... galaxy had had a carbon-hydrogen-oxygen base. Nobody'd yet found any silicon based life, although a good many organisms used the element. No one yet had found a planet with a halogen atmosphere, and, although there might be weird forms of life at the bottom of the soupy atmospheres of the methane-ammonia giants, no brave soul had ever gone down to see—at least, not on purpose, and no ... — Cum Grano Salis • Gordon Randall Garrett
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