Gravity is a fundamental interaction that governs how objects with mass attract one another. When discussing the gravity of a planet, scientists focus on surface gravity, which is the acceleration an object experiences at the planet’s surface. This value is measured in meters per second squared (m/s²) or often expressed in terms of Earth’s gravity, known as g’s, where Earth’s surface gravity is defined as 1 g. Surface gravity determines the weight of an object on that world and is a direct result of a planet’s specific physical properties.
The Planet with the Highest Surface Gravity
The planet with the highest surface gravity in our Solar System is Jupiter. If a person could stand deep within its atmosphere, they would experience an acceleration of approximately 24.79 m/s². This translates to about 2.5 times the gravitational pull felt on Earth. An object weighing 100 pounds on Earth would weigh over 250 pounds on Jupiter. Jupiter’s immense gravity is a direct consequence of its overwhelming mass, which is more than twice the mass of all the other planets in the Solar System combined.
Jupiter’s gravitational measurement is taken at the one-bar pressure level within its atmosphere, which scientists define as its effective “surface” since it lacks a solid ground. The planet’s enormous scale and composition of hydrogen and helium contribute to this powerful gravitational environment.
How Mass and Radius Determine Surface Gravity
Surface gravity is determined by a balance between a planet’s mass and its radius. According to Newton’s Law of Universal Gravitation, surface gravity is directly proportional to the planet’s mass but inversely proportional to the square of its radius. This inverse-square relationship means that a small increase in radius can cause a substantial decrease in surface gravity, even if the mass remains the same. The gravitational acceleration experienced is felt at a distance from the planet’s center of mass, and the larger the radius, the further away that “surface” point is.
This relationship explains why the immense gas giants do not have exponentially stronger surface gravity than Earth. While Jupiter has over 300 times Earth’s mass, its radius is more than 11 times larger. The squared radius in the denominator significantly dilutes the effect of the massive numerator, preventing the surface gravity from being hundreds of times Earth’s value. For instance, Saturn is less dense and more spread out than Jupiter, and its surface gravity is actually less than Earth’s at around 1.06 g.
Gravitational Extremes Across the Solar System
The gravitational environment on Earth serves as the standard, with a value of 1 g, or 9.8 m/s². The lowest surface gravity among the major planets belongs to Mars, with a value of approximately 3.71 m/s², or about 0.38 g. Mercury is a close second, with a surface gravity of about 3.7 m/s², also approximately 0.38 g.
Standing on a low-gravity world like Mars would be a profoundly different physical experience. Objects would weigh only about 38% of their Earth weight. A person could jump significantly higher and farther, and any physical activity would require far less effort due to the reduced downward pull.