## surface gravityThe local gravitational field strength at the surface of an astronomical body. It determines, for example, how much a person would weigh if they were to stand on that object. In the case of a gas giant or a star, the surface gravity is calculated as if there were a solid surface at the top of the atmosphere. Local gravitational field strength is given by g, the force acting
on a mass of 1 kg at the surface, according to the formula g = GM/r^{
2}, where M is the mass of the body, r its radius, and
G the gravitational constant (= 6.67 × 10^{-11} Nm^{2}).
Thus greater mass means greater surface gravity, but greater diameter means
lesser surface gravity. For the Earth, g has a value of about 9.8
newtons/kg. For Mars, by contrast, g
is only about 3.7 N/kg, or 0.38 times as much. g is also known as
the acceleration due to gravity. The table
below compares the surface gravity of various bodies to that of the Earth.
The surface gravity of a world is expected to strongly influence what, if any forms of life, may appear on it. For more on this, see alternative forms of life. ## Related entry• gravity## Related category• ASTRONOMICAL QUANTITIES | |||||||||||||||||||||||||||||||||||||

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