> News
> Earth's minerals have evolved over time
> Monday, 17 November 2008
> Cosmos Online
>
> SYDNEY: Geologists have found that Earth's 'mineral kingdom' has co-
> evolved with life, and that up to two thirds of the more than 4,000
> known types of minerals can be directly or indirectly linked to
> biological activity.
>
> The authors of the study, published in the current edition of the
> journal American Mineralogist, say the find could aid scientists in
> the search for life on other planets.
>
> "For at least 2.5 billion years, and possibly since the emergence
> of life, Earth's mineralogy has evolved in parallel with biology,"
> said lead author Robert Hazen. "One implication of this finding is
> that remote observations of the mineralogy of other moons and
> planets may provide crucial evidence for biological influences
> beyond Earth."
>
> "Biological influences"
>
> Hazen, Dominic Papineau and colleagues at the Carnegie Institution
> of Wasington DC, reviewed the physical, chemical, and biological
> processes that gradually transformed about a dozen different
> primordial minerals, found in ancient interstellar dust grains,
> into the thousands of mineral 'species' on the Earth today.
>
> "It's a different way of looking at minerals from more traditional
> approaches," said Hazen.
>
> "Mineral evolution is obviously different from Darwinian evolution -
> minerals don't mutate, reproduce or compete like living organisms.
> But we found both the variety and relative abundances of minerals
> have changed dramatically over more than 4.5 billion years of
> Earth's history."
>
> All the chemical elements we are familiar with were present from
> the start in the Solar System's primordial dust, but they combined
> together to form comparatively few minerals.
>
> Primordial dust
>
> Only after large bodies such as the Sun and planets were born did
> there exist the extremes of temperature and pressure required to
> forge a large diversity of mineral species, the authors said. Many
> elements were also too dispersed in the original dust clouds to be
> able to solidify into mineral crystals.
>
> As the Solar System took shape through the "gravitational clumping"
> of small, undifferentiated bodies (fragments of which are found
> today in the form of meteorites), about 60 different minerals made
> their appearance, the study says.
>
> Larger, planet-sized bodies, especially those with volcanic
> activity and bearing significant amounts of water, could have given
> rise to several hundred new mineral species. Mars and Venus - which
> the experts estimate to have at least 500 different mineral species
> in their surface rocks - appear to have reached this stage in their
> mineral evolution.
>
> However, Earth is the only planet that we know of where mineral
> evolution progressed to the next stage.
>
>
> A key factor was the churning of the planet's interior by plate
> tectonics, write the authors, the process that drives the slow
> shifting continents and ocean basins over geological time.
>
> Unique to Earth today, plate tectonics created new kinds of
> physical and chemical environments where minerals could form, and
> thereby boosted mineral diversity to more than a thousand types.
>
> What ultimately had the biggest impact on mineral evolution,
> however, was the origin of life, approximately four billion years ago.
>
> Unique perspective
>
> "Of the approximately 4,300 known mineral species on Earth, perhaps
> two thirds of them are biologically mediated," says Hazen. "This is
> principally a consequence of our oxygen-rich atmosphere, which is a
> product of photosynthesis by microscopic algae."
>
> Many important minerals are oxidized weathering products, including
> ores of iron, copper and many other metals.
>
> Microorganisms and plants also accelerated the production of
> diverse clay minerals, the study says. In the oceans, the evolution
> of organisms with shells and mineralised skeletons generated thick
> layered deposits of minerals such as calcite, which would be rare
> on a lifeless planet.
>
> Gary Ernst a geologist at Stanford University in California, USA,
> who was not involved with the research, called the study
> "breathtaking," and commented that the "the unique perspective
> presented in this paper may revolutionise the way Earth scientists
> regard minerals."
>
>
