JF Ptak Science Books Post Expanding a Lost Earlier Post (#67)
Where did the smile of the Sun go? Anthropomorphic images of the Sun
have appeared in books in the West for several hundred years, and in
almost every case where the Sun has a face, it is usually
expressionless, its mouth drawn into a mid-Western farmer/Abe Lincoln
horizontal, a tightly drawn nothing. Two thin lips, firmly repulsing
all emotion. The face of the Sun was insurmountable, a tabula rasa, showing perhaps that there was nothing there at all inhabiting this
iconographic image of The Creator to give the poor observer a glimpse
into the depths of the future.
This observation seems to stand for Sun Gods and Goddesses as well, even the ones who are being tugged or pulled or charioted across the vaults of the heavens—the Nordic Sól, Greek Helios , Roman Sol Invictus, Vedic Surya and of course Elijah ascending to Heaven in a Chariot of Fire, all seem pretty intractable. But in general images that we see of Sun deities like Apollo, Greece and Rome; Freyr, Norse; Garuda, Hindu; Huitzilopochtli (Uitzilopochtli), Aztec; Inti, Inca; Liza,West African; Lugh, Celtic and Re (Ra) and Isis, and on and on, show a small, set pair of lips, if they have a mouth at all, and this going back beyond the Sumerians (Shamash).
When the Sun really loses its human personae in the 17th century (the scientific sun and stars beginning much earlier, as in for example Allessandro Piccolomini’s Della Sfera del Mondo, 1552, with simple star maps unadorned by icons and written in the vernacular), it is replaced with starry images which seem to somehow have more emotional authority than the sun images with faces. Perhaps the sun was meant to have this Delphic, blank-mirroring quality, given its importance as a giver (and taker) of things,
and that it was not within human capacity to understand it as an emotive entity, especially during bad times. But in those times of Good and Bad it wasn’t necessary to see a frown or a smile on an image of the Sun, I guess because of the complaints of redundancy.
No matter, though, as the modern astronomical text took care of the Sun and its missing buckets of smiles in due course—until more modern times, when the Sun is made to have a matching disposition, a result of kinder modern artists. 
Now the Moon, well, that’s another matter…