Transcript Why being earth-centered while seeking for life in the - IAG-Usp

2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
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: [email protected]
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
A cosmological perspective to search
of life in the Universe...
Bennett et al., ApJ Suppl Series 2003
Ωb = 0.04 ΩT
LET´S GIVE IT UP, THEN...
NOT!
Life building blocks come
from these components...
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
How can we define life?
• It is quite a subjective concept, but we can list
some common characteristics (J. Schneider, astroph/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).
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
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?
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
Most definitions tend to be EARTH-CENTERED
So, let´s understand “Earth model”
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
Lineweaver et al., Science, 303, 59 (2004)
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
HABITABLE ZONE (68% e 95%)
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
Biologically interesting elements abundance in the Galaxy
•[X/H]=log(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)
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
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
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
In the early Earth:
Miller & Urey, 1961
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
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:
Images´ source: http://www.whfreeman.com/life/update/
Saladino et al., Chem. Biochem, 2004
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
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 rotationalvibrational levels
TRAPEZIUM - HST 2003
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
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
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
Measurements in space
Methylenimine
NH2CH2COOH
Acetic acid
+
(-H2O; -H)
+
(-H2)
Formic acid
+
Ammonia
Which pathway is
more probable?
Formation via ice or
gas phase?
+
+
(-H2O; -H)
(-H2O)
methanolamine
Protonated
Hidroxilamine
Protonated
methanolamine
Formic acid ice/gas ratio ~ 10000!
Ehrenfreund et al 2001 JGR , 106, E12, 33291; Whittet et al 1996 A&A 315, L357
Low resistence to
radiation field?
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
Results from space
Through acetic
acid
(~6x 1015 cm2)
(~2 x 1015 cm2)
Kuan etal 2004 ASR, 33, 31
Remijan etal 2002 ApJ 576, 264
Through
formic acid
Liu etal 2002 Apj 576, 255
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
Results from collisions at LNLS
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
Recent detection of a PANH in the IR
Hudgins 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.
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
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)
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
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).
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
OUR SOLAR SYSTEM´S
LIQUID POSSIBILITIES
Water-based oceans
Other liquid
possibilities
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
Extremophiles
survival chart
Hidrotermal
vents
•
•
•
•
•
•
Temperature: -15° C < T < 230° C
0 < pH < 12
0 < Pressure < 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
Antarctica
(Strep. Mitis)
Criptoendoliths
Hot geisers and volcans
Thermophile bacteria
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
What do we suggest?
• Carbon based, DNA-like search, in planetary
systems
– Targeting small constituints of organic compounds – IR/X
(Pilling et al., A&A 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).
2nd Brazilian COROT Workshop - Ubatuba, Nov 6 2005
WHERE IS DNA OR
ANY OF ITS
RELATIVES?
The end…
… or the
beginning?????