Scientist Finds Asteroid Fossil That May Have Caused Global Dinosaur Extinction

Frank Kyte, a geochemist from University of California atLos Angeles (UCLA), presents his analysis of the fossil meteoritein the November 19 issue of the journal Nature.

Some scientists believe that this particular worldwideextinction, which ended the Cretaceous period 65 million yearsago, was caused by the destructive impact of a comet or asteroid.Kyte found the fossil meteorite while studying the sedimentboundary layer between the Cretaceous and Tertiary eras.

Hidden in mud and buried beneath the Pacific Ocean for 65million years, the fossil is no longer composed of all of itsoriginal minerals, yet has retained its original shape andtexture.

"The fossil is a record of the original rock," said RichardLane, program manager in NSF's earth sciences division, whichfunds Kyte's research, "much like fossilized traces of dinosaurskin, or, more appropriately, like casts made from the victims ofMt. Vesuvius at Pompeii whose imprints were preserved in thevolcanic ash."

According to Kyte, it is likely that the fossil depicts theremains of a colossal asteroid, some six miles wide, whichcollided with the earth near Mexico's Yucatan peninsula. Hisfindings suggest that the original meteorite had a rockycomposition that corresponds with the makeup of asteroids, asopposed to the porous materials that would more likely be foundin a comet.

Although the fossil itself is only a tenth of an inch long,Kyte was able to deduce its origins using instruments from UCLA'selectron microprobe and neutron activation laboratories. Theseinstruments, which can identify the chemical components of agiven substance, found the fossil to be high in iridium, anelement found in relative abundance in asteroid meteorites.

In our solar system, asteroids are found orbiting the sun ina belt between Mars and Jupiter. This rocky belt of space debrisis thought to be a leftover from the time when the planets firstformed.

Kyte notes that this particular asteroid moved out of thebelt towards Earth at about 40,000 miles per hour. The resultingimpact is thought to have had devastating consequences for theworld's climate and could have led to the extinction of thedinosaurs and many other forms of life.

"Studies like Kyte's show that celestial impacts have had aprofound effect on the history of the earth," said Lane. "Onebegins to think that such catastrophic events played at least asimportant a role in shaping the earth as did more gradualprocesses."