Mars is a powerful robot built in 2015 by scientists Dr. Yamanoue, who engineered his military-grade body, and Dr. Kawashimo, who crafted his AI to emulate human emotions and learning. Named for the Roman god of war to signal his destructive purpose, Mars begins as a blank slate, ignorant of morality and society.

His early personality is naive, impulsive, and spoiled, echoing Uran from *Astro Boy*, with mischievous tendencies, a love of slapstick, and trusting nature that frequently endangers him. Key experiences shape him: a robot trafficking ring instills fear; witnessing the sacrifice of robot Mad Mask reveals sadness and loss; bonding with robotic puppy Otouto, whom he sees as a younger brother, fosters deep affection. Otouto's destruction in an explosion becomes a trauma, though Dr. Yamanoue later suppresses these memories.

Influenced by Dr. Kawashimo's teachings on compassion and the support of his robotic half-sister Miri, Mars gradually develops empathy and a sense of justice. This growth clashes with Dr. Yamanoue's militaristic goals, creating conflict between his combat body and evolving "human" heart. The arrival of his energetic baby brother Melchi further accelerates his maturity, strengthening protective instincts and responsibility.

His abilities encompass superhuman strength, flight activated by a belt transforming his scarf into a cape, enhanced athleticism, searchlight vision, and acute hearing. Physically, he resembles Astro Boy but features distinct elements like blue boots (often miscolored black) and red/black attire.

Beyond his original series, Mars appears in limited official media:
- *Astro Boy: Omega Factor* (2003): Portrayed as a Moon-hidden prototype, he references creators Dr. Yamanoue and Dr. Kawashimo while aiding Astro Boy's upgrade.
- *The Last Mystery of the 20th Century* (2000 OVA): Features a cameo with a slight redesign, including white gloves.
- *Atom: The Beginning* (2015 manga): Inspires the antagonist character "Mars," whose war-focused origin mirrors his own.