Image: copyright of UWO and the University of Calgary
Last January a meteorite hurtled into Earth's atmosphere in a fiery streak, landing on the fozen surface of Tagish Lake in Canada. New research reported today in the journal Science suggests that this ancient rock may be the most primitive solar system material yet studied.
According to the report, the Tagish Lake meteorite appears to have originated in the middle of the asteroid belt as part of a meteoroid that, in its pre-atmospheric state, had a mass of about 200,000 kilograms. It belongs to a rare class of meteorites known as carbonaceous chondrites, which comprise only around 2 percent of all meteorites. Furthermore, analyses of its mineral composition and carbon and oxygen isotopes indicate that Tagish Lake represents an entirely new type of carbonaceous chondrite, the most primitive known. As such it should contain the clearest record of the solar system's most ancient events. "The more pristine meteoritic material of this type we can analyze, the better we will understand how our solar system formed and how the remnants of others came to be incorporated into it," Jeffrey N. Grossman of the U.S. Geological Survey writes in a commentary accompanying the report. "It seems likely that the Tagish Lake meteorite will be the most important recovered fall since the Allende (Mexico) and Murchison (Australia) events, both in 1969, touched off a revolution in our understanding of meteorites and what they tell us about the early solar system."