Planetarymass

Planetary mass is the mass of a planet, a fundamental property that influences its gravity, atmospheric retention, internal structure, and evolutionary history. Mass is usually measured in kilograms but is commonly expressed in Earth masses (M⊕) or Jupiter masses (MJ). By convention, Earth’s mass is 1 M⊕ and Jupiter’s mass is about 318 M⊕ (1 MJ ≈ 317.8 M⊕).

Mass ranges vary by composition. Terrestrial planets like Earth and Mars typically span roughly 0.1–10 M⊕. Ice giants and gas giants extend from about 10 M⊕ to several hundred M⊕; in the Solar System, Uranus and Neptune are about 14–17 M⊕, Saturn about 95 M⊕, and Jupiter about 318 M⊕. The boundary between planets and brown dwarfs is not solely a matter of mass; a commonly cited threshold is around 13 MJ, the approximate deuterium-burning limit, but classification can depend on formation history and definitions.

Mass is often inferred through different observational methods. Radial velocity measurements yield a minimum mass (Msini) for a planet orbiting a star, while the transit method can determine a planet’s size; combining radius with mass provides bulk density. Other techniques include transit timing variations, astrometry, direct imaging, and gravitational microlensing.

A planet’s mass interacts with its radius to determine density, influences atmospheric composition and escape, drives tectonics and geologic activity, and shapes its potential habitability. In exoplanet studies, mass is essential for understanding formation and evolution, while in the Solar System it helps classify bodies and compare planetary architectures.