Evolution in the Mineral Kingdom
How Life Altered Minerals on Earth and What It Means for Exobiology
Nov 13, 2008
The history of minerals in our solar system is a dynamic one. New research shows that, not unlike the animal kingdom, the mineral kingdom undergoes evolution as well.
Robert Hazen of the Carnegie Institution's Geophysical Laboratory explains this new way of looking at the mineral world: "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."
The Evolution of the Solar System and Its Minerals
The first step in the evolution of minerals in our solar system is how they changed as the planets grew. At the beginning of our solar system, as the sun and planets were forming out of the primordial dust, all the chemical elements were present but they were formed into just a few minerals. As the sun and planets took shape, temperature and pressure began its work on the elements.
Meteorites allow scientists to study what our early solar system was like. These chunks of rock are mostly unchanged from when they first formed when the solar system was young. Aoubt 60 different minerals are identified from this early stage.
Later, as planets coalesced from the multitude of fragments through gravitational clumping, minerals had new forces exerted on them. Volcanism and water transformed the surfaces of planets such as Mars and Venus, giving rise to 500 different mineral species.
How Life on Earth Has Changed the Mineral World
On Earth, minerals went through one more stage of evolution. One unique feature to Earth in our solar system is its plate tectonics. The churning of the planet's interior created new kinds of physical and chemical environments for minerals to form in.
But life has made the biggest impact on minerals, bringing the 500 different minerals up to thousands of varieties. "Of the approximately 4,300 known mineral species on Earth," says Hazen, "perhaps two-thirds of them are biologically mediated. This is principally a consequence of our oxygen-rich atmosphere, which is a product of photosynthesis by microscopic algae." Some examples of minerals that are oxidized weathering products are ores of iron and copper.
Microorganisms and plants have accelerated the production of diverse clay minerals. In particular, the ocean is a good example of how life has helped push the mineral world along. As organisms with shells and mineralized skeletons evolved they added a thick layer of mineral deposits such as calcite to the ocean floor.
What the Discovery Means to Life Elsewhere in the Universe
Understanding the way minerals evolve due to the influence of life helps scientists in the search for life elsewhere. For example, finding calcite on another planet would be a good indicator that life did or does exist there. Because minerals have been evolving parallel to the biological world, "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," Hazen says.
The study of rocks beneath your feet may someday help us to discover other lifeforms light-years away.
Source: Carnegie Institution
