Mars (and the Greek counterpart Ares) were frequently depicted on Roman and Greek coins. In Roman mythology Mars was the god of war and protector of the Roman army. In mythology he was the father of Romulus and Remus.
Above is a bronze sestertius of Marcus Aurelius with the reverse showing Mars.
Here is an article from NGC ancients about coins with the image of Mars (or Ares).
https://www.ngccoin.com/news/article/12676/ngc-ancients-mars-ares/