New study reveals how space rocks become meteorites

Researchers have identified seven distinct phases that a space rock goes through as it falls through Earth's atmosphere and becomes a meteorite. This study, published in the journal Meteoritics & Planetary Science, examined 75 meteorite falls captured on video and in photographs. Initially, the rock experiences heat and glowing as it creates a shock wave in front of it, visible as a meteor or "shooting star."

As it descends into denser air, the rock becomes brighter, and some meteors exhibit a regular pattern of changing brightness due to rapid spinning. Melting and fragmentation, rather than evaporation and burning up, are the primary processes controlling mass loss and slowing down. In Phase 3, the rock transforms into a fireball, with most of its mass loss occurring due to melting.

The fast-moving air pulls melted material off the surface, leaving behind evaporating droplets. At around 60 kilometers above Earth, the fireball reaches Phase 4, where its brightness remains constant or grows steadily as the rock loses up to 40% of its mass from melting. Deeper in the atmosphere, higher pressure causes the rock to break apart, marking Phase 5.

As the remaining rock quickly slows down and fragments, Phase 6 begins, with a final bright flare and the scattering of pieces at higher relative speeds. The final stages involve melting and fragmentation until the last pieces stop glowing, leaving a thin fusion crust on their surfaces. These findings provide insights into the atmospheric slowdown of small, solid space rocks of different types, including those that could potentially cause airbursts as dangerous as those caused by larger asteroids.