WHY BEING EARTH-CENTERED WHEN SEARCHING FOR LIFE IN THE COSMIC NEIGHBORHOOD?

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WHY BEING EARTH-CENTERED WHEN SEARCHING FOR LIFE
IN THE COSMIC NEIGHBORHOOD?
Carlos Alexandre Wuensche1 Claudia Lage2 Amâncio
Friaça3 Sérgio Pilling4 Heloísa Boechat-Roberty5
1Divisão de Astrofísica, - INPE 2Instituto de
Biofísica Carlos Chagas Filho - UFRJ 3Instituto
Astronômico e Geofísico - IAG/USP 4Instituto de
Química - UFRJ 5Observatório do Valongo - UFRJ
Contato alex_at_das.inpe.br
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A cosmological perspective to search of life in
the Universe...
Bennett et al., ApJ Suppl Series 2003
Ob 0.04 OT
Life building blocks come from these components...
NOT!
LETS GIVE IT UP, THEN...
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How can we define life?

• It is quite a subjective concept, but we can list
  some common characteristics (J. Schneider,
  astro-ph/9604131, 1996 Szostak et al., Nature,
  2001, Bains, Astrobiology 2005)
• Complex and diversified interactions with the
  environment
• System out of thermodynamical equilibrium
• Memory reading/recovering mechanism
• Self-replication capability

Life is a self-sustained chemical system, capable
of evolution in a Darwinian sense (Joyce 1994).
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For a practical search, restrictive hipothesis...

• What kind of complex systems?
• Liquid crystals, plasmas...
• Conservative hipothesis a chemical system.
• C, Si?
• Presence of a liquid millieu?
• H2O excelent solvant and abundant in the
  Universe
• Existence of a solid/liquid interface?
• Favours molecular interactions...

Questions 1) Does life need, necessarily, such
atoms and physical-chemical conditions? 2) Can
life develop, in another planet, under totally
different conditions?
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Most definitions tend to be EARTH-CENTERED
So, lets understand Earth model
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Lineweaver et al., Science, 303, 59 (2004)
HABITABLE ZONE (68 e 95)
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Biologically interesting elements abundance in
the Galaxy

• X/Hlog(X/H)-log(X/H)Sun.
• Components halo, thick and thin disks.
• Universe age 13 Gyr.
• Solar age 4.6 Gyr

Minimum abundance to form terrestrial planets
X/H-1.0 /- 0.3. (Lineweaver, Icarus, 151,
307, 2001)
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Stellar habitable zone
Main assumptions Surface H2O for Gyear,
geological activity, CO2-H2O-N2 atmosphere,
B-field, climate stability, resistance to
catastrophes for Gyear
R
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In the early Earth
Miller Urey, 1961
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Pre-cellular life... Where does it come from?

• Nucleic acids required!
• But NO NUCLEIC ACIDS were found in Miller Urey
  experiment.
• How could they be formed? Polymerisation of
  cyanide, which can be readily formed in a
  primitive atmosphere!
• So what? This still doesn't look much like a
  nucleic acid! However, the tetramer can be
  rearranged as follows

Saladino et al., Chem. Biochem, 2004
Images source http//www.whfreeman.com/life/upda
te/
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Pathways for biomolecule formation in space the
glycine case - Environment
ORION M42
Young stars T? 30000K ? X-rays
?1 Ori C
?
Lx 2 x1032 erg s-1 (Chandra) ne 5000 neMI
?
Excitation of rotational-vibrational levels
TRAPEZIUM - HST 2003
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Pathways for biomolecule formation in space the
glycine case - Model
PDRs Typical Features
?FUV 10-100 erg cm-2 s-1 ngas 104-105 cm-3
(107-103 cm-3) T 50-200 K (10 - 1000 K)
Tielens Hollenbach (1985) ApJ 291, 747 Schulz
etal 2001 ApJ, 549, 4441
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Measurements in space
NH2CH2COOH
Acetic acid


(-H2)
(-H2O -H)
Formic acid


Ammonia
methanolamine
Protonated Hidroxilamine
Low resistence to radiation field?
Formic acid ice/gas ratio 10000!
Ehrenfreund et al 2001 JGR , 106, E12, 33291
Whittet et al 1996 AA 315, L357
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Results from space
Through acetic acid
(2 x 1015 cm2)
(6x 1015 cm2)
Remijan etal 2002 ApJ 576, 264
Kuan etal 2004 ASR, 33, 31
Through formic acid
Liu etal 2002 Apj 576, 255
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Results from collisions at LNLS
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Recent detection of a PANH in the IRHudgins et
al. ApJ, 2005
H
N
C
Caffeine

• Spitzer detected PANHs in various galaxies,
  besides our own.
• First direct evidence for the presence of a
  prebiotic interesting compound in space.
• Presence of N is essential in biologically
  interesting compounds (clorophyle).
• The presence of a planet is no longer necessary
  for the formation of a PANH.

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Astrobiologically interesting stars and planets
Porto de Mello et al., Astrobiology, 2005
Thermal IR CO2 15 ?m O3 9.6 ?m H2O 6.3 ?m 12
?m band to microwaves CH4 7.7 ?m Window at 8-12
?m surface temperature Color temperature flux
radius (problems with clouds)
Explore the star/planet contrast in the thermal
IR (Des Marais et al 2002, Segura et al 2003)
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Any alternatives at this point???

• Other liquids may define other biochemistries
• Ammonia (Jupiter satellites), methane/ethane
  (Titan), nitrogen (silicon-oriented)
• Light (mostly IR) on the surface of Titan may
  allow photosynthesis-like processes, even at low
  temperatures.
• Chemolitotrophy possibly available in any liquid
  environment (Galilean satellites).

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OUR SOLAR SYSTEMS LIQUID POSSIBILITIES
Water-based oceans
Other liquid possibilities
water/ammonia (subsurface)
water/ammonia (surface lakes)
methane/ethane (surface lakes)
nitrogen (surface)
nitrogen (subsurface)
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Extremophiles survival chart

• Antarctica

• Temperature -15 C lt T lt 230 C
• 0 lt pH lt 12
• 0 lt Pressure lt 1200 atm
• No mandatory oxygen-based metabolism
• 20-40 Myears of dormancy
• 2 ½ years in space, at 20 K, with no nutrients,
  water and exposed to radiation (Strep. Mitis)

Hidrotermal vents
Criptoendoliths
Hot geisers and volcans
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What do we suggest?

• Carbon based, DNA-like search, in planetary
  systems
• Targeting small constituints of organic compounds
  IR/X (Pilling et al., AA 2005)
• Targeting PANHs IR (Hodges et al., ApJ 2005)
• Other alternatives (chemical/physical)
• Other liquids/fluids demand a different chemistry
  (not CHON based) due to thermodynamical
  requirements (Bains, Astrobiology 2005).
• Self-sustained ability to disturb a local
  environment (Bains, Astrobiology 2005).

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WHERE IS DNA OR ANY OF ITS RELATIVES?
The end
or the beginning?????