# Mars' Sky (and Richard Hoagland!)
**URL:** https://boards.straightdope.com/t/mars-sky-and-richard-hoagland/143312
**Category:** Factual Questions
**Created:** [December 17, 2002, 12:23pm UTC](https://boards.straightdope.com/t/mars-sky-and-richard-hoagland/143312 "2002-12-17T12:23:41Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Erroneous](https://boards.straightdope.com/u/Erroneous)
#### Post date: [December 17, 2002, 12:23pm UTC](https://boards.straightdope.com/t/mars-sky-and-richard-hoagland/143312/1 "2002-12-17T12:23:41Z")
Hopefully the Hoagland reference in the title will attract best of the SDMB’s debunkers. For those who don’t know, Richard Hoagland is the original ‘face on Mars’ guy, and is, of course, quite nutty. I read his stuff for fun, and because the articles on his webpage occasionally contain links to pretty pictures of Mars.
Anyway, his [latest offering](http://www.lunaranomalies.com/colors.htm) concerns the colour of Mars’ sky. It’s also a typically bloated anti-NASA rant, so to summarise it for those who can’t be bothered reading it (and I don’t blame you):
The first images to come back from the surface of Mars originally showed a pale blue sky and Earthy-brown ground, but were soon after altered to show a pink sky and much redder ground. This much is historical fact. However, whereas NASA claims this alteration was undertaken due to the original image being the result of human error (i.e. wishful thinking, to see Mars as more Earth-like), Hoagland (purveyor of THE SHOCKING TRUTH that he is) posits that it is, naturally, all a vast conspiracy. The original image was in fact the more accurate one, but the shadowy puppetmasters at NASA tweaked the colours to make Mars look barren and lifeless. Why? Because of some alleged, obscure 1950’s document, the ‘Brookings Report’, forecasted the collapse of civilisation if the discovery of ANY life beyond Earth was announced, or apparently even suggested.
Phew.
Now, to my question, which isn’t really related to Hoagland’s conspiracy, but was inspired by that article: what would the true colour of Mars’ sky be, to a human observer on the surface of that planet? Why do some pictures of Mars (see Hoagland’s article for examples) seem to show a bluish atmospheric haze around the planet, while some show this haze to be red or pink? Is it that the ‘true’ colour of the Martian atmosphere is blue, but all the dust blowing around makes it usually appear pink? I’m confused, and Hoagland was no help. Although he did make me giggle. At him.
Thanks.
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### Author:  [@PigBoy](https://boards.straightdope.com/u/PigBoy)
#### Post date: [December 17, 2002, 12:45pm UTC](https://boards.straightdope.com/t/mars-sky-and-richard-hoagland/143312/2 "2002-12-17T12:45:22Z")
> [@](#):
>
> \*Originally posted by Erroneous \*
> \*\* Is it that the ‘true’ colour of the Martian atmosphere is blue, but all the dust blowing around makes it usually appear pink?
> \*\*
I have a textbook that says this is the case:
> [@](#):
>
> Airborne dust also affects the color of the Martian sky, which is pink when dusty but blue when the air is nearly clear.
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### Author:  [@scr4](https://boards.straightdope.com/u/scr4)
#### Post date: [December 17, 2002, 12:52pm UTC](https://boards.straightdope.com/t/mars-sky-and-richard-hoagland/143312/3 "2002-12-17T12:52:09Z")
Check out the [weather, climate and life on Mars FAQ](http://humbabe.arc.nasa.gov/mgcm/faq/faq.html), in particular the 5th section.
As far as I know, [images from the Mars Pathfinder](http://nssdc.gsfc.nasa.gov/planetary/marspath_images.html) are “true color” and approximate the way the scene would look like to us if we were there.
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### Author:  [@BMalion](https://boards.straightdope.com/u/BMalion)
#### Post date: [December 17, 2002, 1:45pm UTC](https://boards.straightdope.com/t/mars-sky-and-richard-hoagland/143312/4 "2002-12-17T13:45:57Z")
How come I don’t see any thoats?
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### Author:  [@Mars\_Horizon](https://boards.straightdope.com/u/Mars_Horizon)
#### Post date: [December 17, 2002, 3:15pm UTC](https://boards.straightdope.com/t/mars-sky-and-richard-hoagland/143312/5 "2002-12-17T15:15:14Z")
Although it appears to be timing out right now, Phil Plait’s **Bad Astronomer** [website](http://www.badastronomy.com/bad/movies/redplanet2.html) indicates that Mars’ atmosphere appears “butterscotch” from the surface.
Mars the poster, as opposed to Mars the planet
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### Author:  [@BMalion](https://boards.straightdope.com/u/BMalion)
#### Post date: [December 17, 2002, 6:30pm UTC](https://boards.straightdope.com/t/mars-sky-and-richard-hoagland/143312/6 "2002-12-17T18:30:18Z")
> [@](#):
>
> \*Originally posted by Mars Horizon \*
> \*\*Mars the poster, as opposed to Mars the planet \*\*
As opposed to Mars the candy bar?
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### Author:  [@ForgottenLore](https://boards.straightdope.com/u/ForgottenLore)
#### Post date: [December 17, 2002, 8:44pm UTC](https://boards.straightdope.com/t/mars-sky-and-richard-hoagland/143312/7 "2002-12-17T20:44:06Z")
The blue sky on Earth is the result of scattering of sunlight due to nitrogen (_not_ oxygen or carbon dioxide) in the atmosphere. The only thing that a blue sky on Mars would prove was that there was a lot of nitrogen there. Big deal. Ya can’t breathe it, so why he thinks that indicates Martian life escapes me (unless it is primarily a biological by-product. Anyone?)
AFAIK there is no appreciable amount of nitrogen present in the Martian atmosphere, so it shouldn’t be blue.
As far as the original photos of Mars showing a blue sky, the explanation I heard was that the people calibrating the cameras adjusted the images until the sky “looked right”. This rings true to me. I worked in a photo lab many years ago, and the process of correcting color in pictures gets to be second nature after a while. You see an outdoor scene, you correct the color balance until the sky is blue. It’s automatic.