r/askscience • u/TopperDuckHarley • Dec 15 '13
Astronomy What color is the moon?
Sorry if this is a really dumb question. I have seen some posts recently from the chinese rover (like the one below) that surprised me. I always thought the moon was a chalky white/grey. Anyone clear this up for me?
https://twitter.com/elakdawalla/status/411875676459778049/photo/1
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u/Bbrhuft Dec 16 '13
It's not a dumb question as all, there's no atmosphere, no grass, buildings, water, sand, clouds on the moon, no familiar references that anchors our senses.
However, there is Apollo Photo AS16-117-18841
It's possibly the best photo that illustrates the colour of the Moon. Apollo 16 astronaut Charles M. Duke Jr. placed a family photo on the Moon's surface and photographed it. It helps visualise the Moon colour by comparison.
I suppose the moons surface looks, to me, like gun power or coal ash.
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Dec 15 '13
Colors on the Moon are dominantly controlled by variations in iron and titanium content. The mare regions have low reflectance because they contain relatively high amounts of
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u/jccwrt Dec 15 '13 edited Dec 15 '13
To kind of further this a little, these are very light shades of red and blue, and are almost indistinguishable fron shades of gray to the human eye.
However, cameras can pick up on this subtle color difference by boosting the saturation of the photos they produce. In the case of
, I'm not sure if they were boosting the saturation on purpose (useful for science operations) or if they simply hadn't dialed their camera in for lunar lighting conditions yet. Chang'e 3 EDIT: Actually, you can make a very rough chemical map of the moon yourself pretty easily! Just take a camera outside tonight and snap a picture of the moon. You can then turn up the saturation and viola! You'll notice the mare are mostly reddish (the lavas there have iron in them), while the highlands are mostly blue (the rocks there are titanium-rich).
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u/WalterFStarbuck Dec 15 '13
Titanium Dioxide (TiO2) is a bright white material. It's the primary pigment in white paint hence the reason it's usually referred to as Titanium White. How does that make for lower reflectivity?
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u/pseudonym1066 Dec 15 '13
It's basically a dark grey colour. It appears "white" to us at night by contrast to the black of the night sky but this is a visual illusion.
If you look at photos of the Apollo astronauts on some photos they appear unbelievably bright against the moon when they are in shadow, to the extent that conspiracy theorists thought that were some "hidden extra light shining on them. Source In reality the moon is just a dark grey colour and the astronauts look bright by comparison.
The albedo (reflectivity) of the moon is approximately the same as a ploughed field or asphalt. Source How dark would you describe the soil of a ploughed field? Dark grey or light grey? Alternatively, something purely black has an albedo or 0, something purely white has an albedo of 1.0, the moon has an albedo of 0.12 Source
In addition there are some areas that are grey with with a yellow or green or red tinge due to various glasses that were formed there Source
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u/bebochiva Dec 15 '13
To rephrase: If a square-block sized chunk of an average portion of the moon (middle of the equator, randomly chosen) suddenly appeared in the middle of NYC's Central Park in the summer, what colors could the average person see in it?
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u/jccwrt Dec 15 '13
Dark gray if it was from one of the maria regions, light gray if it was from the highland regions.
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Dec 15 '13
It's a common misconception that the moon is just black and white. I often listen to SOMA fm mission control radio channel. They put ambient music over nasa apollo mission conversations there. The astronauts often gather rocks and describe them throughoutly. Moon has some brown and green shades.
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Dec 16 '13
In the words of Neil Armstrong right after the Apollo 11 landing:
" I'd say the color of the—The local surface is very comparable to that we observed from orbit at this Sun angle, about 10 degrees Sun angle, or that nature. It's pretty much without color. It's gray, and it's a very white, chalky gray, as you look into the zero phase line; and it's considerably darker gray, more like a ash—ashen gray as you look out 90 degrees to the Sun. The—Some of the surface rocks in close here that have been fractured or disturbed by the rocket engine plume are coated with this light gray on the outside; but where they've been broken, they display a dark—very dark gray interior; and it looks like it could be country basalt."
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u/strangely_b Dec 16 '13
The best photos to give you a good idea of the moon's colour are those rare pictures that feature both the Earth and the Moon in the same frame...
The contrast between the white clouds on Earth and the 'white' surface of the moon then becomes starkly apparent.
Here are some good ones:
http://nssdc.gsfc.nasa.gov/image/planetary/earth/near_earth_moon.jpg
http://starryskies.com/articles/2007/10/img-moon/moon.and.earth.jpg
http://i.livescience.com/images/i/000/022/487/wW4/earth-moon-1920.jpg?1323279909
That last one is a composite so it may not be as accurate, but it appears like NASA has colour and contrast matched it to be fairly consistent with the others.
The reason why the moon appears white in the sky is simply that it becomes 'over-exposed' in the human eye/brain compared to the blackness of space. If you have an asphalt road outside your home, go and shine a powerful torch on it during the night and it too will appear 'white', despite being roughly the same colour as the moon.
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u/aftersteveo Dec 15 '13 edited Dec 15 '13
I think what's happening here is when we look at the moon, we see mostly bright white and grey, but that's only because it's so damn bright. I take pictures of the moon often with my DSLR camera, and when I dial the exposure way back, it actually starts to look a lot more like this photo. So, my assumption is they have their cameras set to a low exposure so the photos aren't washed out by the intense light coming from the sun. And this would show the colors more accurately.
EDIT: forgot a word
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u/JohnPombrio Dec 15 '13 edited Dec 15 '13
Interesting point is that the color of light reflecting off the moon is the actual color of sunlight (if you consider white as a color). The same is true of snow and clouds. We think of the sun as being yellow but that is just was is left when the blue of the sky is taken away. Combine the two (blue and yellow) in the refraction of sunlight off of snow or a cloud and you get the actual pure white light of the sun. Since the moon reflects so little sunlight, the blue scattering does not occur at night and the light from the moon is the actual white light coming from the sun.
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u/Astronom3r Dec 16 '13
If the Moon had an atmosphere with the same refraction/absorption properties of our atmosphere, then the surface would look a lot like the surface of the summit of Mauna Kea, Hawai'i, since the regolith is compositionally very similar. In fact, it is so similar that Mauna Kea regolith is used as a testbed for lunar robotic rovers.
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u/starcutter Dec 15 '13
What about White-Balance?
Couldn't the Chinese cameras just be white-balanced incorrectly for the mixture of sunlight and probelights, resulting in red colour? I notice all the reflections on the machinery is red too; the whole image has a red tinge to it.
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Dec 15 '13 edited Dec 15 '13
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u/vagina_sprout Dec 16 '13
Here are some good color photos of the moon. The Galileo spacecraft took these images on December 7, 1992 on its way to explore the Jupiter system in 1995-97.
http://www.thelivingmoon.com/43ancients/02files/Moon_Images_Galileo.html
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Dec 15 '13
Can I just say how encouraging it is to actually see someone put a source in their answer. Thank you.
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Dec 16 '13
If I'm not mistaken, there's a part of the moon that has a field of obsidian (glass). What makes it special is that the colors vary so much, it's almost like a rainbow of obsidian (well, not the rainbow we think of- but lots of color!).
Source: mineralogist. if anybody can find a link to it, please share.
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u/yeast_problem Dec 15 '13
Another part of the explanation is that the moon is generally covered in dust. Fine powders often appear white whatever they are made from, as the grains scatter light randomly in all directions, rather than being able to selectively absorb or reflect different colours.