high resolution textures for galileian moons

LICENSE.md

@@ -14,10 +14,10 @@
         - Downscaled by 2x with LoHalo interpolation
         - Adjusted contrast with GIMP's "Colors"→"Curves", by pulling x=128/y=128 down to y=96.
         - Exported as 80% quality JPEG
-    - Io: By NASA, public domain
-    - Europa: By NASA, public domain
-    - Ganymede: By NASA, public domain
-    - Callisto: By NASA, public domain
+    - Io: [By Björn Jónsson, free to use, with attribution](https://bjj.mmedia.is/data/io/io.html)
+    - Europa: [By Björn Jónsson, free to use, with attribution](https://www.planetary.org/articles/0218-mapping-europa)
+    - Ganymede: [By Björn Jónsson, free to use, with attribution](https://bjj.mmedia.is/data/ganymede/index.html)
+    - Callisto: [By Björn Jónsson, free to use, with attribution](https://bjj.mmedia.is/data/callisto/index.html)
     - Saturn: [By Solar System Scope, CC BY 4.0](https://www.solarsystemscope.com/textures/)
     - Uranus: [By Askaniy, CC BY-SA 3.0](https://www.deviantart.com/askaniy/art/Uranus-Texture-Map-763551816)
     - Neptune: [By Solar System Scope, CC BY 4.0](https://www.solarsystemscope.com/textures/)