PLEASE NOTE:
*
CCNet 124/2000 - 30 November 2000
---------------------------------
"Our work shows that the organic matter in this soil very
probably
represents remnants of microbial mats that developed on the soil
surface
between 2.6 and 2.7 billion years ago.
This places the development of terrestrial biomass more than 1.4
billion years earlier than previously reported."
-- Hiroshi Ohmoto, The Penn State Astrobiology Center, 29
November
2000
"Does Panspermia fly? Can micro-organisms really be
transported from
one planet to another or even one planetary system to another.
Probably,
stranger things have happened. The evidence is mounting that
Panspermia
may be a viable. [...] Are comets involved in Panspermia?
Probably not."
--Matthew Genge, The Natural History Museum,
UK
"... rocks splashed into space by large impacts could
harbour live
microbes and return them to Earth later, when conditions had
settled
down. In this manner, Earth would have been re- colonised many
times.
Indeed, even today microbe-laden terrestrial rocks could return
ancient bacteria to Earth after an extended sojourn in space. The
same
mechanism would have worked even better on Mars due to its lower
surface
gravity, thus re-seeding the Red Planet with life through the
Late
Heavy Bombardment period."
-- Paul Davies, 29 November 2000
(1) ANCIENT SOUTH AFRICAN SOILS POINT TO EARLY TERRESTRIAL LIFE
Andrew Yee <ayee@nova.astro.utoronto.ca>
(2) SOIL PROVIDES CLUES TO LIFE'S ORIGINS
MSNBC News, 29 November 2000
(3) FROM PANSPERMIA TO BIOASTRONOMY
F. Raulin-Cerceau et al.
(4) ASTROBIOLOGY: EXPLORING THE ORIGINS, EVOLUTION AND
DISTRIBUTION OF LIFE
IN THE UNIVERSE
D.J. Des Marais et al.
(5) COMETARY ORIGIN OF THE BIOSPHERE
A.H. Delsemme
(6) NANOBIOLOGY: LIFE & INTELLIGENCE IN THE UNIVERSE
S. Santoli
(7) TEACHING THE ORIGIN OF THE FIRST LIVING SYSTEMS
C.M. Graz
(8) PREBIOTIC SYNTHESIS OF ADENINE & AMINO ACIDS UNDER
EUROPA-LIKE
CONDITIONS
M. Levy et al.
(9) CHRONOLOGICAL PROBLEMS IN DATING EARLY LIFE
A.P. Nutman AP et al.
(10) ORIGIN OF LIFE: AN ALTERNATIVE PROPOSAL
M. Vaneechoutte
(11) IN SUPPORT OF PANSPERMIA: AN ANTAGONISTS VIEW
Matthew Genge <M.Genge@nhm.ac.uk>
(12) LIFEBOATS IN SPACE
Michael Paine <mpaine@tpgi.com.au>
(13) OUTER SPACE AS A REFUGE FOR EARLY LIFE DURING LATE HEAVY
BOMBARDMENT
Paul Davies <pcwd@camtech.net.au>
=====================
(1) ANCIENT SOUTH AFRICAN SOILS POINT TO EARLY TERRESTRIAL LIFE
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Pennsylvania State University
Contacts:
A'ndrea Elyse Messer, (814) 865-9481(o), aem1@psu.edu
Vicki Fong, (814) 865-9481(o), vfong@psu.edu
November 29, 2000
Ancient South African Soils Point To Early Terrestrial Life
University Park, Pa. -- Remnants of organic matter in ancient
soil more than
2.6 billion years old may be the earliest known evidence for
terrestrial
life, according to a team of Penn State astrobiologists.
"Our work shows that the organic matter in this soil very
probably
represents remnants of microbial mats that developed on the soil
surface
between 2.6 and 2.7 billion years ago," says Dr. Hiroshi
Ohmoto, professor
of geochemistry and director of The Penn State Astrobiology
Center. "This
places the development of terrestrial biomass more than 1.4
billion years
earlier than previously reported."
Evidence that microorganisms flourished in the oceans since at
least 3.8
billion years ago exists, but when these microorganisms colonized
on land is
not clear. The oldest undisputed remnants of terrestrial biomass
have been
1.2 billion-year-old microfossils found in Arizona.
Examining samples taken from Mpumalanga Province, South Africa,
using a
variety of geochemical methods, the researchers report in this
week's issue
of Nature, that a paleosol dating to between 2.6 and 2.7 billion
years ago
contains organic carbon that was neither created by high
temperature fluids
nor is the remnant of later petroleum migration, but is in-situ
biological
in origin.
A paleosol is a layer of ancient soil, in this case buried and
preserved
where it formed. Because the 55-foot thick layer of soil found at
Schagen is
located between a layer of 2.7 billion-year-old serpentine and a
2.6
billion-year-old quartzite bed, the researchers can date the soil
to between
2.6 and 2.7 billion years ago. Showing that the carbon in the
soil is
biological in origin and that it accumulated during soil
formation is much
more difficult.
The researchers, who include Ohmoto; Yumiko Watanabe, Ph.D.
candidate at
Penn State and at Tohoku University, Sendai, Japan; and Jacques
E.J.
Martini, Geological Survey of South Africa, evaluated three
possibilities
for the formation of reduced carbon in the soil.
The first of these was that the carbon was graphite crystals
created when
the underlying serpentine formed under high temperatures. The
graphite then
was concentrated during the soil formation.
"The crystallinity and hydrogen/carbon rations of the
organic matter suggest
it is not of igneous or hydrothermal origin," says Ohmoto, a
faculty member
in Penn State's College of Earth and Mineral Sciences.
The second possible origin of reduced carbon is liquid
hydrocarbons
introduced after the soil formation ended. Materials introduced
after
formation should show up along fractures in the rocks.
"The organic matter is almost always concentrated in
clay-rich parts of the
rocks paralleling the ancient surface," says Ohmoto.
"Organic matter and
clays are so intimately mixed together that the size and
morphology of
individual 'grains' of organic mater can only be recognized under
electron
microscopes."
The Penn State researchers conclude that the reduced carbon was
not produced
by high heat and then incorporated into the soil as it formed,
nor was it
deposited after the soil formed by migrating petroleum. The third
possibility is that the organic carbon represents remnants of
biomats
developed on the soil surface. The researchers found that the
organic-rich
clays in the upper portion of the paleosol appeared as seams
between
fine-grained and coarse-grained layers of quartz.
"These features suggest that the organic matter in the
uppermost soil zone
is an indigenous remnant of microbial mats that developed on the
surface of
clay-rich soil during the rainy season," says Ohmoto.
"The mats were
blanketed by aerosol deposits laid down during the dry
season."
In the lower portion of the paleosol, things are less clear
because the
effects of seeping water and the dissolution and precipitation of
materials
suggest some decomposition. While identifying the organism in the
microbial
mats is difficult, the researchers are certain that they were not
photosynthetic sulfur bacteria as there is no sulfur present.
Photosynthetic
blue-green algae, however, are a likely possibility for the mat
formation
because the ancient remnants have nearly identical carbon isotope
ratios as
modern blue-green algal mats in fresh water.
The researchers are also certain that the mats formed on land,
not in the
oceans, because the carbon isotope values for the carbon in the
paleosol are
distinctly different from the organic carbon found in marine
sedimentary
rock.
"Although terrestrial bacterial communities were predicted
by previous
researchers, this is, to our knowledge, the first study
presenting several
lines of evidence for an extensive development of microbial mats
on soil
surfaces in the Archaean," says Ohmoto. "Our finding
may then imply that an
ozone shield developed before 2.6 billion years ago.
"The ozone shield would have protected land-based biological
forms from the
effects of cosmic radiation. Development of the ozone shield
requires an
oxygen-rich atmosphere. Our finding of ancient biomats on land is
an
important addition to a growing line of evidence suggesting that
the rise of
atmopsheric oxygen took place more than 2.6 billion years
ago."
The University receives research funding for this and other
efforts through
the NASA Astrobiology Institute, a research consortium of
academic,
non-profit and NASA centers including Penn State. NASA's Ames
Research
Center is the agency's lead center for astrobiology, the study of
the
origin, evolution, dissemination and future of life in the
universe.
EDITOR: Dr. Ohmoto is at (814) 865-4074 or at ohmoto@geosc.psu.edu by
email.
============
(2) SOIL PROVIDES CLUES TO LIFE'S ORIGINS
From MSNBC News, 29 November 2000
http://www.msnbc.com/news/496212.asp
Scientists say organisms reached land at least 2.6 billion years
ago
By Alan Boyle
MSNBC
Nov. 29 - Geochemists say an analysis of South African
rocks indicates that
primitive life made the jump from Earth's seas to land at least
1.4 billion
years earlier than previously thought - a claim that could have
an impact on
the search for life beyond Earth.
MICROBIAL LIFE is thought to have gotten its start at sea perhaps
3.8
billion years ago, less than a billion years after our planet's
formation,
according to current scientific theories. But when did organisms
make the
transition to land? The best evidence points to 1.2
billion-year-old
microfossils found in Arizona. But the new geological analysis,
reported in
Thursday's issue of the journal Nature, would push the frontier
back to
between 2.6 billion and 2.7 billion years ago.
Such life apparently took the form of microbial mats, layers of
cyanobacteria that were deposited on the surface to depths of a
half-inch (1
centimeter) or so, said Hiroshi Ohmoto, a geochemistry professor
at
Pennsylvania State University and director of the Penn State
Astrobiology
Center.
INDIRECT EVIDENCE
Ohmoto acknowledged that the evidence was indirect, based on a
chemical
analysis of a 55-foot-thick layer of soil in South Africa's
Mpumalanga
Province. It would be impossible to spot the individual
fossilized critters
from billions of years ago. Rather, the researchers studied the
way carbon
was deposited within that layer. "It's like a detective
story," Ohmoto told
MSNBC.com.
The distributions of various carbon isotopes, as well as the
ratios of other
chemical elements in the layer, were consistent with those of
photosynthetic
blue-green algal mats in fresh water.
The chemical analysis showed that the carbon could not have been
deposited
as the result of high-temperature processes during soil
formation, the
researchers said. They also discounted the possibility that the
carbon could
have seeped down like petroleum from later layers of rock.
Rather, the
pattern of the deposits supported the idea that ancient microbes
were swept
up from the sea by winds and fell to Earth in rainwater. During
rainy
seasons, the mats of microbes would have spread over the surface
of
clay-rich soil, Ohmoto said.
FURTHER IMPLICATIONS
He said the research implies that Earth's atmosphere would have
to have
developed a protective ozone shield relatively early in its
history.
"What our study indicates is that the rise of oxygen - which
caused the
atmosphere to build the ozone level to protect organisms from
radiation, and
allow organisms to flourish on land - probably took place much
earlier than
2.6 billion years ago," he said.
Such a finding bolsters NASA's view that ozone could serve as a
potential
atmospheric marker for the presence of life on faraway Earthlike
planets.
Within 20 years, the space agency plans to launch a probe called
the
Terrestrial Planet Finder that could analyze distant atmospheres
for such
chemical markers.
Moreover, the techniques for detecting traces of ancient life in
layers of
soil could be applied on Mars as well as Earth, he said.
"Our research establishes a new systematic approach to
identify the past
presence of life on a planet," Ohmoto said.
Penn State received funding for the research through the NASA
Astrobiology
Institute, a research consortium involving universities,
nonprofit
organizations and NASA centers. Ohmoto's colleagues in the Nature
study were
Yumiko Watanabe, a doctoral candidate at Penn State and Tohoku
University in
Japan; and Jacques E.J. Martini of the Geological Survey of South
Africa.
The researchers are planning to check other sites in Australia,
Canada and
perhaps Russia for further evidence of ancient microbial layers,
Ohmoto
said.
Copyright 2000, MSNBC
============
(3) FROM PANSPERMIA TO BIOASTRONOMY
From Panspermia to bioastronomy, the evolution of the hypothesis
of
universal life. Raulin-Cerceau F, Maurel MC, Schneider J. ORIGINS
OF LIFE
AND EVOLUTION OF THE BIOSPHERE 28: (4-6) 597-612 OCT 1998
During the 19th and early 20th centuries, ideas related to the
possible
origin in space of bioorganic molecules, or seeds, or even germs
and
organisms (and how they reached the Earth) included the
Panspermia theory.
Based on the idea of the eternity of life proposed by eminent
physicists -
such as Arrhenius and Kelvin - 'Panspermia' is mainly divided
into two
branches: lithopanspermia (transport of germs inside stones
traveling in
space) and radiopanspermia (transport of spores by radiative
pressure of
stellar light). We point out some arguments to help to understand
whether
'Panspermia' could exist nowadays as the same theory defined one
century
ago. And we wonder about the kind of evolution 'Panspermia' could
have
undergone during only a few decades. This possible evolution of
the
'Panspermia' concept takes place in the framework of the
emergence of a new
field, Bioastronomy. We present how this discipline has emerged
during a few
decades and how it has evolved. We consider its relationship with
the
progression of other scientific fields, and finally we examine
how it is now
included in different projects of space agencies. Bioastronomy
researches
having become more and more robust during the last few years, we
emphasize
several questions about new ideas and their consequences for the
current
hypothesis of 'Panspermia' and of universal life.
Addresses:
Raulin-Cerceau F, Museum Hist Nat, Grande Galerie Evolut, 36 Rue
Geoffroy St
Hilaire, F-75005 Paris, France.
Museum Hist Nat, Grande Galerie Evolut, F-75005 Paris, France.
Inst Jacques Monod, F-75251 Paris 05, France.
Observ Paris, F-92195 Meudon, France.
Copyright © 2000 Institute for Scientific Information
=============
(4) ASTROBIOLOGY: EXPLORING THE ORIGINS, EVOLUTION AND
DISTRIBUTION OF LIFE
IN THE UNIVERSE
Astrobiology: Exploring the origins, evolution, and distribution
of life in
the Universe
Des Marais DJ, Walter MR. ANNUAL REVIEW OF ECOLOGY AND
SYSTEMATICS 30:
397-420 1999
The search for the origins of life and its presence beyond Earth
is
strengthened by new technology and by evidence that life
tolerates extreme
conditions and that planets are widespread. Astrobiologists learn
how
planets develop and maintain habitable conditions. They combine
biological
and information sciences to decipher the origins of life. They
examine how
biota, particularly microorganisms, evolve, at scales from the
molecular to
the biosphere level, including interactions with long-term
planetary
changes. Astrobiologists learn how to recognize the
morphological, chemical,
and spectroscopic signatures of life in order to explore both
extraterrestrial samples and electromagnetic spectra reflected
from
extrasolar planets.
Copyright © 2000 Institute for Scientific Information
Addresses:
Des Marais DJ, NASA, Ames Res Ctr, Moffett Field, CA 94035 USA.
NASA, Ames Res Ctr, Moffett Field, CA 94035 USA.
Macquarie Univ, Sch Earth Sci, N Ryde, NSW 2109, Australia.
===========
(5) COMETARY ORIGIN OF THE BIOSPHERE
1999 Kuiper Prize Lecture: Cometary origin of the biosphere.
Delsemme AH.
ICARUS 146: (2) 313-325
Most of the biosphere was brought on the primitive Earth by an
intense
bombardment of comets. This included the atmosphere, the seawater
and those
volatile carbon compounds needed for the emergence of life.
Comets were
thrown into the inner Solar System by the strong perturbation
induced by the
growth of the giant planets' cores. The bulk of the Earth's
bombardment came
from those comets that accreted in Jupiter's zone, where the
original
deuterium enrichment had been diminished by steam coming from the
hot, inner
parts of the Solar System. This steam had condensed into icy
chunks before
their accretion into larger cometary nuclei. In contrast, comets
that
accreted in the zones of the outer giant planets kept their
interstellar
isotopic enrichments. Those comets contributed to the Earth's
bombardment
for a small amount only; they were mostly ejected into the Oort
cloud and
are the major source of the long-period comets observed today.
The
short-period comets, which come from the Kuiper Belt, should also
have the
same interstellar enrichment. The deuterium enrichment of
seawater,
accurately predicted by the previous scenario, has become one of
the best
telltales for the cometary origin of our biosphere. This cometary
origin may
have far-reaching cosmological consequences, in particular for
the origin of
life in other planetary systems, (C) 2000 Academic Press.
Addresses:
Delsemme AH, Univ Toledo, 2801 W Bancroft St, Toledo, OH 43606
USA.
Univ Toledo, Toledo, OH 43606 USA.
===========
(6) NANOBIOLOGY: LIFE & INTELLIGENCE IN THE UNIVERSE
Life and intelligence in the universe from nanobiological
principles: A
survey and budget of concepts and perspectives. Santoli S. ACTA
ASTRONAUTICA
46: (10-12) 641-647 MAY-JUN 2000
The new-born bioscience called Nanobiology has tackled the
problems of the
possibility of existence of extraterrestrial life and
intelligence and of
biosystem distribution in the Universe, as such questions
actually belong to
the realm of Theoretical Biology. The central, and yet unanswered
points of
such science have been reinvestigated by attempting knowledge and
control of
the hard-to-determine nanoscale-level classical and quantum
interactions,
which would supposedly give mechanistic, definite answers, both
informationally and energetically, to the vexing questions put by
biosystems
to science: is the "living state" a physically
definible concept, and how to
define it? Are nanoscale kinetics or even detailed mechanics
involved in the
origin of life? What about intelligence, consciousness and their
nanophysical roots? Are "life" and
"intelligence" engineerable properties,
or is any Artificial Intelligence program bound to mere
metaphors?
Self-organization, studied at the thermodynamic and the
hydrodynamic level,
showed the possibility of chemical evolution from amino acids,
probably of
cometary and/or meteoritic origin, up to spatiotemporal
organization,
autopoiesis and biological evolution, but didn't explain the
origins of
life. Questioning the uniqueness of the earthly evolutionary
chemistry is
cardinal for the ETI dilemma, as from a budgetary appraisal of
perspectives
in bionanoscale chaotic undecidable dynamics, quantum gravity and
quantum
vacuum, both "living state" and
"intelligence" look like nonlocal,
spacetime-linked cosmic phenomena. (C) 2000 Elsevier Science Ltd.
All rights
reserved.
Addresses:
Santoli S, INT, Int Nanobiol Testbed Ltd, Via A Zotti 86, I-00121
Rome,
Italy.
INT, Int Nanobiol Testbed Ltd, I-00121 Rome, Italy.
==============
(7) TEACHING THE ORIGIN OF THE FIRST LIVING SYSTEMS
Teaching the origin of the first living systems. Graz CJM.
BIOCHEMICAL
EDUCATION 26: (4) 286-289 OCT 1998
The most fundamental of questions in biology, namely that of the
origin of
living systems, is being lost to teaching and a new technique to
rekindle
interest in it must be found. This paper presents a novel idea of
teaching a
scientific concept using a poem, which describes the major
perspectives on
the origins of living systems, as the medium of instruction. All
of the
major schools of thought - chemical evolution, DNA vs. RNA,
protocell
formation, coacervates, panspermia and special creation - are
discussed. The
aim of the paper is not to be a definitive review on the origin
of living
systems, but rather to be a focal point on which to hinge further
discussion. (C) 1998 IUBMB. Published by Elsevier Science Ltd.
All rights
reserved.
Addresses:
Univ Port Elizabeth, Dept Biochem & Microbiol, ZA-6000 Port
Elizabeth, South
Africa.
===========
(8) PREBIOTIC SYNTHESIS OF ADENINE & AMINO ACIDS UNDER
EUROPA-LIKE
CONDITIONS
Prebiotic synthesis of adenine and amino acids under Europa-like
conditions.
Levy M, Miller SL, Brinton K, Bada JL. ICARUS 145: (2) 609-613
JUN 2000
In order to simulate prebiotic synthetic processes on Europa and
other
ice-covered planets and satellites, we have investigated the
prebiotic
synthesis of organic compounds from dilute solutions of NH4CN
frozen for 25
years at -20 and -78 degrees C. In addition, the aqueous products
of spark
discharge reactions from a reducing atmosphere were frozen for 5
years at
-20 degrees C. We find that both adenine and guanine, as well as
a simple
set of amino acids dominated by glycine, are produced in
substantial yields
under these conditions. These results indicate that some of the
key
components necessary for the origin of life may have been
available on
Europa throughout its history and suggest that the circumstellar
zone where
life might arise may be wider than previously thought. (C) 2000
Academic
Press.
Addresses:
Levy M, Univ Texas, Dept Mol Biol, Austin, TX 78712 USA.
Univ Calif San Diego, Dept Chem & Biochem, La Jolla, CA 92093
USA.
Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093
USA.
===========
(9) CHRONOLOGICAL PROBLEMS IN DATING EARLY LIFE
The early Archaean Itsaq Gneiss Complex of southern West
Greenland: The
importance of field observations in interpreting age and isotopic
constraints for early terrestrial evolution
Nutman AP, Bennett VC, Friend CRL, Mcgregor VR. GEOCHIMICA ET
COSMOCHIMICA
ACTA 64: (17) 3035-3060 SEP 2000
Geochemical and isotopic studies of small volumes of variably
preserved
greater than or equal to 3600 Ma rocks in gneiss complexes are
crucial for
documenting early Earth history. In the Itsaq Gneiss Complex of
the Nuuk
region, West Greenland, there is dispute whether the granitic
(sensu late)
orthogneisses dominating it are mainly products of a single ca.
3650 Ma
crust formation "super event," or whether they formed
in several unrelated
events between ca. 3850 and 3560 Ma. Which of these
interpretations of the
dates is correct has major implications regarding what the whole
rock
radiogenic isotopic record (Pb/Pb, Sm/Nd, Rb/Sr) reveals about
continental
crust formation and early terrestrial differentiation. There is
also debate
whether some West Greenland metasedimentary rocks with C-12/C-13
data
interpreted as evidence for life are greater than or equal to
3850 Ma or
only greater than or equal to 3650 Ma old. Establishing the
correct age for
these rocks is important for debates concerning early surficial
environments
and origin of life. Controversies have arisen because of
different
approaches taken by different workers, specifically with respect
to how much
emphasis is placed on held geology in interpreting dates and
isotopic data.
In this paper, field observations and sampling from low strain
zones, where
the origin and geological context of the rocks are best preserved
and
understood, are closely integrated with U-Pb zircon dates and
cathodoluminescence (CL) imagery of the zircons. This approach
shows that
most single-phase, well-preserved, meta-granitoid samples have
simple zircon
populations dominated by oscillatory-zoned prismatic grains
formed when
their host magmas crystallized On the other hand, migmatites and
some
strongly deformed-banded gneisses have much more complex zircon
populations.
The combined field evidence and zircon geochronology on the Itsaq
Gneiss
Complex demonstrate that 1) some areas contain exposed
orthogneisses formed
during multiple magmatic/thermal events between ca. 3850 and 3560
Ma and are
trot las suggested by Kamber and Moorbath, 1998) dominated by ca.
3650 Ma
granitoids containing abundant > 3650 Ma zircons inherited
from cryptic,
unexposed, older rocks; 2) abundant, greater than or equal to
3750 Ma
granitoids are present, which are locally well-preserved; 3) some
water-lain
sediments reported as showing C isotope evidence for life were
deposited as
early as 3850 Ma; 4) the whole-rock Sm/Nd isochron approach fails
to
distinguish with any confidence 3650 Ma from 3800 Ma rocks, 5)
however, it
reinforces previous indications for markedly depleted (greater
than or equal
to + 2.5 epsilon(Nd)) domains in the pre-3750 Ma mantle.
Copyright (C) 2000
Elsevier Science Ltd.
Addresses:
Nutman AP, Univ Sao Paulo, Inst Geosci, Rua do Lago 562, Post Box
11-348,
BR-05422970 Sao Paulo, Brazil.
Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT 0200,
Australia.
Hiroshima Univ, Dept Earth & Planetary Syst Sci,
Higashihiroshima 739,
Japan.
Oxford Brookes Univ, Dept Geol, Oxford OX3 0BP, England.
Atammik, DK-3912 Maniitsoq, Greenland.
=============
(10) ORIGIN OF LIFE: AN ALTERNATIVE PROPOSAL
M. Vaneechoutte: The scientific origin of life - Considerations
on the
evolution of information, leading to an alternative proposal for
explaining
the origin of the cell, a semantically closed system. CLOSURE:
EMERGENT
ORGANIZATIONS AND THEIR DYNAMICS 901: 139-147 2000
We hypothesize that the origin of life, that is, the origin of
the first
cell, cannot be explained by natural selection among
self-replicating
molecules, as is done by the RNA-world hypothesis. To circumvent
the chicken
and egg problem associated with semantic closure of the cell-no
replication
of information molecules (nucleotide strands) without functional
enzymes, no
functional enzymes without encoding in information molecules-a
prebiotic
evolutionary process is proposed that, from the informational
point of view,
must somehow have resembled the current scientific process. The
cell was the
outcome of interactions of a complex premetabolic community, with
information molecules that were devoid of self replicative
properties. In a
comparable manner, scientific progress is possible, essentially
because of
interaction between a complex cultural society and permanent
information
carriers like printed matter. This may eventually lead to
self-replicating
technology in which semantic closure occurs anew. Explaining the
origin of
life as a scientific process might provide a unifying theory for
the
evolution of information, wherebye at two moments
symbolization/encoding of
interactions into permanent information occurred: at one moment
that of
chemical interaction and at another moment that of animal
behavior
interaction. In one event this encoding led to autonomously
duplicating
chemistry (the cell), an event that possibly may be one of the
outcomes of
current scientific progress.
Copyright © 2000 Institute for Scientific Information
Addresses:
Vaneechoutte M, Univ Hosp, Dept Clin Chem Microbiol &
Immunol, Blok A, De
Pintelaan 185, B-9000 Ghent, Belgium.
Univ Hosp, Dept Clin Chem Microbiol & Immunol, B-9000 Ghent,
Belgium.
============================
* LETTERS TO THE MODERATOR *
============================
(11) IN SUPPORT OF PANSPERMIA: AN ANTAGONISTS VIEW
From Matthew Genge <M.Genge@nhm.ac.uk>
Does Panspermia fly? Can micro-organisms really be transported
from one
planet to another or even one planetary system to another.
Probably,
stranger things have happened.
The evidence is mounting that Panspermia may be a viable. There
are three
important criteria that can be met for intrasolar system
transport.
(1) Ejection from parent body
The martian (and lunar) meteorites are excellent examples that
rocks can be
ejected from the surface of one planetary body and delivered to
the surface
of another. We know of at least 14 martian meteorites and thats
probably the
tip of a very big (and rather recent iceberg). What about the
other planets?
Ejecting rocks from Venus is difficult because of its thick
atmosphere but
probably not impossible. In fact wherever meteoriticists gather
in the
search for meteorites there's always the hushed whisper
"this time we'll
find the venusian one..". Its only a matter of time
[optimism]. The Earth
too poses 'thick atmosphere, big planet' problems but there are
probably terrestrial meteorites on the surface of both Mars and
Venus. We
also know that ejecta from large impacts need not be particularly
heated or
shocked. At the very least we can be fairly certain, given their
ubiquitious
presence on the Earth's surface, that terrestrial bacteria
probably beat
humans into space by many, many millions of years.
(2) Survivability and transport.
Evidence is also mounting that bacteria could survive transport
on a
meteoroid ejected from a planet. Bacteria are the Rambos of the
animal
kingdom, you can squash them, accelerate them, heat them and put
them on ice
for millions of years and they seem to bounce back. Radiation is
probably the biggest problem for the survival of bacteria in
space since
even if spores can be dormant for long periods they won't be
viable if
strongly irradiated. However, even this does not pose an enormous
problem,
bacteria such as Dienococcus radiodurans can rapidly repair
radiation damage
to their DNA and are possibly derived from an ancestral group of
bacteria
with radioprotective capacity. In anycase radioprotection may not
be
necessary if the meteoroid is large enough to shield organisms or
if transit
times are short due to a fortuitous orbit (Murphy's law: varient
122 -
"given a long enough time even the unlikely tends to happen
at least once,
only the impossible is, well, impossible.").
(3) Entry heating.
Surviving entry heating is a piece of cake if the meteoroid
you're riding on
is not too big and not too small (at its entry velocity). The
thermoluminescence of meteorites and the survival of their low
temperature
phases clearly indicates that heating of meteoroids during
atmospheric entry
need not affect the survival of any micro-organisms hitching a
ride within.
Are comets involved in Panspermia? Probably not.
Comets are primitive bodies consisting of mixtures of volatile
ices,
refractory mineral grains and carbonaceous materials that have
never seen
the surface of a planetary body. Many of these components
probably have an
interstellar origin. That microbial life could survive on dust
grains in the
interstellar medium seems unlikely given the hard time that even
silicate
grains have in keeping intact. Many silicate grains in cometary
IDPs have
been partially amorphosed by exposure to irradiation and models
suggest that
grains are regularly vaporised and recondensed by gas drag
heating in 300
km/s supernovae shock waves. Only if bacteria evolved on the icy
comet
nuclei could their presence be explained and in the absence of
liquid water,
at these extremely low temperatures, this would seem very
unlikely.
Matthew Genge
The Natural History Museum, UK.
Some abiotic compounds with a 3.4 micron infrared band:
- Octane
- Toluene (breakdown product of macromolecular meteoritic
carbonaceous
material)
- Evaporated kerogen (reflectance spectra).
===================
(12) LIFEBOATS IN SPACE
From Michael Paine <mpaine@tpgi.com.au>
Dear Benny,
The item 'Life Under Bombardment' (CCNet 28 Nov 2000) raises the
question:
Where could life hang out in safety during those rare, massive
impact events
that caused the surface literally to boil away? Only one possible
answer was
given in the article (hydrothermal vents). I raised another
possibility in
my November 1999 Space.com story 'Your ancestors may be Martian'
Below is an extract.
Over the past year the idea that meteoroid-riding microbes could
survive for
very long period in space has been strengthened. For links see
http://www1.tpgi.com.au/users/tps-seti/reading.html#ez5
regards
Michael Paine
Lifeboats in space
Another intriguing possibility is that meteorites may have acted
as
lifeboats ("escape pods" for Star Wars fans).
Giant asteroids and comets bombarded the planets up until the
time that life
is first thought to have arisen. Following some of these impacts
the surface
of the Earth would have been sterilized by temperatures much
hotter than an
oven, and any oceans would have boiled away. Perhaps the only
escape for
organisms was to be blasted into space and the really lucky ones
returned to
the Earth when things cooled down. The same rescue system could
have worked
for any life on Mars.....
================
(13) OUTER SPACE AS A REFUGE FOR EARLY LIFE DURING LATE HEAVY
BOMBARDMENT
From Paul Davies <pcwd@camtech.net.au>
Dear Benny,
Regarding the article 'Life Under Bombardment' (CCNet 28 Nov
2000), which
raised the question: 'Where could life hang out in safety during
those rare,
massive impact events that caused the surface literally to boil
away?' I
should like to concur with Michael Paine about outer space as a
refuge.
There are actually two refugia that would be safer from large
impacts than
the hydrothermal vents on the ocean floor discussed in the above
article.
The first is the deep subsurface zone, 1 km or more down in the
Earth's
crust, which would have been beyond the reach of the heat pulses
created by
the biggest impacts. It is known that microbes inhabit this
region today.
The second is outer space. In my book 'The Fifth Miracle: the
search for the
origin of life' I suggested that rocks splashed into space by
large impacts could
harbour live microbes and return them to Earth later, when
conditions had
settled down. In this manner, Earth would have been re-colonised
many times.
Indeed, even today microbe-laden terrestrial rocks could return
ancient
bacteria to Earth after an extended sojourn in space.
The same mechanism would have worked even better on Mars due to
its lower
surface gravity, thus re-seeding the Red Planet with life through
the Late
Heavy Bombardment period.
With regards,
Paul Davies
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