For some reason, I got thinking about the pairs of adjectives venereal and Venusian, martial and Martian, and jovial and Jovian. The second of each pair relates only to the Roman goddess or god or the planet, while the first relates to personality (jovial), soldiers or personality (martial) and love (venereal). The last could have positive collocations (affections, delights) but has come to be associated primarily with sexually transmitted diseases and their symptoms.
So, are there also mercurial and Mercurian, and saturnial and Saturnian? No, lower-case mercurial refers to personality and upper-case Mercurial to the god and the planet. Lower-case saturnian refers to personality ‘prosperous, happy, or peaceful’ and upper-case Saturnian to the god and the planet. But saturnine means ‘sluggish in temperament; gloomy; taciturn’ (somehow one god and/or planet was seen to be responsible for both happiness and gloom) as well as ‘due to absorption of lead … suffering from lead poisoning’ . (In Gustav Holst’s The Planets, Saturn is subtitled ‘The Bringer of Old Age’.)
These were the planets known to the ancients and early and middle English speakers. From the modern age come Uranian, ‘pertaining to the planet Uranus’ and ‘(of males) homosexual …from Aphrodite Urania heavenly Aphrodite, inspiration for male homosexuality in Plato’s Symposium’; Neptunian, relating to the god or the sea, the planet, or ‘(often lowercase) Geology. formed by the action of water’.
Where’s Pluto? For the sake of completeness, I’ll add Plutonian ‘Also, Plutonic of, relating to, or resembling Pluto or the lower world; infernal’.
Note also the chemical elements mercury (ancient), uranium, neptunium and plutonium (modern). In classical alchemy, Venus was associated with copper (?a woman’s mirror), Mars with iron (?a soldier’s weapons), Jupiter with tin (??) and Saturn with lead (see ‘lead poisoning’ above).
[all definitions from Dictionary.com]