These are actually two slightly different effects. The retroreflected light around the shadow of a plane is the Glory. When you see it around the shadow of your head against mist below it’s the Spectre of the Brocken. The “aura” is rainbow-like, with separated colors, and is due to diffraction between different retroreflected rays.
The effect of bright light on dew-soaked grass is called Heiligenschein, and is due to dew-drops supported on hairs on the grass leaves. It’s basically the same effect as those retroreflectors discussed above that use glass beads. What happens is that the drop, like the glass bead, acts to focus the light onto the grass behind it. It’s not a perfect focus, but that’s not important. The light treflecting from the grass is sent back practically along a collimated beam the way it came, surrounding the shadow of your head with a bright patch. There’s no diffraction and no color separation, and even colored backgrounds (like green grass) give very white reflections.
You can look up these terms on the Internet, or see M. Minnaert’s classic text The Nature of Light and Color in the Open Air, or R.A.R. Tricker’s Introduction to Meteorological Optics, or Greenl;er’s book Rainbows, Haloes, and Glories
Neither of the effects scr4 is talking about is a glory/Brockenspekter (which are basically the same thing). What he’s talking about is seeing man-made retroreflectors (street signs and the like) from an airplane, a purely reflective effect. No diffraction or refraction involved.
Aaak – you’re right. I scanned too quickly and thought he was talking about the Glory (which is a diffractive effect), which I’ve seen many times around the shadow of my plane. I’ve never noted the retroreflector effect he speaks of.
If you just want to make a picture on the moon, I think it would be a less challenging engineering task (than building and operating mult-gajizawatt lasers) to just make a shadow puppet the size of, say, India and use that to cast a shadow picture on the face of the full moon.
It would be easier to launch a cluster of unmanned lunar landers, each equipped with a powerful laser. The landers land in a pattern that makes up the desired shape. All landers would then aim their lasers at the same spot on the earth. The pattern would only be visible from one part of the earth, but energy requirement would be very manageable. Even Apollo-size landers may be enough to do the job.