A meteorite is a natural object originating in outer space that survives passage through Earth’s atmosphere to land on the surface. These extraterrestrial fragments come from various sources, including the Moon, Mars, and the asteroid belt. Whether a meteorite feels heavy or light depends entirely on its internal structure and composition. The overall density varies widely; some meteorites are among the densest materials found, while others are nearly indistinguishable from common terrestrial rocks.
The Core Answer: Density Varies
The sensation of a rock being “heavy” or “light” for its size is determined by density, which measures mass per unit volume. Meteorites exhibit a vast range of densities because they represent material from different celestial bodies and formation histories. Density is primarily a function of the object’s metallic content versus its silicate content. This ratio is the basis for classifying meteorites into three main categories: irons, stony-irons, and stones. The density of a meteorite can range from just over 2 grams per cubic centimeter (g/cm³) for the lightest types up to 8 g/cm³ for the heaviest.
The Heavy Side: Iron Meteorites
Iron meteorites represent the high end of the density scale, typically possessing a density between 7 and 8 g/cm³. This heaviness results directly from their composition, which is overwhelmingly a nickel-iron alloy. These metallic meteorites are thought to be fragments from the cores of ancient, shattered planetesimals. Intense pressure and heat within these bodies caused the dense iron and nickel to sink to the center, similar to how terrestrial planets form cores. An iron meteorite the size of a golf ball would feel significantly heavier than a common Earth rock of the same size, which typically has a density closer to 2.7 g/cm³.
The Lighter Side: Stony Meteorites
Stony meteorites, known as chondrites and achondrites, are the most common type to fall to Earth. They are composed primarily of silicate minerals, which are the same minerals that dominate Earth’s crust and mantle. The majority of stony meteorites, called ordinary chondrites, have densities ranging from 3.0 to 3.7 g/cm³. Although this is denser than common rocks like granite, the difference is often subtle enough that the meteorite does not feel overwhelmingly heavy. Some rare types, such as carbonaceous chondrites, can be surprisingly light because they exhibit a high degree of porosity, sometimes containing up to 30% empty space.
Practical Identification: Testing the Weight
The principle of density, often called the “heft test,” is one of the most immediate tools for identifying a potential meteorite. A person performs a simple comparison by holding the suspected specimen in one hand and a known terrestrial rock of similar size in the other. If the suspected rock is an iron or a stony-iron meteorite, the difference in weight will be immediately apparent due to its high concentration of dense metal. Even ordinary stony meteorites will feel slightly denser than most common Earth rocks. This weight check is a reliable first filter, though definitive identification always requires a full laboratory analysis of the nickel-iron content.