Physics
Your weight on Mars is about 38% of your weight on Earth.
Mars has about 38% of Earth's surface gravity, so a 70 kg person would weigh about 26.6 kg-equivalent on Mars.
Weight is the force gravity exerts on your mass. Because Mars is smaller and less massive than Earth, its surface gravity is just 3.71 m/s² versus Earth's 9.807 m/s².
To find your Martian weight, multiply your Earth weight by the ratio of Martian to Earth gravity: 3.71 ÷ 9.807 ≈ 0.378.
Weight on body = Earth weight × (body gravity ÷ Earth gravity)70 kg on Earth × (3.71 ÷ 9.807) ≈ 26.5 kg-equivalent on Mars.
No. Your mass is the amount of matter in you and stays constant. Only your weight — the pull of gravity on that mass — changes.