A meteorite is a piece of rock or metal that originates in outer space and survives its fiery passage through Earth’s atmosphere to land on the surface. The rarity of meteorites involves two distinct concepts: the actual number that strike the planet and the difficulty of finding and confirming them. While millions of objects enter our atmosphere daily, only a small fraction reaches the ground as recognizable extraterrestrial material. The rarity of any specific specimen is a combination of its cosmic origin and the terrestrial conditions that allow for its discovery.
The Global Frequency of Meteorite Falls
The Earth is constantly bombarded by material from space, but most of this influx is cosmic dust and tiny micrometeoroids. Scientists estimate that between 15,000 and 100,000 tons of extraterrestrial material enters the atmosphere each year. The vast majority of this tonnage consists of dust-sized particles, which vaporize high above the ground.
Objects large enough to survive atmospheric entry and become meteorites are far less common. One estimate suggests there are about 6,100 meteorite falls over the entire Earth annually. These surviving space rocks are typically small, often shrinking significantly as their outer layers melt and ablate during the intense entry process.
The Discrepancy Between Falls and Finds
A fundamental distinction exists between a meteorite “fall” and a “find.” A fall is a meteorite whose passage and impact were observed by people or sensors. A find is any meteorite discovered later without a witnessed event. This distinction explains why so few are documented.
Observed falls are significantly rarer than the true number of impacts, making up only about 1.8% of all classified specimens. The low recovery rate is primarily due to Earth’s surface composition; over 70% of the planet is covered by water, where meteorites are lost. Even those that land on continents often fall in remote, uninhabited areas or quickly blend into the native soil and rocks. Terrestrial weathering and erosion also break down and obscure meteorites over time, making them indistinguishable from ordinary rocks within a short geological period.
Geographic Factors That Concentrate Finds
The rarity of finding a meteorite is overcome in specific environments that act as natural collection and preservation sites. Hot deserts, such as the Sahara, and the cold desert of Antarctica are disproportionately successful areas for recovery. In hot deserts, the lack of vegetation and the absence of rapid weathering allow meteorites to remain visible on the surface for thousands of years.
In Antarctica, a unique mechanism concentrates the specimens, making it the most prolific recovery site on Earth. Ice sheets flow and carry embedded meteorites until they encounter an obstacle, such as a mountain range, which forces the ice upward. Strong winds then sublimate the ice from the surface, leaving the dark space rocks exposed and concentrated on “blue ice” fields, where they are easily spotted against the white background.
Rarity Based on Meteorite Classification
The rarity of a meteorite depends heavily on its classification, which reflects its composition and parent body. Meteorites are broadly categorized into stones, irons, and stony-irons. Stony meteorites, known as chondrites, are the most common type, making up about 86% of all observed falls.
The most prevalent kind are ordinary chondrites, which represent the most primitive material in the solar system. Iron meteorites, which come from the cores of ancient, differentiated asteroids, make up about 5% of falls, while stony-irons, a mix of both, are the least abundant at only about 1% of falls.
A rare group are the achondrites, which are stony meteorites that have been melted and reformed, making them look more like terrestrial volcanic rock. Achondrites, including samples blasted off the surface of the Moon and Mars, represent only around 7% to 8% of all observed falls.