14 DAY TRIAL // Scientists from the University of Arkansas (UA) have recently released a new report, claiming that the entire planet might have been formed out of meteoritic materials. They base their claims on the fact that the Earth's mantle exhibits the same set of isotopic signatures for magnesium as asteroids do, which would hint at a common origin for the two. A heated debate has been raging on in the fields of geology and astronomy over this issue, and the new pieces of evidence seem to have the potential to finally settle the matter once and for all, PhysOrg reports.
In charge of the recent study was UA Assistant Professor of Geosciences Fangzhen Teng, who worked closely with colleagues Wei Yang and Hong-Fu Zhang, both from the Chinese Academy of Sciences. Details of the work they did together appear in the latest issue of the respected scientific journal Earth and Planetary Science Letters. During the investigation, the team collected samples from various depths in the Earth's mantle, and then cross-referenced the readings they got off them with data collected from magnesium isotope readings in chondrites.
The latter are a special type of meteorites, which contains chemical elements that were formed very early in the solar system's history, from the condensation of hot gases that were left behind after the Sun was formed. “Isotopes are very sensitive to sources of material. We can use isotopes as a tool to further understand planetary origins,” Teng explains. “The samples from Earth were slightly different from one another,” he adds, but they still fitted with those collected from chondrites. “That’s very strong evidence that Earth has a chondritic magnesium composition,” Teng says.
The isotope that was mainly targeted for analysis, 26Mg, is a decay product of 26Al, a chemical that was formed in the solar system less than five million years after the Sun was born. Therefore, the amounts of 26Al in different samples from meteorites or the mantle vary with the age and other chemical properties of the respective samples. This knowledge helped the scientists tremendously in the new research, they conclude.