Water Was Present During Birth of Earth, Study of Silver Suggests

[The Straight Story]

Water Was Present During Birth of Earth, Study of Silver Suggests

ScienceDaily (May 13, 2010) — Tiny variations in the isotopic composition of silver in meteorites and Earth rocks are helping scientists put together a timetable of how our planet was assembled beginning 4.568 billion years ago. The new study, published in the journal Science, indicates that water and other key volatiles may have been present in at least some of Earth's original building blocks, rather than acquired later from comets, as some scientists have suggested.

Compared to the Solar System as a whole, Earth is depleted in volatile elements, such as hydrogen, carbon, and nitrogen, which likely never condensed on planets formed in the inner, hotter, part of the Solar System. Earth is also depleted in moderately volatile elements, such as silver.

"A big question in the formation of the Earth is when this depletion occurred," says co-author Richard Carlson of the Carnegie Institution for Science's Department of Terrestrial Magnetism. "That's where silver isotopes can really help."

Silver has two stable isotopes, one of which, silver-107 was produced in the early Solar System by the rapid radioactive decay of palladium-107. Palladium-107 is so unstable that virtually all of it decayed within the first 30 million years of the Solar System's history.

http://www.sciencedaily.com/releases/2010/05/100513143457.htm