This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: What happens to a space rock as it falls through Earth's atmosphere and becomes a meteorite? By studying 75 meteorite falls captured on video and in photographs, researchers identified seven distinct phases in the journey from space rock to meteorite.
Their findings show that melting and fragmentation, rather than simply evaporation and "burning up," control how a rock loses mass, slows down and ultimately reaches the ground. The journal Meteoritics & Planetary Science published these findings. "We used to think that solid rocks would evaporate from the enormous heat and brilliant light generated in collisions with air," said meteor astronomer and lead author Dr.
Peter Jenniskens of the SETI Institute and NASA Ames Research Center. "We found instead that first melting and then fragmentation control how a rock loses mass." The team found that a fireball goes through seven stages as it moves through Earth's atmosphere. Each stage is shaped by different physical processes.
Phase 1 starts high in the atmosphere, when the air is dense enough to create a shock wave in front of the falling rock. Collisions with air molecules heat the rock and the gas around it until they glow. This is what we see as a meteor or "shooting star." As the rock falls into thicker air, Phase 2 begins and the meteor gets brighter.
Some meteors show that the rock is spinning rapidly by changing brightness in a regular pattern. The fastest-spinning rocks in the study made a full turn every 0.5 to 5 seconds. In Phase 3, the meteor gets much brighter and turns into a fireball.
The researchers found that melting now causes most of the rock's mass loss. The fast-moving air pulls melted material off the surface, leaving droplets behind that keep evaporating. "In the laboratory, we cannot generate the amount of radiation that occurs in a natural atmospheric entry at those speeds," said Eric Stern, formerly at NASA Ames and now chief scientist at Hyperspace Technologies Inc.
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