Author Topic: Lunar Regolith Color Differences  (Read 720 times)

Offline BDL

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Lunar Regolith Color Differences
« on: December 23, 2018, 04:19:46 PM »
So I bought the book Apollo to The Moon which is by National Geographic and Smithsonian Institute of Air and Space and on the cover of the book a panorama taken by Charlie Duke of Descartes Highland. In it is John Young next to the Lunar Rover and the Lunar Module.
But what caught my eye was the unusually bright color of the regolith around it. The ground is noticeably brighter in color than photos, for example, of Buzz Aldrin in Tranquility Base.

Here’s the specific Apollo 16 panorama I’m referring to:
https://www.lpi.usra.edu/resources/apollopanoramas/pans/?pan=JSC2007e045380&zoom=True

Here’s the Apollo 11 photo I’m referring to: https://www.google.com/search?q=Buzz+Aldrin&client=safari&hl=en-ki&prmd=niv&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiBwbaK8LbfAhVLHDQIHU7-B4sQ_AUoAnoECA4QAg&biw=414&bih=617#imgrc=OrCtFTAR4v9ESM&imgdii=bLvkDKbPq2WEHM

Is the difference brightness due simple to different locations? Or was it the result of cameras?
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Offline bknight

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Re: Lunar Regolith Color Differences
« Reply #1 on: December 23, 2018, 05:49:24 PM »
I'm definitely not a camera guy, but would it happen to be the way the camera is facing the sun?  If you look at the foreground the regolith looks very much like the panorama, at least to me. 
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Offline BDL

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Re: Lunar Regolith Color Differences
« Reply #2 on: December 23, 2018, 07:40:08 PM »
I'm definitely not a camera guy, but would it happen to be the way the camera is facing the sun?  If you look at the foreground the regolith looks very much like the panorama, at least to me.
Makes sense. Presuming the Apollo 16 mission took place at a different time on the lunar day, it’s possible that the sun had lit the regolith in just the way that would make it seem so bright.
“One small step for [a] man, one giant leap for mankind.” - Neil Armstrong, 1969

Offline onebigmonkey

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Re: Lunar Regolith Color Differences
« Reply #3 on: December 24, 2018, 03:08:26 AM »
The Apollo 16 pan was done during the 3rd EVA, so conditions were definitely a lot brighter than for Apollo 11.

Offline Kiwi

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Re: Lunar Regolith Color Differences
« Reply #4 on: December 24, 2018, 08:51:48 AM »
Is the difference brightness due simple to different locations? Or was it the result of cameras?

In cases like this there are often multiple factors at work in earthbound photos:  Camera, film, filter or glass in front of lens, exposure, location, angle of the sun to the ground, angle of camera to the sun, and photographer. Then there are processing factors - how the person making the finished photograph wanted it to look and the methods and materials used

By using a program called HTMLcolor to analyse the panorama, I found that whoever processed it must have deliberately made the greys as neutral as possible, because to my surprise, many of them were of exactly the same number in all three RBG values (red, blue, green).

But all the same, it was roughly over three times brighter in the down-sun portion (219, 219, 219) at the ends, than in a fairly bare part of the ground in the up-sun view (185, 185, 184) below the rover's right-hand wheel. If you didn't notice that difference, check again. It's easy for our brain to kid us that it's the same brightness everywhere in the panorama.

The astronauts generally used three different apertures for shooting panoramas. The smallest for down-sun, largest for up-sun (four times the exposure as down-sun), and in-between for the two right angles to the sun (twice down-sun).

Google lunar "lunar regolith colour/color" because right from Apollo 8 onward there were many discussions of the subject and later much controversy from hoaxland because many of the critics have never analysed their own photos or deliberately photographed a plot of ground or a piece of neutral grey carpet with a great variety of all the factors listed above.

Also look at many more photos of the moon. For instance, in the few very distant photos of the LM we can see the effect that the descent engine had in lightening the ground nearby by blowing away the topmost layer of soil. Keep in mind that in an up-sun view you are seeing a lot of shadow and in a down-sun view a lot less. That can give an illusion of darker soil when it's actually just much more shadow. It's also why we often see a "halo" around the shadow of the astronaut's chest in panoramas - almost no ground shadows at all.
« Last Edit: December 24, 2018, 08:57:48 AM by Kiwi »
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Offline ka9q

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Re: Lunar Regolith Color Differences
« Reply #5 on: January 01, 2019, 08:27:45 AM »
Apollo 16 landed in the lunar highlands, while most of the other missions (including 11) landed in the mare. Maybe that contributed to the brighter surface, though I suspect it had more to do with sun and view angles.

Offline Dalhousie

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Re: Lunar Regolith Color Differences
« Reply #6 on: January 02, 2019, 01:59:03 AM »
Apollo 16 landed in the lunar highlands, while most of the other missions (including 11) landed in the mare. Maybe that contributed to the brighter surface, though I suspect it had more to do with sun and view angles.

According to the lunar sourcebook maria albedo is 7-10% whereas that of the highlands is 11-18%