Originally posted by doesntmakesense
This is a bit off-topic, but this has me wondering: Is the galaxy gray? And on those lines, why is earth so colorful?!
I'm not sure if you are asking : "why are the pictures from Mars often black and white?"
If that's what you are asking, then it's because of the way many digital cameras work...
Digital cameras with CCD light sensors are essentially color-blind. The CCDs of "consumer cameras" and the CCDs of NASA's space probes cannot see
light in color -- they only see it in greyscale.
To get color, your home consumer camera and NASA's probes view each subject through various filter which give them grayscale versions of the same
image but with different grayscale intensities depending the filter. By combining and analyzing the different grayscales, a computer can figure out
what the actual colors are.
In your home camera, the filter used is called a Bayer filter, and it creates one image based on simultaneously stacking three images seen through a
single red-green-blue filter . The computer in your camera analyzes each grayscale pixel seen through a red, green, or blue filter, and then
constructions the one color image that you see out of these combined filtered grayscale images.
This all happens inside
your camera for most peoples home consumer cameras.
Many NASA probes use this same basic concept, but instead of the different grayscles being analyzed inside the spaceprobe and having the space probe
construct a color image from these, the various grayscales are transmitted to Earth to be combined by computers here.
That's why many of the Raw images coming from NASA probes are grayscale.
However, not all NASA probes do this. Curiousity's MastCam and its MAHLI Camera utilize Bayer filters (like your home digital camera) and the
computer onboard Curiosity is what tries to determine color from the Bayer-filtered grayscale images.
And keeping that in mind, and looking a the OP's image specifically, NASA constructed this image by emphasizing the tracks as seen through the Red
filter. This helped the tracks to stand out against the rest of the image (and when I say "through the Red Filter", I mean the grayscale that is
created when seen throug a red filter. The Mars Reconaissance orbiter HIRISE camera has a Red filter, a Blue-Green filter, and a near-Infrared
Here is a description as to how the OP's image was processed:
This image was acquired for color coverage of the region that the Curiosity rover may explore, but we acquired some extra RED (monochromatic)
coverage of the rover tracks.
edit on 1/17/2013 by Soylent Green Is People because: (no reason given)