ASTROBIOLOGY: “ A Science Looking For a Subject ” (G. G. Simpson, evolutionary biologist)

Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) - Arcetri July 5th, 2006

ASTROBIOLOGY:“A Science Looking For a

Subject” (G. G. Simpson, evolutionary biologist)

Lapo Bettarini


OUTLINE

Just a bit of hystoryRough guide to AstrobiologyThe origin (and the meaning) of Life:

“Long term” goals“Short term” goals

What’s up with astrobiology today…A last question…


…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, Albuquerque1956: F.A. Pereira, “Introducao a Astrobiologia”, Sociedade Interplanetaria Brasilera, Sao Paulo, Brazil


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


How does LIFE begin and evolve?

Does LIFE exist elsewhere in the universe?

What is the future of LIFE on Earth and beyond?

THE STUDY OF THE LIVING UNIVERSE (NAI 2004)


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


Step 1: what we (should) know, life on earthWaterSuite 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)


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

Step 3: definition of an habitable universeHZ: Solar (and Stellar) Habitable Zone

(Kasting & Catling 2003)GHZ: Galactic Habitable Zone (Gonzalez,

Brownlee & ward 2001)


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 subductionVenus, too close to the Sun, lost its H20 owing to a moist or even runaway greenhouseMars, too small to maintain substantial geological activity over the age of the solar system, saw its CO2 atmosphere collapse


(TERRESTRIAL) HABITABILITY

Liquid waterBiogenic elements (C, H, N, O, P and S)Usable energy

Axiomatically: no life at the thermodynamic equilibriumFree energy available to drive chemical transformations

Search for abiological processes that can maintain chemical disequilibrium (for instance terrestrial geology)


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):

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)

Image credit: ESA/Mars express


LIFE ON EUROPA

Image credit: NASA/Galileo

Ocean of liquid water beneath an ice shell of 10-30 km thickGravity measurement and spectroscopy of europa’s surface: rocky body + (salty) water (induced magnetic field)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)?


Key parameters:MetallicityNearby frequency of supernovaeStellar age

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)

Spectroscopic analysis of over 80 stars known to host planets (Santos et al, 2003):


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):


Galaxy Image credit: Nasa/Ipac

7 kpc

9 kpc

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


ORIGIN OF LIFEDetermining that an environment is habitable for modern microorganisms doesn’t mean that the origin of life could have occurred in that environmentBOTTOM-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)


TOP-DOWN APPROACH (DECONSTRUCTING LIFE)Deconstructing life as we know it into the smallest possible

units that still ehxibit some characteristics of living systemsMapping 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


“LONG TERM” AND “SHORT TERM” GOALS: NASA ASTROBIOLOGY ROADMAP (2004)

7 science “long term” goalsHigh priority “short term” (3-5 years) goals

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 planetsb) Indirect and direct astronomical observations of extrasolar habitable planets

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 explorationb) Outer solar system exploration


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 catalystsb) Origins and evolution of functional biomoluculesc) Origins of energy transdunctiond) Origins of cellularity and protobiological systems

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 biosphereb) Foundations of complex lifec) Effects of extraterrestrial events upon the biosphere

3. 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 microorganisms2. Co-evolution of microbial communities3. Biochemical adaptation to extreme environments


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.

Environmental changes and the cycling of elements by the biota, communities, and ecosystemsAdaptation and evolution of life beyond the Earth

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.

Biosgnatures to be sought in solar system materialsBiosignatures to be sought in nearby planetary systems.


AND TODAY? 4 MISSIONS…

Convection, ROtation and planetary Transits (CNES)Kepler (NASA)Terrestrial Planet Finder(NASA)Darwin (ESA)


LaUNCH: October 2006 (Polar circular orbit: altitude 827 km)

The detection and the study of stars vibrations (stellar seismology)The search for extrasolar planets and more particularly the telluric planets

http://smsc.cnes.fr/COROT


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)

http://kepler.nasa.gov


http://planetquest.jpl.nasa.gov/TPF/tpf_index.cfm

Two complementary missions:TPF-C (2014): visible-light telescope with a coronograph, allowing direct spectroscopic detection of low-mass planetsTPF-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

Tinetti, California Institute of technology


LaUNCH: 2015 (L2 orbit, 1.5 milion km from the Earth)

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

http://sci.esa.int/science-e/www/area/index.cfm?fareaid=28


AND HERE? LISTEN TO GIACOMOMicrometeoroid: 10 micron < size < 1 mmAt the South Pole it is observed a largest number of these objects: variations of their properties different from what expected

Love & Brownlee 1993

Early MicroMeteorite Accretion (EMMA) scenario (Maurette et al 2000):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)


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…


SEARCH FOR EXTRATERRESTRIAL INTELLIGENCESETI 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)


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, 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-477Mars Explorer. Rovers (MER) 2004: http://mars.jpl.nasa.govLove & Brownlee,, Science 1993, 262:550“Life on Mars”, D. Bowie, Santa Monica ‘72http://kepler.nasa.govhttp://smsc.cnes.fr/COROThttp://planetquest.jpl.nasa.gov/TPF/tpf_index.cfmhttp://sci.esa.int/science-e/www/area/index.cfm?fareaid=28http://www.seti.org

Phd Journal club: ASTROBIOLOGY IN 1 HOUR (more or less) Arcetri July 5th, 2006

http://mars.jpl.nasa.gov/

http://mars.jpl.nasa.gov/

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ASTROBIOLOGY: “ A Science Looking For a Subject ” (G. G. Simpson, evolutionary biologist)

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