Gold, platinum added to theory of Earth formation

William Atkins
Monday, 13 December 2010 00:49

Science - Space

A new theory from U.S. astronomers about how the Earth was formed adds to our knowledge about our home's formative years, over 4.5 billion years ago. Impacts from extraterrestrial objects added gold, platinum, and other heavy metals to Earth during its late accretion period.

 

These extraterrestrial objects include impacts from a "limited" number of large comets and asteroids that were rich in heavy metals.

The astronomical team states that these impacts added less than 1% to the final mass of Earth, however, though small in mass, they added important metals to Earth's composition.

The U.S. researchers include William F. Bottke (Southwest Research Institute), Richard J. Walker (University of Maryland), James M. D. Day (University of Maryland and Scripps Institution of Oceanography), David Nesvorny (Southwest Research Institute), and Linda Elkins-Tanton (Massachusetts Institute of Technology).

According to Dr. 'Bill' Bottke, 'No one has a model of precisely what happened at the end of planet formation'”we've had a broad idea'”but variables such as impactor size, the approximate timing of the impacts, and how they affect the evolution of the planets are unknown."

And, "This research hopefully provides better insights into the early stages of planet formation.' [NASA: 'NASA Scientists Theorize Final Growth Spurt For Planets']

Their December 9, 2010 paper in the journal Science is called 'Stochastic Late Accretion to Earth, the Moon, and Mars' (Science 10 December 2010: Vol. 330 no. 6010 pp. 1527-1530; DOI: 10.1126/science.1196874).

The abstract to their paper states, 'Core formation should have stripped the terrestrial, lunar, and martian mantles of highly siderophile elements (HSEs).'

HSEs are elements, such as gold (Au), rhenium (Re), osmium (Os), iridium (Ir), ruthenium (Ru), platinum (Pt), and palladium (Pd), which readily bond with metallic iron (Fe).

Page two continues.