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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