What is the gravity on Mars?

A planet's gravitational acceleration depends on its mass and radius. Mars has only a fraction of Earth's mass -the ratio is 0.107- and an equatorial radius of 3,396.2 kilometers versus Earth's 6,378.1 kilometers. At the equator, gravitational acceleration is 3.69 m/s², versus 9.78 m/s² on Earth (a ratio of 0.377); average values are 3.73 versus 9.82 m/s² (a ratio of 0.380). A person's mass stays unchanged there, but they weigh much less, which also changes the usual sense of force and balance.

For space exploration, reduced gravity is an advantage on departure and a problem on arrival. Escape velocity is 5.03 km/s, versus 11.19 km/s on Earth; that's why a rocket returning from Mars can be small. But landing lacks that braking help: surface atmospheric pressure is barely about 6.36 millibars, too little to slow a heavy vehicle with parachutes, yet too much to ignore the heat of entry. That's why every landing needs a heat shield, parachutes and engines.

Within the solar system, Mars sits between the Moon and Earth: on the Moon it's 1.62 m/s², on Mars an average of 3.73 m/s², and on Earth an average of 9.82 m/s². What effect an intermediate value like that, sustained for months, has on bones, muscles, circulation and eyes is unknown, because no one has ever lived that long under reduced gravity. The only certainty is that walking, lifting weight and falling behave differently: jumps go farther, falls are slower, and raised dust takes longer to settle.