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ASTROBIOLOGY:
“A Science Looking For a Subject”
(G. G. Simpson, evolutionary biologist)
Lapo Bettarini
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
OUTLINE
Just a bit of hystory
Rough guide to Astrobiology
The origin (and the meaning) of Life:
“Long term” goals
“Short term” goals
What’s up with astrobiology today…
A last question…
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
…JUST A BIT OF HISTORY - 1
1941: L. J. Lafleur, “Astrobiology”, leaflet 143, Astronomical Society of the
Pacific
“Astrobiology: the consideration of life in the Universe elsewhere than
in the earth”
1949: G.A. Tikhov, ”Astrobotany”, Kazakhstan SSR Acad. Of Science
Press, Alma Ata, Kazakhstan (in russian)
1953: G.A. Tikhov, “Astrobiology”, Molodaya Gvardia Press, Moscow (in
russian)
1953: H. Struhold, “The green and the red planet: a physiological study
of the possibility of life on Mars”, Univ. of New Mexico Press,
Albuquerque
1956: F.A. Pereira, “Introducao a Astrobiologia”, Sociedade
Interplanetaria Brasilera, Sao Paulo, Brazil
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
Biogenic-looking features in ALH84001 Martian meteorite. Image credit:
NASA
…JUST A BIT OF HISTORY - 2
1975-6: first 3 biological experiments on Mars made by means of Viking 1
and Viking 2…inconclusive…
1996: liquid water interior of Europa (Galielo Orbiter)
1996: INDICATORS OF PRIOR LIFE ON MARS
1996: first astrobiology scientific conference
1998: NASA Astrobiology Institute and the Nasa Astrobiology Roadmap
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
THE STUDY OF THE LIVING UNIVERSE (NAI 2004)
How does LIFE begin and evolve?
Does LIFE exist elsewhere in the universe?
What is the future of LIFE on Earth and beyond?
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
SO, FIRST OF ALL…WHAT‟S LIFE ?
No generally accepted definitions (robust counter-
examples):
List of failed attempts (C. Sagan 1970)
METABOLIC definitions imply the growth and the
reproduction through chemical reactions….for
example…FIRE!!!!
THERMODYNAMIC definitions imply the creation and the
support of a local order…for example…CRYSTALS!!!!
(that may also reproduce)
LEONARDO DA VINCI‟s DILEMMA: What‟s WATER?
We need a theory of the NATURE of the living systems
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
Step 1: what we (should) know, life on earth
Water
Suite of so-called “biogienic” elements (carbon)
Usable source of energy (light and/or chemical energy)
Step 2: what we (would like to) know, “other” lifes
Other polar solvents (liquid ammonia, Barrow & Tipler 1986) or
non-polar solvent (methane or ethane, Lunine, Stevenson &
Young 1983)
Silicon-based chemistry (Feinberg & Shapiro 1980)
EM fields, gravity, kinetic energy… (Schulze-Makuch & Irwin
1984)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
Step 3: definition of an habitable universe
HZ: Solar (and Stellar) Habitable Zone (Kasting &
Catling 2003)
GHZ: Galactic Habitable Zone (Gonzalez, Brownlee &
ward 2001)
Step 4: three ways to search for extraterrestrial life
In situ (and ultimately, sample return) searches within the
solar system
The spectral examination of solar and extrasolar planetary
atmospheres for chemical evidences of life
Searches for evidence of extraterrestrial technology
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
A stabilizing feed back driven by plate
tectonics on Earth has allowed CO2 and H20
on Earth to maintain greenhouse heating in
just the range to permit surface oceans to
exist through geological time. Carbon dioxide
levels in the atmosphere are mantained within
the range yielding surface temperatures that
allow liquid water via a negative feedback
involving CO2 removal by rainfall, precipitation
as carbonates, and resupply to the
atmosphere due to volcanism subsequent
carbonate subduction
Venus, too close to the Sun, lost its H20
owing to a moist or even runaway
greenhouse
Mars, too small to maintain substantial
geological activity over the age of the solar
system, saw its CO2 atmosphere collapse
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
(TERRESTRIAL) HABITABILITY
Liquid water
Biogenic elements (C, H, N, O, P and S)
Usable energy
Axiomatically: no life at the thermodynamic equilibrium
Free energy available to drive chemical transformations
Search for abiological processes that can maintain chemical
disequilibrium (for instance terrestrial geology)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
LIFE ON MARS (Bowie 1971)
Nearly geologically dead (Acuna
et al 1999)
Changes in solar insolation:
Milankovitch cycles (Head et al
2003, Howard et al 2002):
Image credit: ESA/Mars
express
Mars Exploration Rovers: discovery of sulfate salt deposits in Meridiani
Planum = considerable volume of liquid water; sulfur-rich compounds
and layered deposits = liquid water activity (MER 2004)
Ground-based spectroscopy and Mars express spacecraft: CH4
inhomogeneously distribution = methane active source =
methanogenesis by oases of living subterrean organisms? Abiogenic
origin? (Krasnopolsky et al 2004)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
LIFE ON EUROPA
Ocean of liquid water beneath
an ice shell of 10-30 km thick
Gravity measurement and
spectroscopy of europa’s
surface: rocky body + (salty)
water (induced magnetic field)
Image credit:
NASA/Galileo
tidal flexing (heating) = enough internal energy dissipation to maintain
most oaf this ice layer as liquid water (Chyba & Phillips 2005)
Cometary collisions = delivering of sufficient biogenic elements
(Pierazzo & Chyba 2001)
Photosynthesis = difficulty of mantaining a large biomass on Europa
(Gaidos et al 1999)
Chemical disequilibrium due to charged-particle radiation (chyba &
Phillips 2005) or hydrothermal vents (McCollom 1999)?
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
Key parameters:
Metallicity
Nearby frequency of
supernovae
Stellar age
Spectroscopic analysis of over 80 stars
known to host planets (Santos et al,
2003):
No variation in the comparison between 20 MJUP > M > 10 MJUP with <
10 MJUP and between single planet systems with multiple planet
systems (or planets in binary sistems)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
850 well-observed stars analysis: strong correlation between <[Fe/H]>
and Doppler-detected extrasolar planets (Fischer & Valenti 2005):
Planet formation, thus system habitability, should increase with
decreasing galactic radius, but supernovae may have a severe effect
on habitable planet (Lineweaver, Fenner & Gibson 2004):
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
9 kpc
7 kpc
Galaxy Image credit:
Nasa/Ipac
Coupling the accumulation of
metals in the Milky Way Galaxy
with sterilizing supernovae
explosions and taking 4 ± 1 Gyr
timescale for the evolution of
complex life
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
ORIGIN OF LIFE
Determining that an environment is habitable for modern microorganisms
doesn’t mean that the origin of life could have occurred in that
environment
BOTTOM-UP APPROACH (BUILDING LIFE)
“Primordial soup” (miller & Urey 1953) or “warm pond” (darwin 1871)
PREBIOTICALLY SIMPLE MOLECULES (CH4, NH3) +
Energy (spark discharge, UV irradiation, immpact shock) =
AMINO ACIDS or NUCLEIC ACID BASES
COMPARTMENTALIZATION: endogenous and/or exogenous sources
(Deamer 1997)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
TOP-DOWN APPROACH (DECONSTRUCTING LIFE)
Deconstructing life as we know it into the smallest possible units that
still ehxibit some characteristics of living systems
Mapping the genetic relationship of all life on Earth in an attempt to
elucidate the properties of the last common ancestor
First chicken or egg? mmmm…actually together
RNA ENZYME discovery (R.W. Holley 1964)
(catalytic activity + information storage)
Properties: self-splice and catalyzation of proteins syntesis
(Cech 1993)
Reveal the minimal set of genes necessary for complete cellular
functionality
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
“LONG TERM” AND “SHORT TERM” GOALS: NASA
ASTROBIOLOGY ROADMAP (2004)
7 science “long term” goals
High priority “short term” (3-5 years) goals
1. Understand the nature and the distribution of habitable envirnments in the universe. Determine
the potential for habitable planets beyond the solar system, and characterize those that are
observable
a) Models of formation and evolution of habitable planets
b) Indirect and direct astronomical observations of extrasolar habitable planets
2. Explore for past or present habitable environments, prebiotic chemistry, and signs of life
elsewhere in our solar system. Determine any chemical precursors of life and any ancient
habitable climates in the solar system, and characterize any extinct life, potential habitats, and
any extant life on Mars and in the outer solar system
a) Mars exploration
b) Outer solar system exploration
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
3. Understand how life emerges from cosmic and planetary precursors. Perform observational,
experimental, and theoretical investigations to understand the general physical and chemical
principles underlying the origins of life
a) Sources of prebiotic materials and catalysts
b) Origins and evolution of functional biomolucules
c) Origins of energy transdunction
d) Origins of cellularity and protobiological systems
4. Understand how past life on Earth interacted with its changing planetary and solar system
environment. Investigate the historical relationship between Earth and its biota by integrating
evidence from both the geologic ad biomolecular records of ancient life and its environments.
a) Earth’s early biosphere
b) Foundations of complex life
c) Effects of extraterrestrial events upon the biosphere
5. Understand the evolutionary mechanisms and environmental limits of life. Determine the
molecular, genetic, and biochemical mechanisms that control and limit evolution, metabolic
diversity, and acclimatization of life
1. Environment-dependent, molecular evolution in microorganisms
2. Co-evolution of microbial communities
3. Biochemical adaptation to extreme environments
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
6. Understand the principles that will shape the future of life, both on Earth and beyond. Elucidate
the drivers and effects of ecosystem change as a basis for projecting likely future changes on
time scales ranging from decades to millions of years, and explore the potential for microbial life
to adapt and evolve in environments beyond its planet of origin.
1. Environmental changes and the cycling of elements by the biota, communities, and
ecosystems
2. Adaptation and evolution of life beyond the Earth
7. Determine how to recognize signatures of life on other worlds and on early Earth. Identify
biosignatures that can reveal and characterize past or present life in ancient samples from Earth,
extraterrestrial samples measured in situ, samples returned to Earth, remotely measured
planetary atmospheres and surfaces, and other cosmic phenomena.
1. Biosgnatures to be sought in solar system materials
2. Biosignatures to be sought in nearby planetary systems.
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
AND TODAY? 4 MISSIONS…
Convection, ROtation and planetary Transits
(CNES)
Kepler (NASA)
Terrestrial Planet Finder(NASA)
Darwin (ESA)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
http://smsc.cnes.fr/CORO
T
The detection and the study of stars vibrations (stellar
seismology)
The search for extrasolar planets and more particularly the
telluric planets
LaUNCH: October 2006 (Polar circular orbit: altitude 827
km)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
http://kepler.nasa.go
v
Search for and monitor transients “around” 105 stars for 4
years: frequency of Earth-size worlds as well as the semimajor
axes of these planets‟ orbits (it covers a wide range of planet
sizes, orbital distances and stellar types)
LaUNCH: Winter 2008 - Spring 2009 (Earth-trailing heliocentric
orbit, T ~ 372.5; “worst case” drift ~ 0.5 AU)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
http://planetquest.jpl.nasa.gov/TPF/tpf_index.cf
m
Two complementary missions: Tinetti, California Institute of
technology
TPF-C (2014): visible-light telescope with a coronograph,
allowing direct spectroscopic detection of low-mass planets
TPF-I (2020): mid-infrared observatory with four formation-flying
3.5m mirrors that will use nulling interferometry for investigating
the atmospheric chemistry and possible biosignatures on
detected planets
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
http://sci.esa.int/science-
e/www/area/index.cfm?fareaid=28
Darwin will use a flotilla of three space
telescopes, each at least 3 metres in diameter,
and a fourth spacecraft to server as
communications hub. The telescopes will operate
together to scan the nearby Universe, looking for
signs of life on Earth-like planets
LaUNCH: 2015 (L2 orbit, 1.5 milion km from the
Earth)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
AND HERE? LISTEN TO GIACOMO
Micrometeoroid: 10 micron < size < 1 mm
At the South Pole it is observed a largest
number of these objects: variations of their
properties different from what expected
Early MicroMeteorite Accretion (EMMA)
scenario (Maurette et al 2000): Love & Brownlee 1993
micrometeorites played an important role in
atmospheric and oceanic formation and in the
appearence of life on Earth. They are rich of
carbon compounds…
Niche for life (reactors)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
A last question: intelligence in the universe
Drake equation (drake, 1961):
Fermi problem: “though the answer may be difficult to guess a priori, by
breaking the calculation down into a product of numbers whose order of
magnitude may be estimated, one can make a credible estimate…but L?
Anthropic argument: comparison between the lifetime of a main-sequence
star like our Sun and the timescale for biological evolution (carter 1983)
Enrico Fermi asked: “Don’t you ever wonder where everybody is?” Several
solutions, but no certainties…
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
SEARCH FOR EXTRATERRESTRIAL INTELLIGENCE
SETI Institute (1984)
The mission of the SETI Institute is to explore, understand and explain the
origin, nature and prevalence of life in the universe (LITU).
The SETI Institute is a private, nonprofit organization (externally funded
with outside grants, often by NASA and NSF) dedicated to scientific
research, education and public outreach.
Project Phoenix: scanning of billions of microwave frequencies with narrow
bandwidths while allowing for frequency drift and rigorously excluding
terrestrial interference:
SO FAR (over a decade): 460 days of observing times ~ 103 sun-like stars
IN THE FUTURE (over a decade): 105 - 106 stars (Allen Telescope Array)
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th,
2006
REFERENCES
“Astrobiology: the study of the living universe”, C.F. Chiba & K.P. Hand, Annu. Rev. Astrophys. 2005,
43:31-74 (and references therein)
“The NASA astrobiology roadmap”, D.J. Marais et al, astrobiol. 2003, 3: 219-235
“The NASA astrobiology institute: early history and organizzation”, B.S. Blumberg, astrobiol. 2003,
3: 463-470
“Lectures in Astrobiology: volume 1”, M. Gargaud, B. Barbier, H. Marvin & J. Reisse, Springer-verlag
Berlin 2005
“The galactic habitable zone: galactic chemical evolution, G. Gonzalez, D. Brownlee & P. Ward,
Icarus 2001, 152:185-200
“Statistical properties of exoplanets II: Metallicity, orbital parameters and space velocities”,
N.C. Santos, G. Israelian, M. Mayor, R. Rebolo, astron. & astrophis. 2003, 398:363-376
“The planet-metallicity correlation”, D.A. Fischer & J. Valenti, ApJ 2005, 622:1102-1117
“The galactic habitable zone and the age distributionof complex life in the Milky way”, C.H.
Lineweaver, Y. Fenner & B.K. Gibson, science 2004, 303:59-62
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less)
Arcetri July 5th, IN 1
Phd Journal club: ASTROBIOLOGY 2006 HOUR (more or less) - Arcetri July 5th,
2006
REFERENCES
“Evolution of an habitable planet”, J.F. Kasting & D. Castling, Annu. Rev. Astron. Astrophys 2003,
41:429-463
“Letter to Hooker” in “Search for the universal ancestors”, Darwin C., ed. H. Hartman, J.G. Lawless,
P. Morrison, NASA SP-477
Mars Explorer. Rovers (MER) 2004: http://mars.jpl.nasa.gov
Love & Brownlee,, Science 1993, 262:550
“Life on Mars”, D. Bowie, Santa Monica „72
http://kepler.nasa.gov
http://smsc.cnes.fr/COROT
http://planetquest.jpl.nasa.gov/TPF/tpf_index.cfm
http://sci.esa.int/science-e/www/area/index.cfm?fareaid=28
http://www.seti.org
Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less)
Arcetri July 5th, IN 1
Phd Journal club: ASTROBIOLOGY 2006 HOUR (more or less) - Arcetri July 5th,
2006
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