# surface gravity

Surface gravity is the 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 kilogram 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} newton. meter squares, 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 per kilogram (N/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.

Surface gravity of familiar bodies (Earth = 1) | |
---|---|

object | surface gravity |

Mercury | 0.378 |

Venus | 0.907 |

Earth | 1 |

Moon | 0.166 |

Mars | 0.377 |

Jupiter | 2.36 |

Europa | 0.135 |

Ganymede | 0.145 |

Saturn | 0.916 |

Titan | 0.138 |

Uranus | 0.889 |

Neptune | 1.12 |

Pluto | 0.059 |

Sun | 29.9 |

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.