NASA colour conspiracy redux.

[Donn]

Hello again,
I am still finding this red-photo issue very hard to argue:

Q: Why are the lander images so red?

I have since found (on Bad Astronomy) that the atmosphere of Mars is NOT red due to scattering - because it's too thin. So, why should the colour of the lander (etc) be red-tinted?

I am not bothered by the colour, but it is frustrating not to be able to explain it to the conspiracy people.

Could one of you with laser-sharp logic please spell-out an easy to understand yet scientifically sound explanation?
Thanks again.

[Donn]

It looks like the rot might have begun here:
http://www.chez.com/lesovnis/htm/marscol.htm

I gotta get offline now, please have a look and put your thinking caps on!

[Ed]

Originally posted by Donn
It looks like the rot might have begun here:
http://www.chez.com/lesovnis/htm/marscol.htm

I gotta get offline now, please have a look and put your thinking caps on!

You never adjust RGB on your TV? Of course you do.

Two questions: So what? and Why?

[Trollbane]

The Hubble proves the sky is blue on mars got me rolling on the floor and laughing..

Anyway... My guess is that the NASA uses a film that absorbs longer wavelenghts better than short wavelenghts to avoid UVs messing up the photos.

[wayrad]

Originally posted by Trollbane
Anyway... My guess is that the NASA uses a film that absorbs longer wavelenghts better than short wavelenghts to avoid UVs messing up the photos. Nah, it's those lousy Martian 1-hour photo processing joints.

[Correa Neto]

Can I offer a handfull of hematite?

Mars`soil has a lot of hematite. This iron oxide, despite having a bluish metallic color, has a dark red trace. Small particles of hematite have this color. I see this everyday in the iron mines I work. The shovels, drilling machines, blasts, my small hammer, they all send large volumes of annoying reddish dust particles in the air. A bath after a visit to an iron mine results in towels with nasty reddish-brown stains.

Now, Mars has no plants or water to keep these particles from flying around at the slightest breeze. So, you'll have everything covered by a reddish dust. Add this to the previously mentioned effects of image proeccessing.

Funny note- depending on the iron mining province, the color of the stains change, due to the composition and morphology of the minerals that compose the deposits. Carajás results in darker stains with a deeper brownish hue than Quadrilátero Ferrífero.

[DickK]

Originally posted by Trollbane
The Hubble proves the sky is blue on mars got me rolling on the floor and laughing..

Anyway... My guess is that the NASA uses a film that absorbs longer wavelenghts better than short wavelenghts to avoid UVs messing up the photos. Hehe, not sure if you're being serious but I'll take the chance. Hubble doesn't use film, for pretty obvious reasons, and it's probably as interested in UV as any other range of the EM spectrum that reveals something useful... (see http://hubblesite.org/sci.d.tech/behind_the_pictures/meaning_of_color/index.shtml). Not sure, but that site may also provide Donn with some ammo.

[Donn]

Thanks to Correa Neto for that person insight into dust and its nature. And to the others as well.

I have taken this discussion over to Bad Astronomy and I hope to get more pointed answers to questions about how light reflects and gets absorbed etc.

As a parting shot I will post my BA question here and if anyone answers I will return.

________________________________
There is a lot of talk going back and forth about the colour of Mars and the colour of the photographs NASA supplies. I have come to this forum from the JREF forum because I hope this is the place to get a more succinct yet descriptive answer to my questions.
I have only highschool science and that over 15 years ago so I by no means clued-up in science.
I have recently been arguing with a Conspiracy Theorist (CT) about the colour of Mars' atmosphere and why the lander appears to have undergone a colour-shift, but I am at the edge of my knowledge and ability to explain.

To put it plainly, I need expert help.

My questions:
1. Earth has blue sky due to 'scattering' of blue light. If we imagine the 'air' as tiny balls and the light strikes them, what happens? Does:
(a) the white light become absorbed and only the blue reflects away? (b) The blue reflects away but the rest of the colours speed on in a straight line?
Essentially what is the difference between scattering and reflection and the colour of objects under white light.

2. Why should Mars' atmosphere prefer red and Earth's blue? Or is this wrong?

3. If the red hue is due to the red dust in the atmosphere of Mars, there seem to be two arguments:
(a) The CT approach: The red light is scattered by the red dust and thus is 'used-up', leaving only blue/green and others to get through to illuminate the lander (etc)
(b) My understanding: The red light is bouncing around the dust because the dust is reflecting it and absorbing the other colours; hence there is a majority of red light in the mix.

4. There is a CT argument that if the atmosphere was so full of this dust, why do the scenes we have seen seem so clear and detailed? Specifically, why are the shadows of/on the lander so sharp? Should they not be fuzzy with the dust acting like a blur filter over the whole scene?

5. Dare I ask? I recall there was a particle and wave nature to light. Now I wonder how to talk about what light will do in an atmosphere without knowing what the latest mind-tools are for this kind of duality? How does one discuss light and so forth without constantly switching from particle to wave etc? Just a flyer - not wanting a physics 101 course here!

Well, thanks for reading my questions, I hope you can shine a light onto my ignorance and help me to argue a CT a little further into his corner.

Donn.

[Prester John]

I think i read that the camera images are all greyscale anyway. Colour is added using filters. Some of the photos are taken at infrared wavelength. So i guess that colour is a bit subjective anyway.

[diddidit]

There is a color calibration target on each rover, incorporated into the little sundial that they use to determine local time.

http://athena.cornell.edu/kids/sundial.html

did

[pupdog]

Even to my naked eye, Mars appears reddish, certainly compared with Venus or Jupiter. So is this light reflected from the surface (and iron oxides makes sense)? How does a planet's atmosphere affect the color perceived by an observer?

[scribble]

No one else is saying it. I'll just go ahead and admit, the pictures are colored over because if we saw how beautiful Mars really is, we'd all want to go there.

It's true.

Okay, maybe not. Maybe what's true is that Mars is the ***** RED PLANET. I don't what elements it's got going on there, but it definately reflects more of the red wavelengths than the others.

When you stand outside on a sunny day, you're getting light from several sources. The sun, of course, but also diffuse lighting from the sun's rays reflected off the atmosphere and various distant objects, and the direct reflection of light off the ground and objects near you.

Now, I'm no rocket scientist, but it seems pretty clear to me that if you're on a planet with much less atmosphere than we have, you're going to lose a lot of the diffuse lighting.

Furthermore, I'm given to understand that the direct sunlight in our own atmosphere loses red to nitrogen, making everything in the world appear LESS RED than it "really is."

This leaves our MArtian scene with sunlight coming direct from the sun, with a much larger red component than we are used to. We will trivialize the effect of diffuse lighting, which also of course would have a greater red component (but exist in lesser quantites) and assume most of the indirect light in the scene comes from the immediately adjacent objects... which reflect primarily the red wavelengths.

Now... someone tell me, what's the big mystery?

[Pyrrho]

As I said in another thread, they compared one Mars photo to a photo taken in artificial lighting. Makes a world of difference. Besides, they're nuts.

[epepke]

Originally posted by Donn
1. Earth has blue sky due to 'scattering' of blue light. If we imagine the 'air' as tiny balls and the light strikes them, what happens? Does:
(a) the white light become absorbed and only the blue reflects away? (b) The blue reflects away but the rest of the colours speed on in a straight line?

White, of course, is a combination of colors. It's more (b) than (a). The scattering of blue light is one of the reasons that sunsets are red.

2. Why should Mars' atmosphere prefer red and Earth's blue? Or is this wrong?

I don't know if it does. Most of the scattering in Earth's atmosphere is do to nitrogen molecules. Mars' atmosphere is much thinner, to the point where any scattering by gases can probably be ignored.

(b) My understanding: The red light is bouncing around the dust because the dust is reflecting it and absorbing the other colours; hence there is a majority of red light in the mix.[b][quote]

This is the more accurate. Dust is generally too big to scatter the same way that gas does.

[quote][b]4. There is a CT argument that if the atmosphere was so full of this dust, why do the scenes we have seen seem so clear and detailed? Specifically, why are the shadows of/on the lander so sharp? Should they not be fuzzy with the dust acting like a blur filter over the whole scene?[quote]

That seems a poor argument. By the time you get enough dust to cause significant softening of edges nearby, you've got enough that it's hard to see the edges nearby.

[quote]5. Dare I ask? I recall there was a particle and wave nature to light. Now I wonder how to talk about what light will do in an atmosphere without knowing what the latest mind-tools are for this kind of duality? How does one discuss light and so forth without constantly switching from particle to wave etc? Just a flyer - not wanting a physics 101 course here!

This is largely unnecessary. All you need be concerned with is that different colors of light have different sizes. If you think of light as a wave, it's the wavelength, and if you think of light as a particle, it's the size of the particle. Light, of course, is neither a partical nor a wave, but it does have an amplitude, which also has a size. The idea of "wave-particle duality" represents a state of confusion about 70 or 80 years ago. We have better tools now.

[Donn]

Hello again: online at peak expense, midle of the day - must be quick.
I have not had time to read all the posts, but wanted to ask one other question:

Q: If you sent a beam of light on Mars through a prism, what would the result be? Would there be a gap in the blue spectrum?

Cheers

[Hand Bent Spoon]

...any attempt to reason with someone who thinks there is a conspiracy due to the fact they don't belive Mars is red is doomed to failiure.

Nothing like a good ol' college try, though (and furthuring your own understanding as a positive side-effect, so it's not entirely futile).

[Ed]

Ask him "why"?

[PygmyPlaidGiraffe]

Originally posted by Correa Neto
Can I offer a handfull of hematite?

Mars`soil has a lot of hematite. This iron oxide, despite having a bluish metallic color, has a dark red trace. Small particles of hematite have this color. I see this everyday in the iron mines I work. The shovels, drilling machines, blasts, my small hammer, they all send large volumes of annoying reddish dust particles in the air. A bath after a visit to an iron mine results in towels with nasty reddish-brown stains.

Now, Mars has no plants or water to keep these particles from flying around at the slightest breeze. So, you'll have everything covered by a reddish dust. Add this to the previously mentioned effects of image proeccessing.

Funny note- depending on the iron mining province, the color of the stains change, due to the composition and morphology of the minerals that compose the deposits. Carajás results in darker stains with a deeper brownish hue than Quadrilátero Ferrífero.

interesting

is the hematite undergoing oxidation in the mine you are working at?

but would hematite (provided it can be confimed that there is in fact hematite) be undergoing oxidation on mars?

I doubt there is any water-moisture or significant oxygen to facilitate oxidation.
Or is the oxidation not recent? Is there some other element that causes oxidation of hematite?

[PygmyPlaidGiraffe]

if the conspiracy theorists are correct and NASA is doctoring photos to give us the impression mars is reddish in colour on the surface and or the sky as well.....

What purpose would this serve?

What possible goal or reason would NASA have in misleading the public about light refraction on mars? Why is it so important for NASA to convince the public the surface or sky is red?

Is NASA also lying to us about the nature of light refraction on the moon? Why? to what end?

Is NASA lying to the public about the existance of sunspots and solar flares. I stare directly at the sun for 10 whole minutes a day and I see no flares.;) :p

in fact I am having trouble seeing anything anymore... why is that? Did NASA malisciously blind me with an odorless gas?

[Donn]

Hello again,
I feel like I should attach the document I wrote in reply to the Conspiracy Theorist, but I am also a little wary of doing that. I feel it's a little egotistic for some reason.
Well, I suppose that's what the whole thing is about, and I would value any responses - positive or negative (as long as they are constructive).

I hope it makes sense.

Thanks to those who made contributions.

Here goes...
(It was a zip with images and a doc file, to fit on this forum I ditched the images and converted to txt - apologies for the formatting loss)

[Correa Neto]

Originally posted by PygmyPlaidGiraffe


interesting

is the hematite undergoing oxidation in the mine you are working at?

but would hematite (provided it can be confimed that there is in fact hematite) be undergoing oxidation on mars?

I doubt there is any water-moisture or significant oxygen to facilitate oxidation.
Or is the oxidation not recent? Is there some other element that causes oxidation of hematite?

On Earth, weathering causes the hematite to become iron hidroxide. OK, being more specifical, this will depend on Eh/Ph conditions. In some extreme cases, weathering (or other surficial proccesses) may generate magnetite, for example. Magnetite can be deposited at the bottom of lakes with a highly reducing environment. Oops, sorry for the OT drif.

If I'm not mistaken, the presence of hematite in Mars has been confirmed by spectroghaphy. If this information is correct, then we should ask ourselves how it has been formed- by what types of internal and external procceses. The age is surely open for discussion.

The avaliable images of Mars show a landscape that is dominated by physical weathering. Sure, the ammount of water and oxigen on Mars is quite small when compared to Earth, and there is also the lack of plants- a great incentive for weathering). But there is some soil in the pictures. Was all this loose material generated by physical weathering, volcanic tuffs and meteoritic impacts ejecta? Or some chemical weathering also helped on its formation? I think some chemical weathering may have existed (and perhaps is still active, at a reduced level when compared to Earth).

On a purely hypothetical basis, sitting at a pub while drinking beer, I would say that some degree of chemical weathering must still happen in Mars, maybe due to the interaction of CO2 with the minerals. The presence of "morning fog" in some pictures and the evidence for some water, even if on the subsoil, adds an extra element for chemical weathering. Even small ammounts of water on very cold climate may generate chemical weathering, as long as you provide enough time (but do not expect the 200 - 300 meter-deep weathering levels we find at some places here in Brazil). There is also the possibility of presence of clay minerals on Mars (remember the Viking experiments?). Clays are also typical weathering products. If the environment is oxidizing, the clays will be reddish, adding more annoying red dust. Carbonates were fond on the landing sites. Carbonates, as hematite, can have several origins, weathering being one of them, adding another cirscunstantial evidence for chemical weathering. Note that basalts are rich in calcium silicates.

Hematite can be generated by several processes, internal and external. Hydrothermalism, metamorphism, chemical deposition, weathering. On Earth, chemical deposition in sedimentary basins when there was little free oxigen in the atmosphere generated massive iron deposits (composed by hematite and magnetite- there are discussions regarding which one was the deposited mineral; personally I think both were, it depended on Eh/Ph contitions at each basin- sorry, I'm drifting again). If Mars ever had bodies of water, this would be a possibility. OT drift no. 3- some researchers link deposition of some of these banded iron formations to microscopic algae and bacteria. Some old microfossils come from such sources (OK, as always, there are controversies).

I belive, however, that the massive basaltic flows are a more likely source. Some of the magnetite, iron and calcium silicates could be turned in to hematite, clay minerals and carbonates by weathering, reacting with water or CO2 (see above). These minerals could then be scattered throughout the planet by winds. Remember that there is no vegetation or moisture to keep the dust-sized particles on the ground.

[Donn]

I have his reply, if you want to read it. He still votes for a blue sky on Mars and I cannot argue with him becuase I do not know enough.

One of his statements is that if blue is removed from the spectrum the resulting colour is yellow NOT red; which could be perfectly true; I just do not know!
______________________________________
Hi Donn,

Thanks for your response. I found it interesting.
It seems you have put considerable effort into all this.
The links below affirm the fact that the colour of the Martian sky can be non-other than blue.

It appears that NASA have NOT, from the evidence at hand (essentially 'proven' by Keith Laney's processing - see below), been 'changing' the colours; but they most certainly HAVE been mis-representing the colours pictures to the public by incorrectly combining the colour channels from the
Pancam sources.

Of course, I agree with you that the Martian sky, like that our planet, can change depending on conditions; however, the Martian sky is generally a rather light blue (as could be expected, due to it's thin atmosphere) as is proven by the (truly) True Colour pictures composed by Keith Laney, the
NASA/Ames image processor, as taken from NASA's own original data (no, it has not been modified by Keith):
http://www.keithlaney.com/spirit_color_images.htm

Here Keith explains the process, very clearly as far as I'm concerned, of obtaining True Colour images from the raw NASA feed: http://www.keithlaney.com/spirit_color_images_calibration.htm
His processing of the colours in the correct way makes complete sense to me and I don't know why I didn't think of this in the first place (maybe because I'm not a space image processor *LOL*).

The reason the sky looks blue', and these are NASA's own words:
"The visible violet light has a wavelength of about 400 nm. Within the visible wavelength spectrum, violet and blue wavelengths are scattered more efficiently than other wavelengths. The sky looks blue, not violet, because
our eyes are more sensitive to blue light (the sun also emits more energy as blue light than as violet)."
(Hence this should apply to ANY planet with an atmosphere, such is the case with Mars.)
See:
http://eosweb.larc.nasa.gov/EDDOCS/Wavelengths_for_Colors.html

I really don't wish to see this kind of thing turn into an argument and perhaps it would be a good idea for us to sit down and discuss it sometime.

To keep things objective, I have to point out one or two erroneous conclusions you have put forward in your response document:

'Point 2'
"The dust, some of the particles being large enough, reflects the other colours and because the blue (And others? Unsure.) has/have been subtracted this causes a general scattering of red - such that wherever you look there is a supply of red light. I emphasize this because the red light is not
"effectively removed" at all; no more so than blue light is removed from Earth's sky by Raleigh scattering."

Specifically, I am referring to the statements, "These have a special effect on the higher-frequency wavelengths, they absorb blue light.", and (this),"causes a general scattering of red". -This is simply NOT the case: An absorption of Blue would cause a reflection (and some scattering) of Yellow, NOT Red-

Also, I do not see how you can say that it is a fundamental mistake to say that, "The secondary effect of the dust particles would be one of scattering the incoming light, and thus causing objects on the ground to appear turquoise (or 'bluish') by effectively removing the red component from the
direct light." I would certainly say that my wording here is perhaps NOT 100% accurate, and for that I apologise, since I do NOT intend to imply that ALL of the 'red component' from the direct light is removed. I would say, however, that a large percentage would potentially be removed, depending on the degree of scattering, in the case of having a 'red-scattering' Martian atmosphere.

I certainly do NOT mean to imply that the Red light which would be scattered in this case will NOT reach the surface; it will, however, reach it in diffuse form (the degree of which would depend on a number of factors).
This would effectively mean that one could expect to see Red shadows (of
varying degrees, of course, depending upon the variables).

You asked me to show you a link to show you that the incoming light on Earth
has a Yellow-tinge, as I asserted earlier. I did a quick search and found
this http://www.atmos.umd.edu/~ezra/whyblue/whypaper.html which you might want to
look at. I quote from it: "Since a lot of the blue light is no longer in
the original direction, the remaining light becomes more yellow."
An extension of my statement that the direct sunlight reaching the Earth's
surface is tinged with Yellow, and something which I did NOT want to get
into earlier since it is diverging from the point of the discussion, is that
due to the direct Sunlight on Earth having (some of) the Blue spectrum
removed from it one can expect all terrestrial shadows, especially at Noon,
to be Bluish (which they ARE, but we do NOT notice this since the direct
Sunlight is way too bright and creates too much contrast). The Blue shadows
on Earth are, of course, due to the diffuse Blue light scattered in the
atmosphere. The fact that the direct Sunlight illuminating everything on
the surface of our planet is in fact Yellow light is something that most
people are NOT aware of since our eyes are naturally adjusted to this
'natural' light.

It is important for us to distinguish between Raleigh Scattering and dust
particle scattering, and do NOT think that either of us have been clear on
this. One thing that has become clearer to me is that Raleigh Scattering
occurs due to the fact that Blue (and violet) light scatters much easier
than do the other colours in the spectrum (this re-affirms the point that
virtually ALL planets with atmospheres will exhibit Blue light Raleigh
Scattering).
Dust particle reflection (of which scattering is a secondary effect, though
they can be argued as being one and the same in most cases, I believe), will
of course, affect the general 'ambient' (diffuse) colour of it's
surroundings and align it with the particular colour spectrum reflected by
the particles (i.e. 'Yellow dust', especially in the lower atmosphere, will
have an effect of causing objects on the surface to appear more 'Yellow', if
the particles are in close proximity to the surface and their density is
high enough).

This is straight-forward physics and it needn't be as complex as some people
believe it to be. We should keep the fundamental Light Spectrum physics in
mind when we look at these things, and it is indeed very simple: Absorption
and Reflection of varying wavelengths of light - that is all that is going
on here - Subtraction and Addition - there is NO 'in-between'.

The statement quoted by someone in your Response document, "The reddish
particles PREFERENTIALLY ABSORB BLUE LIGHT and effectively act as mirrors by
scattering the remaining wavelengths: the color of the atmosphere is
therefore pinkish, like the particles themselves", is incorrect since the
'remaining wavelengths' would form Yellow, NOT 'Pink' or even Red; unless
they absorb the Turquoise (Cyan) colours, which is probably the case. So,
the Limonite is absorbing the Cyan wavelengths? Ok, so then Red is being
reflected and scattered, which would mean that we could have a limited 'Red
colouring' of objects on the surface; however, this will remain very limited
and will be DIFFUSE in nature which would mean that the Direct Sunlight
coming through will create too much of a contrast of Pure Light in order to
distinguish it since the Direct Sunlight is by far much more intense than
the reflected (diffuse) light created by the Limonite. If this were NOT the
case (where we have Greater Diffusion than Direct Light), we would see
badly-defined shadows on the surface.

Anyway, I think we now have our answers as to the True Colours of Mars,
thanks to Keith Laney.

------------------------------
Over to you!

I am off to find sites concerning colour and so forth. Hope I find better info this time round.