mars has 1 distinct synonym spread across 1 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a small reddish planet that is the 4th from the sun and is periodically visible to the naked eye; minerals rich in iron cover its surface and are responsible for its characteristic color
“Mars has two satellites”
(Roman mythology) Roman god of war and agriculture; father of Romulus and Remus; counterpart of Greek Ares
Synonyms, antonyms and the broader and narrower relations for mars come from Princeton University’s WordNet. Full sources and licences.