Sunday, April 17, 2011

Comets and the Origin of Life

Format : PDF
Author :  Janaki W, Chandra W, and William Napier
Publisher : World Scientific
ISBN-13 978-981-256-635-5
ISBN-10 981-256-635-X
Size :  9 Mb

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The contemporary scientific approach to the origin of life is being shaped
within the emergent discipline of astrobiology which combines the
sciences of astronomy and biology. The widespread distribution of water
and complex organic molecules in the universe is leading scientists
towards a possibly erroneous point of view that life is not only present
everywhere but that it is readily generated in situ from non-living matter.
The idea that water and organics under the right physical conditions lead
easily to life has no empirical basis at the present time, nor indeed do we
have any definite knowledge of how such a transition occurs. On the
other hand, empirical science is now in a position to address the question
of whether life can be transferred from one astronomical setting to

The search for exosolar planets, life on Mars and elsewhere in the
solar system, and dynamical studies of how particulate material can be
transferred between potentially habitable cosmic sites, all have a bearing
on the question of our origins. We argue in this book that the production
of life in the first instance might be an exceedingly rare event but that its
subsequent evolution and dispersal are a cosmic inevitability.
The astronomical origin of the ‘stuff of life’ at the level of atoms is
beyond dispute. The chemical elements that make up living systems
were unquestionably synthesised from the most common element
hydrogen in nuclear reactions that take place in the interiors of stars.
Supernova explosions scatter these atoms into interstellar clouds, and
new stars and planets form from this material. The combination of atoms
into organic molecules can proceed in interstellar clouds via well-attested
chemical pathways, but only to a limited level of complexity that falls
well short of life. The discovery of biochemical molecules in space
material, including in meteorites, arguably crosses this threshold.

In the view of the authors of this book, the interpretation of interstellar
organic molecules as the combined product of abiotic synthesis and
biological detritus is an emerging paradigm. Inorganic processes can
scarcely be expected to compete with biology in the ability to synthesise
biochemicals, and if biology is readily distributed on an astronomical
scale, its detritus must contribute to the stuff between the stars.

The Aristotelian notion that life could arise readily from everyday
materials — fireflies from morning dew — came to be known as the
doctrine of spontaneous generation and this doctrine dominated science
well into the 19th century. When Louis Pasteur challenged this ancient
idea by showing that microbes always arose from pre-existing microbes,
the case for panspermia emerged. For if life always derives from preexisting
life, then the possibility must be considered that it predates the
Earth. This was the chain of logic followed by Lord Kelvin amongst
others in the closing decades of the 19th century.

When Fred Hoyle and one of the present authors re-examined such
arguments in the 1970s we turned to comets as the most likely
astronomical objects that were relevant to panspermia. In the past three
decades considerable progress has been made in geochemistry,
microbiology and cometary studies, all of which place comets in the
forefront of studies relevant to the origin of life. The basic structure of
the present book started as the PhD thesis of the principal author with
additional reviews and discussions that bring the whole story up-to-date.
Several astrobiology texts have been published over the past decades, but
they have been woefully short in their treatment of cometary panspermia.
The present book is intended to fill this gap.

We are grateful to the Astrobiology Research Trust and to Brig Klyce
for their unstinting support of our research into panspermia.


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