The crossword solutions for the term 'Mercury, but not Mars' are CAR and METAL. Mercury is a planet in our Solar System, while Mars is another planet in our Solar System. CAR is an acronym for 'combustion-powered automobile', which is a type of vehicle powered by an internal combustion engine. METAL is a type of material that is made up of one or more elements such as iron, aluminum, copper, and zinc. It is often used to make cars, buildings, and other objects.