First Steps in the Origin of Life in the Universe
EuroConference
Sixth Trieste Conference on Chemical Evolution
Post-deadline summaries
Keynote Lectures
The submarine hot spring hypothesis for the origin of life on Earth
John B. Corliss
Systems Laboratory
Environmental Science and Policy
Central European University
Budapest, Hungary
corliss@syslab.ceu.hu
http://www.syslab.ceu.hu/~corliss
36-1-327-3887
A viable model for the origin of life on earth must meet several challenges:
(1) It must describe a continuous process leading from simple
molecules to evolved living organisms.
(2) It must be consistent with our experimental and theoretical
understanding of the abiotic synthesis of complex organic compounds
from simple compounds of the necessary elements.
(3) It must explicitly account for the self-oranization of these
components leading to non-living replicating systems and in turn
to the emergence of highly "improbable" complex living
systems
(3) It must be consistent with the record of early earth environments
as recorded in Archaean Greenstone Belts.
(4) It must make contact with models for the subsequent evolution
of life based on the historical record found in the conservative
biopolymers of modern organisms.
The hot spring hypothesis meets these challenges:
(1) Origin of life research is often highly focused on single aspects of the problem, e.g. prebiotic chemistry, molecular self-organization, the origin of the genetic code, the origin of metabolic pathways, or early cellular evolution. The hot spring model integrates the results of much of this research into a holistic model.
(2) Submarine hot springs are powerful dissipative systems
in which the necessary components are constrained to follow unique
phase space trajectories. This path can lead to the assembly of
complex organic molecules and organized structures which are thermodynamically
inaccessible
to near-equilibrium systems or unconstrained chaotic dissipative
systems.
These fluid trajectories are found in the hydrothermal systems
which produce low temperature vents, the Galapagos Rift vents,
and similar vents, populated by the same unique living communities
of clams, mussels, tube
worms, which typically surround high temperature "smoker"
vents.
(3) This fluid trajectory includes three stages: First, the
Cracking Front at which seawater reacts with high-temperature
rock near the magma body,
Second the fluids rise, cooling by mixing with descending seawater,
through an extensive systems of clay-lined fractures in the overlying
crust, to emerge at ~ 20 deg C into the bottom water. Where vents
are sediment-covered, the fluids flow through large hydrothermal
mounds, or hydrothermal stromatolites, consisting of laminated
oxides and silicates
precipitated from the fluids.
(3) Archaean greenstone belt rocks clearly show the pervasive
influence of submarine hot spring activity on the Archaean ocean
crust, the chemical Archaean oceans. Some of the earliest known
fossils of living organisms are found in
deposits clearly related to submarine hot spring activity.
(4) The early evolution of living systems, from progenote to
archaebacteria, eubacteria and eucaryotic cells, as determined
by sequencing of 16S-ribosomal RNA from modern organisms, is totally
consistent with the natural evolutionary progression in the hot
spring environment. Fractures within the rock in which high temperature
fluids are mixing with cold descending seawater provide a natural
environment for the emergence of chemosynthetic metabolic pathways
characteristic of the
Archaea.
(5) The hydrothermal mounds at the sea-floor interface provide the evolutionary constraints - a redox gradient, and, in shallow seas, a flux of solar radiation - which lead naturally to the diverse metabolic and symbiotic behaviors found in the eubacteria. Such laminated microbial communities were the first ecosystems. They form an ideal environment for the emergence of the ultimate symbiosis represented by the eucaryotic cell.
Likelyhood of transport of life between the planets of our solar system or between different solar systems
Gerda Horneck
DLR, German Aerospace Center, Institute of Aerospace Medicine,
Radiation Biology, Koeln, Germany, gerda.horneck@dlr.de
More than a century ago H. Richter and later on S. Arrhenius
formulated the theory of Panspermia which postulates that microscopic
forms of life, for example spores, can be propagated in space
driven by the radiation pressure of the sun. Since its formulation
this theory has been subjected to several criticisms, especially
that it can not be experimentally tested and that spores will
not survive long-time exposure in the hostile environment of space.
Recent discoveries have given new support to revisit the theory
of Panspermia, such as the evidence that SNC meteorites originated
from Mars, the high UV resistance of microorganisms at the low
temperatures of deep space, and the high survival rate of bacterial
spores over extended periods in space. Although it will be difficult
to prove that life has been transported through our solar system,
the chances for the different steps of the process to occur can
be estimated. These include (i) the escape process, i.e. removal
to space of biological material which has survived being lifted
from the surface to high altitudes; (ii) the interim state in
space, i.e. survival of the biological material over time scales
comparable with the interplanetary passage; (iii) the entry process,
i.e. non-destructive deposition of the biological material on
another planet. In the endeavour to disentangle the network of
potential interactions of the parameters of space (step (ii) in
the scenario), methods have been applied to separate each parameter
of space (e.g., vacuum, UV- and ionizing radiation, temperatures
extremes) and to investigate its impact on biological integrity,
applied singly or in controlled combinations. It has also been
shown that resistant microbes can survive step (i) i.e. the impact
of a large meteorite, which is considered as the most feasible
process for reaching escape velocity on Mars or the Earth. A comprehensive
experimental and theoretical study of the probability of microbes
surviving the different steps of a hypothetical trip through the
solar system concluded that radiation-resistant microbes could
survive a journey from one planet to another in our solar system
(e.g., from Mars to Earth or vice versa) if they were shielded
by a substantial layer of meteorite material. However, for transport
of life from one solar system to another the chances seem to be
very low.
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Posters P30, P31
John B. Corliss
Systems Laboratory
Environmental Science and Policy
Central European University
Budapest, Hungary
corliss@syslab.ceu.hu
http://www.syslab.ceu.hu/~corliss
36-1-327-3887
The posters will present the submarine hot spring hypothesis in a series of steps utilizing graphics illustrating the phases of the hypothetical process, and color photos from the Galapagos Rift warm spring systems. The intent will be to provide a background for individual discussions of questions about the hypothesis and ideas for future research.
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VIDEO
V1. John B. Corliss, Central European University, Budapest, Hungary
The Video presentation will include a video and photos taken
on the original Galapagos dives. The presentation will focus on
what is known in some detail about modern submarine hot springs,
carefully making the distinction between the low-temperature vents
and high-temperature smokers
which are irrelevant to the hypothesis. Discussion will include
the chemistry of the fluids from the Galapagos and other samples,
the nature of the mixing gradient, bacterial samples and the bactyerial
communities, filter samples from the fluids, and possibilities
for future work.