Robert Mars was a Starfleet security guard serving in the late 24th century.
By 2381, Mars was assigned to the USS Enterprise-E. After the Enterprise and the USS Aventine traversed a subspace tunnel from the Azure Nebula ending up near the Carina Arm near the meridian of the Gamma and Delta Quadrants, they were attacked and boarded by a group of Hirogen. Mars was one of the ten security officers assigned to protect the Bridge and Captain Jean-Luc Picard, but the Captain refused to leave; second officer Miranda Kadohata ordered Mars, Austin Braddock, and Cruzen to surrender their TR-116 rifles and depart the Bridge. (ST - Destiny novel: Mere Mortals)