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On the perception of the colours of Mars…

I was looking at a post about the relative proportions of various planets today and it reminded me of a thought I’d had a couple of years ago and hadn’t ever explored in depth. It was based on a stupid theory of mine that I’d like you guys to disprove or correct or support. To start off with, look at the following picture from the above link:

So the most notable thing about this picture from my perspective (other than the size differential) is the difference in colour. More specifically, not that the colours are different, but that non-Earth planets are much more monotone. So my theory goes like this – we evolved on Earth, it’s important for us to be able to distinguish between certain types of substances and so our eyes are set up to better distinguish between the specific wavelengths of light that things on our planet reflect. Not a great moment of insight, I’m sure you’ll agree. Pushing it further though – this suggests that if we had evolved on Pluto, Jupiter or Venus, we’d perceive different wavelengths in more depth and with more variety. In fact, potentially if we’d been born on Mars, it would look to our eyes like a vibrant and colourful place, while Earth could look comparatively drab.

This could all be total balls for all I know. But what I wanted specifically to do was to get an image of Venus or Mars or whatever and kind of stretch the spectrum of colours across our visual spectrum, with the assumption that you’d get more Earth-like shades and a different sense of the landscape, even if (to the natives of this world) blue would no longer correspond to water. I’m assuming that someone’s done something like this before, but I can’t find anything good online about it, or a way to do such a thing in Photoshop. Anyone got any thoughts?

29 replies on “On the perception of the colours of Mars…”

I’d be interested to see any results. This reminds me specifically of a short story about colonising Mars where the native-born children start producing art that looks drab and horrible to their parents, but proves that they have learnt to truly see their new landscapes.
Colour perception is a complex subject, though, and combined with evolutionary theory, there are a lot of options.
Other theories would suggest that colour separations (and the need for eyesight to match) are at least in part driven by life processes themselves, rather than by evolving to view a passive unchanging external environment.
Or to put it another way, once creatures had evolved eyes to perceive light, the evolution of different coloured pigments was an obvious and inevitable step for pretty much anything that was going to be looked at on a regular basis.
I am not sure how much of the Earth’s colour variation is actually driven by life here though – anyone know?
For your theory, you get half a vote for “balls” 🙂 I’ll reserve judgement on your second half until I’ve seen some more responses!

Tom, you’re a freaking genius (seriously). I wondered about the planet colors too and never chased the thought down so far.
I’m sure that’s right. You don’t even need to go to Photoshop, I’d wager — just think about the evolution of vision on Earth, e.g. bats hunting in low light and using echolocation.
But like you, I’m understudied. Will be waiting for one of the people who wears white coats to post with authority…

I was going to say that there was more difference, physically, objectively, between the Earth’s blue and green and yellow than, for instance, the reds and yellows of Venus and Mercury on your picture.
Then I loaded a color spectrum image to check and — wow, the wavelength difference is not that large. So maybe, if we grew up on Mars, we’d find red/orange/yellow as different as we do blue/green/yellow.
But, on the other hand, all three primary colors are present on Earth, and not on the other planets. I’m not quite sure what physical properties make them primary, but I’d wager it’s likely to be a hard fact, and not just our perception.
(What’s pretty sure, though, is that living on a red planet we’d see infrareds. And maybe we wouldn’t see blues at all. So, yes, at least on this respect, Earth would look to us as dull as the other planets look from our point of view.)

According to Wikipedia (which is – I’ll accept – open for debate), “Primary colors are not a physical but rather a biological concept, based on the physiological response of the human eye to light. Light represents a continuous spectrum of wavelengths, such that being “primary” is not an intrinsic property of the color itself”
So that’s pretty cool. In a way you might say that the fact that all three primary colours are highly visible on earth is a symptom of us having evolved here – more proof to the hypothesis!

This is definitely interesting me, so it looks like I’m going to have to have a go too. There goes today’s workload!
Anyway, the way I see it, it’s just like adjusting contrast on a b&w image. You ‘stretch’ out the brightness of each pixel away from the average so that the difference between pixels increases. Of course, pixels that were already fairly close to black or white all end up completely black or white.
So, in colour images each pixel is a 3D value, either RGB or HSV (hue, saturation, brightness). Now hue is the ‘colour’ of an image and is a circular value, measured as an angle (so you go from red to green to blue back to red very smoothly). I’m thinking if you had a histogram of the hues of an image, you could work out which section is basically ’empty’, and then stretch the hue of each pixel away from the average hue so that the empty section is filled-up.
Simple, right? err…

This is definitely interesting me, so it looks like I’m going to have to have a go too. There goes today’s workload!
Anyway, the way I see it, it’s just like adjusting contrast on a b&w image. You ‘stretch’ out the brightness of each pixel away from the average so that the difference between pixels increases. Of course, pixels that were already fairly close to black or white all end up completely black or white.
So, in colour images each pixel is a 3D value, either RGB or HSV (hue, saturation, brightness). Now hue is the ‘colour’ of an image and is a circular value, measured as an angle (so you go from red to green to blue back to red very smoothly). I’m thinking if you had a histogram of the hues of an image, you could work out which section is basically ’empty’, and then stretch the hue of each pixel away from the average hue so that the empty section is filled-up.
Simple, right? err…

The one big thing that you haven’t mentioned that sets apart Earth from the other planets is that most of its surface (the blue part) is liquid water. I imagine that the Mars that would have supported the evolution of life would also be one with a more varied color palette due to having honking big oceans. Or lakes, at least. Earth without oceans would be pretty drab brown overall, I think.
With Venus, you’re not actually looking at the surface at all — you’re looking at a big cloud. Visibility on the surface is pretty lousy, I’d imagine (maybe something like being inside what we think of as Jupiter — swirling, opaque gas and vapor).
On Mercury, I’m not sure having eyes would be a benefit, since there’s so much light. Or would it? I’ve read that one side is mostly liquid (molten) while the other is kinda cold.
Anyway, on Mercury or Venus, it seem like there’d be more value in having senses other than vision. Jupiter and Venus seem natural environments for echolocation, actually, and by that standard Earth would be very bland — thin atmosphere, nothing floating around, calm weather, largely homogenous atmosphere, relatively flat surface (very flat if you’re counting above the water as “surface”). Even below the oceans I think there’s topography on Mars that makes the Marianas Trench & Mount Everest look like termite mounds. To a sonar-using species, we’d be a pretty boring planet overall.
(Might be prudent to ask a dolphin for confirmation, though.)

Interesting hypothesis. I have no idea if it’s correct or not. But I would point out that Earth is absolutely teeming with life, while to the best of our knowledge the rest of the planets are completely dead. Water accounts for the white (cloud) and blue (oceans). Life accounts for the green. Discarding those you’re left with a planet that looks to me no more colourful than its neighbours.

You’ve got it slightly backards — our eyes are not adapted to the colours on this planet, our eyes have adapted to the strongest wavelength of light put out by the sun.
The visual spectra our eyes see is 740nm (red) through 380nm (violet) (src: http://en.wikipedia.org/wiki/Color). As you can see here (http://casa.colorado.edu/~ajsh/colour/Tspectrum.html) this the peak area for energy emitted by the sun (and fairly clear we’ve adapted for this makes us see the best).
Thus, no matter where you evolved in the solar system, if your light comes from Sun, you’re probably looking at the same roughly 1-octave colour range that we currently have.

You’re somewhat right.
A graph of the average human eye’s sensitivity to light at each wavelength (colour) looks remarkably similar to the spectrum of light that passes through Earth’s atmosphere unabsorbed.
So if the atmosphere was differently composed, our eyes would most probably have evolved differently, and we’d see colours differently.
Don’t forget, though, that the spectrum doesn’t stop at red and violet. Other animals can see infrared and ultraviolet light (I have no proof for this other than ‚ÄúI read it somewhere‚Äù).
David Janes: ‚Äúour eyes have adapted to the strongest wavelength of light put out by the sun‚Äù …that isn’t absorbed en route to our eyes.
But, yes, the colours we see are mostly governed by the black-body spectrum of a 5800-K object (i.e. the Sun).

thanks for the fascinating post and comments! i’m writing a mars novel so i’m loving any discussions around human experience on mars. this gives me more to mull over.
the story neil slater mentioned is by ursula le guin. i don’t remember the title, though, and i’m not sure it takes place on mars.

Colour scientists make a useful distinction between spectral power distribution (how much energy is present at each wavelength of light) and colour (the subjective impression that the SPD makes on a human). Colour, in this sense, is influenced by context, brightness adaptation, medical issues, and the like.
Even seen from space through miles of air haze, Earth has more varied SPDs than most other solar system bodies. It’s intriguing to hunt down NASA’s real-color images. You’ll find all the planets pictured in the original post have inexcusably amplified saturation; worse, Venus is actually a radio-spectrum image dyed orange. In visible light it’s a ball of buttermilk. Garish Io?Pallid.
But even if the variety of SPDs is less on other planets, could they nonetheless appear vivid to the natives? Sure. I think it’s perfectly likely beings developing there would evolve to make the best use of what was available to perceive.
The hitch is that last clause. Dogs, for example, evolved here yet see poor colour. They get their satisfaction with great olfaction. Suits them.

Ah, thanks Greg. I was actually going to mention that for Venus since the absobption there obviously is much higher because of the continous cloud cover. May be interesting on the gas giants too where splash-back light from below you may be an important part of your environment.

– With dogs, I expect the main part of their sensitivity is still in the visible light range.
– There’s probably some evolutionary pressure to keep sensitivity within one octave; maybe something to do with harmonics?
– Now that I think of it, I bet there’s some interesting studies to be done on the light ranges seen by sea creatures…

Visible (to humans) light levels on the surface of Venus are roughly equivilent to twi-light, or a heavily overcast day. We could see there without assistance . . . but of course wouldn’t last long enough to appreciate the view.

Here’s something to try with Photoshop. This perhaps produces the effect you’re looking for
1. Copy and paste a picture of a planet into Photoshop (use the one at the top of this page, or find another)
2. Optionally, select one planet (use a circular selection), so you can see the results more clearly
3. From Photoshop menu Choose Image -> Adjustments -> Levels
4. Select one channel at a time, R, G, then B (but not RGB)
5. For each channel, look at the levels graph in the Input Levels section.
6. Adjust the leftmost and rightmost sliders under the graph. For Mars, etc, you’ll see that the peaks in the red graph stretch all the way across, but the blue and green only occupy a limited area on one side. That’s because there isn’t much blue and green on most planets.
Move the sliders so they bracket the ‘main’ section of the levels graph, and cut off the empty bits of the graph on each side. Hope this makes sense when u look at it…
What this process does (I think) is to stretch out the limited amount of blue and green in (for example) the Mars image, so it expands to occupy all of the range of blue and green levels that our eyes’ are sensitive to.
Assuming that’s correct, perhaps that’s how an eye which evolved on Mars would perceive things… Sensitive to very small variations in blue and green…
Anyway, whether it’s ‘scientifically-correct’ or not, it does make the Mars image look rather earth-like.

If we look at animals that see in IR or UV, they have a large visual range in environments that to us would look fairly monochromatic, such as deserts (scorpions, for instance are clearly distinct from their environment under UV lights).
Also, an organism can have a given spectrum’s colors ‘added to’ by the addition of a photopigment that is sensitive to a slightly different wavelength of light. In fact, since the X chromosome carries the relevant genes, some women do have an additional, variant green photopigment gene (tetrachromacy). What this means is that they can distinguish between shades of green that would look the same to those of us with who are trichromatic.
Other animals (such as birds) have even more color receptors for the same spectrum, and thus can distinguish an even greater range of colors.

This objection is either devastating or fatuous, I haven’t decided which yet.
The problem with the theory is that no human being ever saw the Earth from that perspective until about the 1960s. In other words, telling blues and greens apart (more than yellows or whites) isn’t that helpful a skill if you happen to be raised in the Sahara Desert or in the Yukon.
The theory that makes more sense is that since Earth is around the location from the sun that allows both hot and cold to take place — water can freeze or boil on Earth (not true on Mercury or Pluto) — that means that the activity is going to be much more interesting — and colorful.

David Janes says:

– With dogs, I expect the main part of their sensitivity is still in the visible light range.

On the vision of dogs. They can see better at night, but their eye structure is such that the average dog will have 20/75 vision (they can see at 20 feet what a human can see at 75 feet) — and they see substantially fewer colors:

Dogs and most non-primate mammals have only two kinds of cones. In dogs these cones have peak wavelength sensitivities in the yellow-green and violet range. Dogs can see two basic color groups, red-orange-yellow-green and blue-violet. All the colors within these groups appear the same. But dogs can tell the difference between the two groups and can tell the difference between the two groups and white or gray.

You might be more interested in the two adjacent entries here, on interconnected.org — one linking to images showing what a terraformed Mars would look like, and another with a number of links about how dogs perceive the world.

… I bet there’s some interesting studies to be done on the light ranges seen by sea creatures…

Here’s something on a NOAA project studying colors underwater while trying not to blind the creatures they’re studying.
Other links on different kinds of vision:
How shrimp eyes change in color sensitiviy depending on depth, and how deep sea crabs lose color vision (and eventually, replace light vision with heat vision) as they grow up.
And Wikipedia on cetacean brains:

The dolphin’s dependence on speedy sound processing is evident in the structure of its brain: its neural area devoted to visual imaging is only about one-tenth that of the human brain, while the area devoted to acoustical imaging is about 10 times that of the human brain. (This is unsurprising: primate brains devote far more volume to visual processing than almost any other animals, and human brains more than other primates.) Sensory experiments suggest a high degree of cross-modal integration in the processing of shapes between echolocative and visual areas of the brain.

In other words, dolphins really do “see” sounds.

If we look at animals that see in IR or UV, they have a large visual range in environments that to us would look fairly monochromatic…
I think the reverse can be true as well. At school we were taught that coral reefs are a multitude of brilliant colours even though fish can only see in grey scale. Turns out that the best way to achieve a variety of grey hues is to use colour… much the same way that silent movie stars wore garish coloured makeup which ended up looking normal when viewed on black and white film.

I think what you’re talking about is simply a corollary of the anthropic cosmological principle, which basically states that the reason that we view the universe in the way that we do is that if it was any different, the conditions for life wouldn’t exist. For example if the charge on an electron was different by 1-zillionth of a degree, all matter would be unstable, galaxies, stars and planets could not accrete matter, and what we call space would be at best a formless miasma of unstable radiation.
Similarly, if the conditions for water (and the colour range brought about by its interaction with the visible portion of the electromagnetic spectrum) were not there, then the eye could not exist, let alone evolve to view certain wavelengths.

I think this is just a corollary of the anthropic cosmological principle, which in its simplest form states that the universe is constructed as it is because if it were otherwise, we wouldn’t be here to see it. For example, if an electron’s charge was different by 1-zillionth of a degree, all matter would be unstable, galaxies, stars and planets would not form, and the space as we know it would at best be filled with an formless miasma of electromagnetic radiation.
Similarly, if the ball of rock you live on happens to be too near the sun, or be too heavy or light or consisting of the wrong stellar stuff in the first place, meaning the conditions for life are not present, specifically the presence of water in a liquid state (and consequently its interactions with the visible portion of the electromagnetic spectrum that create the blues and ultimately the greens you speak of), then the eye as we know it could not exist, let alone evolve to view the chromatic scheherezade of our water-filled world. That doesn’t rule out some silicon-based lifeform on Pluto evolving an innate EM detection facility in their antennae, but would that be sight as we know it?
So in summary, for me (a lapsed Astrophysicist): Balls.

er…or it could be what I call chinese ppl syndrome / little brown ppl syndrome / white ppl syndrome / blacks syndrome….hang on i’m gonna explain : )
It basically means: if you are not familiar with a certain group, it’s hard to distinguish between them. Till I spent some time in australia, I had barely any contact with oriental people – and couldn’t tell a korean from a japanese – I even had a hard time telling the orientals in my class apart for the first few weeks.
My sister had the same problem with white people, the first time she came to europe on work. My husband (german) often got confused between characters while watching bollywood films (i’m indian). Several folks will say “blacks all look the same” – they usually come from regions with hardly any / no black ppl.
So – the only reason we can’t (or don’t bother to) make up shapes and (more) separate hues on foreign planets is – we just don’t get to see enough of them. I think it’s as simple as that.

This reminds me of the age old question of whether my green is your green or whether your green is my red.
I mean who knows…if there was something in the brain which switched the perceived colours how would we know what colours we all see? We can agree that an orange is an orange but how do we know that the colour orange in your mind is actually more akin to the colour blue in my mind?
Freaks me out just thinking about it…

In other planet, we need to measure the visible light colors(vibgyor) wave length one by one.
As per my assumption infrared is our earth’s color.
we can’t able to see infrared color in spectrum, when we are staying in earth.
But if we will stay in mars, we can’t able to see the color orange in spectrum. Because orange is the gravitational force of Mars.
But nobody conducting this test in other planet. They just taken the photos of visible light.
In mars planet, we would pass the visible light through one prism. Other end we should take the photos of vibgyor colors. By this method we can find what are the colors in mars planet?
I am sure, the color orange will not be in mars planet visible light spectrum. Instead of orange, the infrared could be next to the yellow color.
So we need to measure the vibgyor colors precisely.

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