Google is your friend. The first choice will send you paper ones for free. The nicer ones have a minimum order of 2 @ $7.00 apiece, which isn’t bad. http://www.rainbowsymphony.com/freestuff.html

“This would be the same calibration that turned the Stars and Stripes on Viking purple and orange?”

It was when a technician noticed the off-coloring of the flag that everyone realised that correction was necessary. I remember that very vividly.

But let’s say, hypothetically, that in some inexplicable way, calibrating to the flag throws the color-balance way off for images of the calibration stripe. Similarly, adjusting to the stripe throws the flag’s colors way off. Which one do you go with? You can’t go with both, since they’re inconsistent with each other. It can at least be said that the calibration stripe was designed explicitly for the purpose of color-correcting images. The pigments in the flag were probably chosen on a much more casual basis than those in the calibration stripe. I’d rather go with the stripe than the flag.

“The sky should be blue on Mars for the same reason that the sky is blue on Earth – Rayleigh scattering of the same light source. The chemical composition of the sky should not matter unless there is a gas with an intrinsic color present.”

Rayleigh scattering is dependent upon several variables. Sunlight isn’t the sole player. Similarly, Rayleigh scattering per se isn’t the sole mode by which light is scattered. Rayleigh scattering is dominant for wavelengths at least an order of magnitude larger than the particles in the scattering medium. For particles larger than that, the dominant mechanism is Mie scattering. On top of that, there’s a mode called Raman scattering.

More:
What Color is Mars?
http://www.badastronomy.com/bad/misc/hoagland/mars_colors.html

What Color is the Martian Sky?
http://webexhibits.org/causesofcolor/14C.html

This would be the same calibration that turned the Stars and Stripes on Viking purple and orange?

“But even if you didn’t know this, why would you expect the sky to be the same color as on Earth? Mars’ atmosphere has been known for decades to have a lower pressure, and different abundances of gases.”

The sky should be blue on Mars for the same reason that the sky is blue on Earth – Rayleigh scattering of the same light source. The chemical composition of the sky should not matter unless there is a gas with an intrinsic color present.

Shawn S. Says:
I’m an atheist and photos like these and my studies of microorganisms give me that great feeling that some people describe as spiritual. I love feeling that wonder and awe at the universe that photos like these evoke. It makes me happy to exist. Thanks for the post, Phil.

I feel the same way, though I don’t know that it’s because I’m an atheist. I look at these photos and see landscapes and rocks that look familiar to our own world yet are millions of miles away. It just drives home to me how connected everything in the universe is – and we made something that’s cruising around on another planet! (Perhaps that solidifies my worldview, after all.)

I love looking at the “Slide Show: Road Trip” pictures on the NASA page (middle right sidebar). Close-ups of rocks, how awesome. Somebody said to me, “Why are we studying rocks on another planet…we could spend the money…” blah, blah. I replied that we’re trying to figure out where the rocks in his head came from. Really, I can’t understand how people fail to feel excited looking at these photos – doesn’t it at least fuel their imagination?

Side note: I can’t wait to see the results of the STEREO mission. Looking at solar storms in 3-D…woo-hoo! I gotta get me some glasses. (-8~

Links:
http://www.nasa.gov/mission_pages/mer
http://www.nasa.gov/mission_pages/stereo/main/index.html