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Where did it all begin?

21 February 2011

Hydrothermal vents above serpentine-rich rocks on the seafloor could have provided a very attractive site for the origin of life according to scientists speaking at the Royal Society. Experts are discussing the chemical origins of life on earth and its early evolution.

Serpentinite, is an olive green rock found on the seabed which is formed by the hydration and metamorphic transformation of rock from the Earth's mantle (the rocky shell between the crust and outer core). Hydrothermal vents are volcanic fissures in the earth’s surface from which geothermally heated water is released.

Professor Norm Sleep from Stanford University, who is speaking at the Royal Society’s discussion meeting, suggests that submarine hydrothermal vents above serpentinite would have produced chemical gradients of dissolved hydrogen gas and pH (acidity) that would have been very conducive to the start of life.

The first geological record of rocks on the Earth’s surface is dated at 3.8 billion years old. Studies of these rocks have shown that life on earth had evolved far beyond the RNA world (life based on ribonucleic acid) by this time. Scientists have a number of theories as to the chemical processes that may have occurred for life to have evolved in this way, including the one that Professor Sleep will be discussing.

Professor Sleep says:

“The underwater environment created from fluid rising up through chimney-like structures, sometimes called white smokers, in the serpentine-rich rocks on the seafloor would have been favourable to the dawn of life. It would have been particular so some time before the Earth’s massive CO2 atmosphere was trapped in its mantle by the movement of tectonic plates, tens to ~100 million years after the collision of two planets formed the present Earth-Moon system.

It is quite possible that life may have started using the energy from the acidity gradient of between pH 11-12 in the vent fluid and 6 in the ambient seawater with the equivalent of 1 atmosphere of dissolved CO2. The Earth passed through this state over a time of several million years, which is brief for a geologist.”

This new life inhabited tiny pores in the vent chimneys with the pores acting like cells. The organisms would later have evolved true cell membranes from the material that lined these pores.

In addition to Professor Sleep’s  talk, experts taking part in the Royal Society’s two-day discussion meeting, “The chemical origins of life and its early evolution”, will discuss how metabolic and genetic processes evolved at an early stage; whether these generated an RNA-based form of life; and how this may have led to present protein-based life.