are lighter there than on the Miridiani plateau.
Likewise, the rover itself was covered with dust, therefore, examining its color markers and hull, or trying to restore its "true color", it should be borne in mind that there is red Martian dust on it.
I don't want to touch on the subtleties of white balance color calibration here. We tried it somehow, but I'm not happy with the results and I'm already used to the raw colors of Curiosity.
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I will just say that Curiosity color cameras, unlike their predecessors, have a standard color Bayer filter on the Kodak KAI-2020 CCD matrix, so they shoot like ordinary SLR cameras. The difference in color rendition depends on the white balance setting. But on Earth, camera color balance adjustments were made by people who knew what a particular color would look like at a given color temperature. There have not been people on Mars yet, so there is no one who could say "This is the correct color" and slight variations in color take place. For supporters of the theory that NASA is shooting everything through a red filter to hide green Mars, I will share a secret that in raw images of Curiosity there is just a slight inflection in yellow-green.
The way Mars looks from space is much easier. We have photos of "Viking"
Hubble
Mars odyssey
If someone does not trust NASA, they can look at the images of the European satellite Mars
The photo at the beginning of the article is also his.
Or a beautiful true-color photograph of the European satellite Rosetta
(Round "horseshoe" slightly to the left and below the center - Gale crater)
Or even the Soviet Mars-5
The latest satellite MRO shoots in extended colors, so its footage cannot be called "true", it looks like a light gray like ultramarine, and a dark gray like a deep blue. But I recommend everyone to go and admire the photos on the official website.
Upd. Two years later, after writing the article, you can add another Mars from the Indian Mars Orbiter spacecraft:
But with the Martian atmosphere and the color of the sky, it is more interesting. If we turn again to the Hubble images of Mars, many of them show the blue atmospheric envelope of Mars.
For conspiracy theorists, this is proof of a Martian conspiracy, they say, that's proof of the blue Martian sky. Proponents of this idea forget that both Hubble and the rovers are operated by the same NASA Jet Propulsion Laboratory (JPL). Therefore, it looks strange that they calmly publish dirt on themselves. But logic and conspiracy have never been friends, so let's continue.
The problem with the Martian blue atmosphere is that it's too thin. The atmosphere of Mars makes up 1% to 0.75% of the Earth's atmosphere - seasons affect density. The pressure on the surface of Mars is the same as at an altitude of 30-40 km above the Earth. Accordingly, the sky there should be the same. When Felix Baumgartner jumped, everyone could see what kind of sky there was on a clear day.
Or, recently, the Spaniards launched a prototype of a tourist stratospheric balloon at 32 km
But there is no black sky on Mars either. So what's the deal? And the solution is in the same Martian rusty dust. It is very shallow, dry, and the gravity there is three times weaker, thanks to this dust can climb quite high even when there are no dust storms. On Mars, even clouds are of three types: water (from ice), carbon dioxide (also ice) and dust.
Thanks to the dust, the color of the Martian sky has different shades from pink to beige, and in a storm and brown. Moreover, in calm weather it darkens noticeably towards the zenith.
(Survey Viking1 Lander, sol 1742 - dust storm)
At the same time, at sunset and sunrise there is a unique chance to see the blue sky of Mars
The color of the sky on Earth depends on Rayleigh scattering. The short-wavelength part of the spectrum from violet to blue is scattered in the air, coloring our sky. When sunlight passes through a thicker layer of air - at sunset - longer waves, up to red, are also scattered, which is what we owe to our red sunsets. On Earth, sunlight near the horizon passes 38 times thicker air than at its zenith, and comparable scales can be imagined on Mars. But there, this thickness only allows you to see the blue in the sky, like we have on a clear day, and even then only around the disk itself. And only the violet wave has time to dissipate a little further.
Unfortunately, Curiosity has not yet captured sunrises and sunsets, but there is an explanation for this. Unlike previous rovers that worked on the plain, Curious is in a deep crater. It is surrounded by mountains, behind which the sun hides without having time to dim until the moment it can be shot without a solar filter without fear of damaging the camera matrix with too intense light.
Maybe the danger of such a light would not be fatal, especially recently, when a local dust storm was taking place, but NASA is reinsured and removes only through the "welding mask".
(black dot is Deimos)
That's when Curiosity climbs the mountain and is able to look beyond the crater, then there is a hope to see a sunset or sunrise in high quality, but wait for this for at least a year.
In conclusion, I would like to say that the color of Mars is almost the same variable indicator as on Earth. There are no oceans and green spaces on Mars, but the time of year, time of day, weather, geological structure of the surrounding rocks affect what colors will be in a particular area at one time or another. Blaming NASA for a conspiracy is a pointless affair, if not for it we would still be drawing Martians sailing in their junks along the canals along the rice fields. Of course, there was a Soviet research program, there is Mars Express, but 90% of the information we know about Mars is thanks to NASA. And in order to check the reliability of their information, it is enough to know the school physics course and be able to read.
UPD:
Just three days after the publication of this post, Curiosity sent in a survey of the Martian sky at its zenith. Shooting for Sol 101, when the rover was covered with distant echoes of a dust storm. Visibility has dropped from 30 to 10 km, but the zenith is still darker. The white edge to the left is from the proximity of the Sun.