EDITORIAL BOARD
Chairman
W.B. BURTON, National Radio Astronomy Observatory, Charlottesville, Virginia, U.S.A.
(burton@starband.net); University of Leiden, The Netherlands (burton@strw.leidenuniv.nl)
Executive Committee
J. M. E. KUIJPERS, Faculty of Science, Nijmegen, The Netherlands
E. P. J. VAN DEN HEUVEL, Astronomical Institute, University of Amsterdam,
The Netherlands
H. VAN DER LAAN, Astronomical Institute, University of Utrecht,
The Netherlands
MEMBERS
I. APPENZELLER, Landessternwarte Heidelberg-Königstuhl, Germany
J. N. BAHCALL, The Institute for Advanced Study, Princeton, U.S.A.
F. BERTOLA, Universitá di Padova, Italy
J. P. CASSINELLI, University of Wisconsin, Madison, U.S.A.
C. J. CESARSKY, Centre d'Etudes de Saclay, Gif-sur-Yvette Cedex, France
O. ENGVOLD, Institute of Theoretical Astrophysics, University of Oslo, Norway
R. McCRAY, University of Colorado, JILA, Boulder, U.S.A.
P. G. MURDIN, Institute of Astronomy, Cambridge, U.K.
F. PACINI, Istituto Astronomia Arcetri, Firenze, Italy
V. RADHAKRISHNAN, Raman Research Institute, Bangalore, India
K. SATO, School of Science, The University of Tokyo, Japan
F. H. SHU, University of California, Berkeley, U.S.A.
B. V. SOMOV, Astronomical Institute, Moscow State University, Russia
R. A. SUNYAEV, Space Research Institute, Moscow, Russia
Y. TANAKA, Institute of Space & Astronautical Science, Kanagawa, Japan
S. TREMAINE, CITA, Princeton University, U.S.A.
N. O. WEISS, University of Cambridge, U.K.
TABLE OF CONTENTS
Chapter 1
The Synthesis of the Elements and the Formation of Stars 1
M. Spaans
Chapter 2
Organic Molecules in the Interstellar Medium 17
T.J. Millar
Chapter 3
Chemistry of Protoplanetary Disks 33
Relation to Primitive Solar System Material
A.J. Markwick and S.B. Charnley
Chapter 4
Planet Formation: Problems and Prospects 67
G. Wuchterl
Chapter 5
From Elemental Carbon to Complex Macromolecular
Networks in Space 97
F. Cataldo
Chapter 6
Organic Molecules in Planetary Atmospheres 127
M. Roos-Serote
Chapter 7
Observations and Laboratory Data of Planetary Organics 149
T.L. Roush and D.P. Cruikshank
Chapter 8
The Molecular Complexity of Comets 179
J. Crovisier
Chapter 9
Kuiper belt: Water and Organics 205
C. de Bergh
Chapter 10
Interplanetary Dust Particles and Astrobiology 245
F.J. Molster
Chapter 11
The Prebiotic Atmosphere of the Earth 267
F. Selsis
Chapter 12
Early Life on Earth: The Ancient Fossil Record 287
F. Westall
Chapter 13
Highly Altered Organic Matter on Earth: Biosignature Relevance 317
B.A. Hofmann
Chapter 14
Insoluble Organic Matter in Carbonaceous Chondrites and
Archean Cherts 333
An Insight into their Structure by Electron Pamagnetic Resonance
L. Binet, D. Gourier, A. Skrzypczak, S. Derenne, and F. Robert
Chapter 15
The Chemistry of the Origin of Life 359
O. Botta
Chapter 16
A Novel Synthesis of Biomolecular Precursors 393
R. Saladino, C. Crestini, F. Ciciriello, G. Costanzo, R. Negri,
and E. Di Mauro
Chapter 17
Mars, Europa, and Beyond 415
J.D. Rummel
Chapter 18
Astrobiology in the United States 445
A Policy Perspective
D.H. Smith
Chapter 19
Astrobiology in Europe 467
A. Brack, G. Horneck, and D.Wynn-Williams
Chapter 20
Future Perspectives and Strategies in Astrobiology 477
The ISSI Team
PREFACE
The International Space Science Team: "Prebiotic matter: From the
interstellar medium to the Solar System" had its "first light" in October 2001
and has since been active in addressing interdisciplinary scientific aspects in
support of the new research discipline, Astrobiology. The team is a
consortium of 12 scientists, each representing a specific research field
crucial to revealing our origin as a consequence of the evolving Universe.
The team investigated the conditions in the Solar System, and beyond, that
allow nature to assemble the basic organics which play such an important
role in the chemical evolution that preceded biological evolution.
Some of the results from discussions held during team meetings were
published in October 2002:
"Astrophysical and Astrochemical Insights into the Origin of Life" Reports
on Progress in Physics 65, 1427-1487 (2002)
Ehrenfreund, P.; Irvine, W.; Becker, L.; Blank, J.; Brucato, J. R.; Colangeli,
L.; Derenne, S.; Despois, D.; Dutrey, A.; Fraaije, H.; Lazcano, A.; Owen, T.;
Robert, F.
In order to extend those discussions and go deeper in some important
areas, the team organized a workshop at the International Space Science
Institute in Bern, Switzerland between April 1-4, 2003 with a title:
"Astrobiology - Future Perspectives". To allow for the most fruitful
interactions, the workshop was restricted to 30 top experts in the fields that
comprise Astrobiology. This book reflects the state-of-the-art concerning
selected topics and tries to give a glimpse at the future of exciting research in
ASTROBIOLOGY, a new exciting interdisciplinary research field,
Astrobiology.
seeks to unravel the origin and evolution of life wherever it might
exist in the Universe. The current view of the origin of life on Earth is
that it is strongly connected to the origin and evolution of our planet
and, indeed, of the Universe as a whole. In order to establish a
coherent picture of processes that may have played an important role
in the chemical evolution leading to life, we have to understand the
evolution of the very early Universe. In particular, we must
investigate the formation of the first biogenic elements in stellar
interiors and during stellar mass loss and explosions. Recent
observations, balloon experiments and space missions such as the
Wilkinson – Microwave Anisotropy Probe (WMAP) have refined the
timescale of the Universe now known to be ~ 13.7 billion years old
and expected to expand forever. The first objects in the Universe
capable of ionizing gas formed about 200 million years after the Big
Bang. It is generally believed that the elemental composition of the
medium out of which the earliest stars and galaxies condensed
consisted primarily of H and He. Nonetheless, the most red-shifted
quasars, galaxies and Lyα absorbers currently observed all exhibit at
least some admixture of heavier elements, as do the most ancient stars
in our Milky Way Galaxy. Recent studies of primordial star formation
show that in the absence of heavy elements the formation of stars with
masses 100 times that of the Sun would have been favoured. Lowmass
stars could not have formed before a minimum level of heavyelement
enrichment had been reached. This enrichment has an
important effect on the fragmentation properties of a gravitationally
unstable gas, influencing the fragmentation of cloud clumps into lowmass
protostars. The formation and distribution of heavy elements
and the formation of low-mass stars contain major open questions in
the field of Astrobiology.
In the interstellar medium and circumstellar environments, heavy
elements are mixed and complex molecules and dust are formed and
continuously modified according to the physical and chemical
conditions they experience. New generations of stars and planets arise
from agglomeration of dust and gas in interstellar clouds. The last
decade has shown an impressive improvement in our understanding of
protoplanetary disks and the processes that can form terrestrial and
giant planets and the dark worlds at the outer edge of our Solar
System—the Kuiper Belt region. These disks quickly become planets
already formed planets in others. Consequently it seems possible that
in some regions, or form small bodies that can eventually collide with
both exogenous and endogenous sources of organic matter could have
provided the first building blocks of life on the early Earth and likely
merged to create the atmosphere and hydrosphere in which life
flourished. In order to develop insights into the origin and
development of life, minor Solar System objects (e.g., comets),
planetary surface processes, hydrospheres, and atmospheres remain
major targets of attention. Impacts and exogenous delivery had both
beneficial and destructive effects on the evolution of planetary
biospheres; determining the inventories of organic compounds and
other volatiles in comets, asteroids, meteorites and interplanetary dust
particles is therefore of major importance.
The transition from abiotic organic matter to entities that we define
to be “alive” is not yet understood, nor are the specific conditions on
the early Earth that must have played a major role in taking that step.
The development of multiple processes such as self-replication,
autocatalysis, Darwinian molecular selection, storage and transmission
of genetic information, molecular stability and reactivity, and
membrane formation are among the elementary steps toward
molecular evolution and life that need to be further explored. Clues to
these past events are encoded in ancient rocks, microfossils, and in the
living cells themselves. Morphological, geochemical and isotopic
biosignatures in rocks provide crucial records for unraveling the
history of primitive life. Recent discoveries of microbial life in
environments that are extreme by human standards improve our
understanding of where life may exist elsewhere in the Universe.
The search for habitats and signatures of life beyond the Earth
includes the exploration of our Solar System and the search for
extrasolar planetary systems. Currently, we know of three other
intriguing objects in our Solar System in this connection. Mars may
have had conditions suitable for the origin of life at the same time this
remarkable transition occurred on Earth. Mars may even harbour
simple forms of microbial life today, at depth, or in hydrothermal or
ice-rich regions. Recent studies of Europa imply the presence of a
liquid ocean below a thick ice crust, raising the possibility of a marine
biosphere.
Titan exhibits a rich organic chemistry (C and N) in its dense
atmosphere and may thus provide clues to the chemical evolution that
set of discoveries of the last decade has been the detection of
must precede biology. Farther away still, one of the most remarkable
numerous extrasolar planets. Continuing development of ground and
space-based telescopes is a necessary first step toward revealing
whether any of these distant worlds contain life. A spectroscopic
detection of abundant oxygen in their atmospheres would be a
compelling signal, but it is believed that the Earth had life long before
it had significant atmospheric oxygen—other indicators may provide a
key to the detection of life outside of our Solar System.
The chapters of this book discuss Astrobiology on the basis of
recent developments in relevant fields. Chapter 1 focuses on the
current cosmological concept which is manifested by recent
observations and data from space missions, and elaborates on the
consequences of primordial star formation and the time and location
of the synthesis of the first heavy elements. The formation of organic
molecules in interstellar and circumstellar environments and their
transport to protostellar disks is investigated in Chapter 2. Recent
knowledge of the chemistry occurring in protoplanetary disks, the
main physical and chemical processes associated with the formation
of solar-type stars and their accretion disks, as well as the possible
contributions to the organic inventory of primitive Solar System
bodies are discussed in Chapter 3. Following, Chapter 4 discusses
insights into planet formation. A review of the allotropic forms of
carbon in Chapter 5 provides a comprehensive view of the evolution
of this element in space and its ability to build complex molecular and
macromolecular precursors for life.
An overview of current knowledge about organic molecules in
planetary atmospheres is given in Chapter 6, which reports in-depth
on the three types of atmospheric environments that can be found in
our Solar System, namely, the highly oxidized terrestrial planet
atmospheres, the mildly reduced atmospheres of Titan, Pluto and
Triton, and the highly reduced atmospheres of the giant planets.
Interpretations of telescopic observations show that H2O-ice is
ubiquitous on surfaces throughout the outer Solar System.
Additionally, carbon-bearing molecular material is emerging as a
major component in the outer Solar System, where that material
appears entrained in H2O-ice in comet nuclei and many planetary
satellites, as well as in the more volatile N2 ice on Triton and Pluto.
Chapter 7 discusses laboratory data in relation to observations of
organics in the Solar System. By delivering prebiotic molecules to the
development of life on our planet. In order to explore this possibility,
Earth, comets could have played a role in the early phases of the
Chapter 8 presents the most recent assessment of the molecular
content of comets.
The recent discovery of a large number of Solar System bodies that
orbit the Sun beyond Neptune has identified new possibilities for the
study of primordial matter and processes in the early solar nebula.
Indeed, Kuiper Belt objects are among the most primitive solid bodies
in the Solar System though they are very difficult to study due to their
intrinsic faintness and remoteness. Chapter 9 is an overview of present
knowledge and future prospects for progress on this subject. In
complementary fashion, interplanetary dust particles are among the
most pristine materials of the Solar System presently accessible for
laboratory analysis. Current progress in the investigation of these tiny
particles, along with a description of new innovative techniques, is
reported in Chapter 10 and provides important constraints on the
evolution of our Solar System and the delivery processes of prebiotic
matter to the planetary surfaces.
The environmental conditions under which life developed on the
early Earth are unknown, and traces of Earth’s earliest history have
been recycled by the tectonic activity of our dynamic planet.
Nonetheless, in Chapter 11 the formation of the Earth, its primordial
atmosphere and the impact record are briefly described to bridge the
gap between the formation of terrestrial planets and the ancient fossil
record on Earth. The evidence for early life and its initial evolutionary
steps on Earth are linked intimately with the geological evolution of
the early Earth. While there are no records of the first appearance of
life, and the earliest isotopic indications of the existence of organisms
fractionating carbon in ~3.8 Ga (billion years) rocks from the Isua
greenstone belt in Greenland are tenuous, there are well-preserved
microfossils and microbial mats that occur in 3.5-3.3 Ga, early-
Archaean sedimentary formations from the Barberton (South Africa)
and Pilbara (Australia) greenstone belts. These are described in
Chapter 12.
On Earth, organic matter of biological origin is subjected to various
alteration processes, dominated by oxidation and/or thermal
degradation due to deep burial. Other alteration processes that may
have been rampant in the early Earth include impact metamorphism,
irradiation and thermal degradation of dissolved organic species. The
resulting molecular and carbon isotope chemistry, for the use of
implications of these transformation processes, all of which affect the
carbon compounds as biosignatures on Earth and other planetary
bodies are discussed in Chapter 13. New, sensitive techniques have
enabled us, in recent years, to elucidate the nature of extraterrestrial
macromolecular material extracted from meteorites; this is of
significant importance because the major fraction of carbon in the
interstellar medium (in dust, comets, and meteors) appears to be
incorporated in such macromolecular networks. The specific
characteristics of extraterrestrial, macromolecular carbonaceous
material are highlighted through a comparison of carbonaceous
meteorites with early-Archean cherts from the Warrawoona Group
(Australia), discussed in Chapter 14. The origin of life and remaining
unsolved questions, such as prebiotic assembly, energy transduction,
the tree of life, lateral gene transfer, and chirality are discussed in
Chapter 15. Laboratory experiments on analog and prebiotic precursor
material are described in Chapter 16.
Mars has been a central focus of interest in the context of
extraterrestrial life. The search for extinct or extant life on Mars is one
of the main goals of space missions to the red planet during the next
decade. In January 2004, the European MARS-EXPRESS went into
orbit, and two NASA Exploration Rovers, Spirit and Opportunity,
arrived safely on Mars to pursue land-based investigations of the
planet. These missions will test the planet’s ancient and current
habitability while accumulating enormous quantities of new
information. Europa is a future target for the exploration of possible
subsurface water and life therein.The search for Life elsewhere in the
Solar System and corresponding, relevant space missions to Mars and
Europa are summarized in Chapter 17. Accompanying this is a
summary of the possible prebiotic organic chemistry active on an
immense scale in the atmosphere of Saturn’s satellite, Titan, to be
explored by the CASSINI-HUYGENS mission starting in mid-2004.
Chapters 18 and 19 describe the efforts in the US and in Europe,
respectively, to introduce Astrobiology as a new, valuable scientific
discipline for research, education, and public support of science.
Future perspectives and recommendations for a successful
exploitation of interdisciplinary research ultilizing astronomical
observations, space missions, laboratory and field research, as well as
the design of instrumentation, are given in the final Chapter 20 by the
We are grateful to the International Space Science Institute in Bern,
ISSI team.
Switzerland to have hosted and supported our team over a period of
three years, and to the science of gastronomy so nicely practiced in
Bern.
Pascale Ehrenfreund, Leiden Observatory, Holland (Teamleader)
(Cosmic dust)
Luann Becker, UC Santa Barbara, USA
(Geochemistry)
Jennifer Blank, Lawrence Livermore National Laboratory, USA
(Geochemistry, Extraterrestrial delivery)
John Brucato, Observatory Napoli, Italy
(Cosmic dust)
Luigi Colangeli, Observatory Napoli, Italy
(Cosmic dust, Comets)
Sylvie Derenne, ENS de Chimie de Paris, France
(Organic chemistry of meteorites)
Didier Despois, Observatory Bordeaux, France
(Comets)
Anne Dutrey, Observatory Bordeaux, France
(Protoplanetary disks)
Bill Irvine, Univ.Massachusetts, USA
(Interstellar chemistry, Comets)
Antonio Lazcano, UNAM, Mexico
(Prebiotic chemistry)
Toby Owen, Univ. Hawaii, USA (Co-chair)
(Solar System)
Francois Robert, Lab. de Mineralogie, France (Co-chair)
(Solar nebula, Meteorites)
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