On September 3, 2004, a nearly one-million-kilogram asteroid disintegrated as it entered Earth's atmosphere, releasing as much energy as a nuclear bomb. Satellites got a close-up view of the explosion and allowed researchers to study the resulting cloud in unprecedented detail.

When meteoroids break up into tiny fragments on contact with our planet's atmosphere they leave behind a visible trail, which observers can enjoy as "shooting stars" and meteor showers. (The image is an artist's interpretation of a midsize meteor.) According to theory, most of the particles produced during the breakup are just a few nanometers across. Using infrared and light sensor readings from orbiting satellites, Andrew Klekociuk of the Australian Antarctic Division and his colleagues analyzed the makeup of the meteoric smoke produced by the September 2004 event. They found that many of the pieces of debris were in fact much larger than expected, measuring up to 20 micrometers across.

If further investigation finds that the latest results are typical, there could be implications for scientists' understanding of Earth's climate, the authors suggest. Because aerosol particles from 0.05 to one micrometer across can effectively scatter light and radiation as well as catalyze atmospheric reactions, meteoritic dust--which stays in the atmosphere for weeks to months--could play a larger role in climate forcing and ozone depletion than previously believed. A report detailing the findings is published today in the journal Nature.