The term 'MARS' THING' is a crossword solution that can be filled in with the three-letter word 'WAR'. Mars is the Roman god of WAR, and the term 'MARS' THING' is a reference to this. WAR is an armed conflict between two or more countries, or between two or more groups within a country. It is characterized by physical violence, destruction, and death. WAR has been a part of human history since ancient times, and continues to be a major source of conflict in the modern world.