Gravity is the attractive force that exists between any two objects with mass. Since Mars is a planet with significant mass, it possesses its own gravitational field, which anchors its atmosphere, two moons, and everything on its surface. This force operates identically on Mars as it does on Earth, but the strength of the pull is noticeably different due to the planet’s smaller size. Understanding this difference is crucial for designing future missions and anticipating the experience of astronauts on the Martian surface.
How Much Gravity Does Mars Have
The surface gravity of Mars is significantly lower than that of Earth, measuring approximately 38% of our planet’s gravitational acceleration. This is often expressed as 0.38 g, where one “g” is the standard gravity of Earth. This ratio dictates the perceived weight of an object or person standing on the ground.
This means a person’s weight is reduced by nearly two-thirds when traveling from Earth to Mars. For example, an individual who weighs 150 pounds on Earth would only register about 57 pounds on the Martian surface. The average gravitational acceleration on Mars is 3.728 meters per second squared, compared to Earth’s 9.8 meters per second squared.
What Physical Attributes Create Martian Gravity
The difference in surface gravity between Mars and Earth is a direct result of the two planets’ differing physical properties, namely their total mass and radius. The gravitational force a planet exerts is directly proportional to its mass but inversely proportional to the square of its radius. Mars has only about 11% of Earth’s total mass.
The planet’s diameter is smaller, measuring about half that of Earth, which results in a mean radius that is approximately 53% of Earth’s. When calculating surface gravity, the smaller mass significantly decreases the gravitational pull. However, because the surface is closer to the planet’s center of mass, the smaller radius partially offsets the effect of the lower mass, leading to the final value of 0.38 g.
The Experience of Low Gravity
For a human astronaut, the feeling of 0.38 g would be noticeably lighter, allowing for a form of locomotion somewhere between walking and floating. Movement would not be the exaggerated, slow-motion bounding seen on the Moon’s 0.16 g gravity, but instead a more graceful, loping gait. An astronaut could jump approximately three times higher and stay airborne for a longer duration than they could on Earth.
This reduced weight allows astronauts to carry much heavier loads of equipment, tools, and rock samples than they could manage on Earth. However, the lower gravity presents long-term physiological challenges, as the human body is adapted to Earth’s one g environment.
Studies suggest that partial gravity below 0.4 g may be insufficient to maintain musculoskeletal and cardiopulmonary health over long periods, risking bone density loss and muscle atrophy. To mitigate this, future Martian habitats may need to incorporate artificial gravity systems, such as centrifuges, to provide a higher gravitational load for the crew.
Gravity’s Impact on Mars’s Atmosphere
Mars’s relatively low gravity played a significant role in the loss of its early, thicker atmosphere over billions of years. Gravity is the force that binds atmospheric gases to a planet, and the weaker Martian pull means gas molecules can more easily achieve the escape velocity needed to drift into space. This process, known as atmospheric escape, is particularly effective with lighter gases like hydrogen and water vapor.
The weaker gravitational field is compounded by the lack of a globally generated magnetic field, which on Earth shields the atmosphere from the erosive solar wind. The combination of low gravity and solar wind stripping has resulted in a planet with an atmospheric pressure less than one percent of Earth’s.
While Mars’s gravity is strong enough to hold onto its current tenuous atmosphere, which is mostly carbon dioxide, the lower gravity also contributes to a higher atmospheric scale height. This means the atmosphere extends farther from the surface than Earth’s does.