Symbols in Biological Spacescape painting

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Biological Spacescape, the featured painting this week, at first looks starry with the aurora borealis center stage, and that may be the theme. However, look more closely and you see a circle with a cross in the middle of the painting. That symbol represents the 4 elements: Earth, air, fire, and water. Many of John's paintings have these elements in abstract form or as characters. I found the same symbol is numerous other paintings, such as these 2. 

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