scholarly journals Serpentinite and the dawn of life

2011 ◽  
Vol 366 (1580) ◽  
pp. 2857-2869 ◽  
Author(s):  
Norman H. Sleep ◽  
Dennis K. Bird ◽  
Emily C. Pope
Keyword(s):  
Origin Of Life ◽  
Biological Material ◽  
Hydrothermal Vents ◽  
Chemical Potential ◽  
The Moon ◽  
Weakly Acid ◽  
The Earth ◽  
Potential Gradients ◽  
The Origin Of Life ◽  
Chemical Potential Gradients

Submarine hydrothermal vents above serpentinite produce chemical potential gradients of aqueous and ionic hydrogen, thus providing a very attractive venue for the origin of life. This environment was most favourable before Earth's massive CO 2 atmosphere was subducted into the mantle, which occurred tens to approximately 100 Myr after the moon-forming impact; thermophile to clement conditions persisted for several million years while atmospheric pCO 2 dropped from approximately 25 bar to below 1 bar. The ocean was weakly acid (pH ∼ 6), and a large pH gradient existed for nascent life with pH 9–11 fluids venting from serpentinite on the seafloor. Total CO 2 in water was significant so the vent environment was not carbon limited. Biologically important phosphate and Fe(II) were somewhat soluble during this period, which occurred well before the earliest record of preserved surface rocks approximately 3.8 billion years ago (Ga) when photosynthetic life teemed on the Earth and the oceanic pH was the modern value of approximately 8. Serpentinite existed by 3.9 Ga, but older rocks that might retain evidence of its presence have not been found. Earth's sequesters extensive evidence of Archaean and younger subducted biological material, but has yet to be exploited for the Hadean record.

Thermodynamics of life on the planetary scale

2005 ◽  
Vol 4 (1) ◽  
pp. 9-11 ◽  
Author(s):  
Minik T. Rosing
Keyword(s):  
Organic Matter ◽  
Carbon Fixation ◽  
Chemical Potential ◽  
A Priori ◽  
Planetary Scale ◽  
The Earth ◽  
Chemical Free Energy ◽  
Potential Gradients ◽  
Life Detection ◽  
Chemical Potential Gradients

The generation of organic matter from CO2 and H2O is a highly endothermic reaction. Energy for biological carbon fixation can be derived from chemical potential gradients in the environment by chemoautotrophic organisms or it can be harvested from photon energy by photosynthesis. On Earth, the plate tectonically driven carbon flux through the surface environment is of such a magnitude that the chemical free energy production within the Earth is insufficient to support conversion of any significant fraction of the carbon to organic matter through chemoautotrophy. Therefore, the chemical and isotopic fingerprints we observe in the Earth's surface environments are based on the invention of photosynthesis by life. We cannot a priori assume that life on any planet will invent photosynthesis and remote life detection should thus not be based exclusively on the expectations from our own ecosystem.

scholarly journals Conjecture and hypothesis: The importance of reality checks

2017 ◽  
Vol 13 ◽  
pp. 620-624 ◽  
Author(s):  
David Deamer
Keyword(s):  
Origin Of Life ◽  
Fresh Water ◽  
Hydrothermal Vents ◽  
Origins Of Life ◽  
Weight Of Evidence ◽  
The Earth ◽  
Alternative Hypotheses ◽  
The Origin Of Life ◽  
The Difference ◽  
Hydrothermal Fields

In origins of life research, it is important to understand the difference between conjecture and hypothesis. This commentary explores the difference and recommends alternative hypotheses as a way to advance our understanding of how life can begin on the Earth and other habitable planets. As an example of how this approach can be used, two conditions have been proposed for sites conducive to the origin of life: hydrothermal vents in salty seawater, and fresh water hydrothermal fields associated with volcanic landmasses. These are considered as alternative hypotheses and the accumulating weight of evidence for each site is described and analyzed.

Prospects for Life on Other Planets

2019 ◽  
Author(s):  
David W. Deamer
Keyword(s):  
Solar System ◽  
Origin Of Life ◽  
Hydrothermal Vents ◽  
European Space Agency ◽  
Extraterrestrial Life ◽  
Major Question ◽  
Space Agency ◽  
Planetary Bodies ◽  
The Origin Of Life ◽  
Alternative Scenarios

This book describes a hypothetical process in which populations of protocells can spontaneously assemble and begin to grow and proliferate by energy- dependent polymerization. This might seem to be just an academic question pursued by a few dozen researchers as a matter of curiosity, but in the past three decades advances in engineering have reached a point where both NASA and the European Space Agency (ESA) routinely send spacecraft to other planetary objects in our solar system. A major question being pursued is whether life has emerged elsewhere than on Earth. The limited funds available to support such missions require decisions to be made about target priorities that are guided by judgment calls. These in turn depend on plausible scenarios related to the origin of life on habitable planetary surfaces. We know that other planetary bodies in our solar system have had or do have conditions that would permit microbial life to exist and perhaps even to begin. By a remarkable coincidence, the two most promising objects for extraterrestrial life happen to represent the two alternative scenarios described in this book: An origin of life in conditions of hydrothermal vents or an origin in hydrothermal fields. This final chapter will explore how these alternative views can guide our judgment about where to send future space missions designed as life-detection missions. Questions to be addressed: What is meant by habitability? Which planetary bodies are plausible sites for the origin of life? How do the hypotheses described in this book relate to those sites? There is healthy public interest in how life begins and whether it exists elsewhere in our solar system or on the myriad exoplanets now known to orbit other stars. This has fueled a series of films, television programs, and science fiction novels. Most of these feature extrapolations to intelligent life but a few, such as The Andromeda Strain, explore what might happen if a pathogenic organism from space began to spread to the human population. There is a serious and sustained scientific effort—SETI, or Search for Extraterrestrial Intelligence—devoted to finding an answer to this question.

General discussion after session V

1988 ◽  
Vol 325 (1587) ◽  
pp. 611-618 ◽  
Keyword(s):  
Origin Of Life ◽  
Time Perspective ◽  
Applied Mathematics ◽  
Building Blocks ◽  
Living Systems ◽  
Organic Chemical ◽  
General Terms ◽  
The Earth ◽  
The Origin Of Life ◽  
Emergence Of Life

N. C. Wickramasinghe ( Department of Applied Mathematics and Astronomy, University College, Cardiff, U. K. ). The question of the origin of life is, of course, one of the most important scientific questions and it is also one of the most difficult. One is inevitably faced here with a situation where there are very few empirical facts of direct relevance and perhaps no facts relating to the actual transition from organic material to material that can even remotely be described as living. The time perspective of events that relate to this problem has already been presented by Dr Chang. Uncertainty still persists as to the actual first moment of the origin or the emergence of life on the Earth. At some time between 3800 and 3300 Ma BP the first microscopic living systems seem to have emerged. There is a definite moment in time corresponding to a sudden appearance of cellular-type living systems. Now, traditionally the evolution of carbonaceous compounds which led to the emergence of life on Earth could be divided into three principal steps and I shall just remind you what those steps are. The first step is the production of chemical building blocks that lead to the origin of the organic molecules necessary as a prerequisite for the evolution of life. Step two can be described in general terms as prebiotic evolution, the arrangement of these chemical units into some kind of sequence of precursor systems that come almost up to life but not quite; and then stage three is the early biological evolution which actually effects the transition from proto-cellular organic-type forms into truly cellular living systems. The transition is from organic chemistry, prebiotic chemistry to biochemistry. Those are the three principal stages that have been defined by traditional workers in the field, the people who, as Dr Chang said, have had the courage to make these queries and attempt to answer them. Ever since the classic experiments where organic materials were synthesized in the laboratory a few decades back, it was thought that the first step, the production of organic chemical units, is important for the origin of life on the Earth, and that this had to take place in some location on the Earth itself.

How Did It All Begin?: The Self-Assembly of Organic Molecules and the Origin of Cellular Life

2002 ◽  
Vol 11 ◽  
pp. 179-194
Author(s):  
David W. Deamer
Keyword(s):  
Origin Of Life ◽  
20Th Century ◽  
Self Assembly ◽  
Organic Molecules ◽  
Western Culture ◽  
The Self ◽  
Late 20Th Century ◽  
Cellular Life ◽  
The Earth ◽  
The Origin Of Life

Movies are the myths of late-20th century western culture. Because of the power of films likeETto capture our imagination, we are more likely than past generations to accept the possibility that life exists elsewhere in our galaxy. Such a myth can be used to sketch the main themes of this chapter, which concern the origin of life on the Earth.

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