WHY BEING EARTH-CENTERED
WHEN SEARCHING FOR LIFE IN THE
COSMIC NEIGHBORHOOD?
C. A. Wuensche (DAS – INPE)
C. A. S. Lage (IBCCF – UFRJ)
A. Friaça (IAG – USP)
S. Pilling (IQ – UFRJ)
H. Boechat-Roberty (OV – UFRJ)
[email protected]
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
A cosmological perspective to search
of life in the Universe...
Spergel et al., WMAP series, 2006
Other nonluminous components
Intergalactic gas: 3.6%
Neutrinos: 0.1%
Supermassive BHs: 0.04%
Luminous matter
Stars and luminous gas: 0.4%
Radiation: 0.005%
b
= 0.04 T
LET´S GIVE IT UP, THEN...
NOT!
Life building blocks come from these components...
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
How can we define life?
• It is quite a subjective concept, but we can list
some common characteristics (Schneider, astroph/9604131, 1996; Szostak et al., Nature, 2001; Bains, Astrobiology,
2005; Lunine 2005)
– Complex and diversified interaction with
environment
– System out of thermodynamical equilibrium
– High information content
– Memory + reading/recovering mechanism
– Self-replication
Life is a self-sustained chemical system, capable of
evolution in a Darwinian sense (Joyce 1994). the
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
For a practical search, restrictive hipothesis...
• What kind of complex systems?
– Liquid crystals, plasmas...
• Conservative hypothesis: 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?
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Most definitions tend to be EARTH-CENTERED
So, let´s understand “ Earth model”
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Lineweaver et al., Science, 303, 59 (2004)
HABITABLE ZONE (68% e 95%)
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Biologically interesting elements abundance in the Galaxy
This work: •[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)
Stellar habitable zone
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Main assumptions: Surface H2O for ~ Gyear, geological activity, CO2­H2O­N2 atmosphere, B­field, climate stability, resistance to catastrophes for ~ Gyear
R
Asplund, Grevesse & Sauval, astro-ph/0410214
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
In the early Earth:
Miller & Urey, 1961
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Pre­cellular 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
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Pathways for biomolecule formation in space:
the glycine case - Model
PDRs
Typical Features
φFUV ~ 10-100 erg cm-2 s-1
ngas ~ 104-105 cm-3 (107-103 cm3
)
T ~ 50-200 K (10 - 1000 K)
Tielens & Hollenbach (1985) ApJ 291,
747
See Pilling talk tomorrow!
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Measurements in space
Acetic acid
(-H2O; -H)
+
Methylenimine
NH2CH2COOH +
+
(-H2)
Ammonia Which pathway is
more probable?
Formation via ice or gas phase?
Protonated Hidroxilamine
+
+
(-H2O; -H)
(-H2O)
methanolamine
Protonated methanolamine
Formic acid ice/gas ratio ~ 10000!
Formic acid Ehrenfreund et al 2001 JGR , 106, E12, 33291; Whittet et al 1996 A&A 315,
L357
Low resistence
to radiation field?
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
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
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Results from collisions at LNLS
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
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.
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Astrobiologically interesting stars and planets
Porto de Mello et al., Astrobiology, 2005
Thermal IR
CO2 15 µm
O3 9.6 µm
H2O: 6.3 µm + 12 µm band to microwaves CH4 7.7
µm
Window at 8-12 µm: 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)
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
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).
• Maybe a new definition of Galactic Habitable Zone?
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
OUR SOLAR SYSTEM´S
LIQUID POSSIBILITIES
Water-based oceans
s) face)
e
k
la bsur
e
c
e a
u
n
f
s
r
(
a
eth s)
(su onia
/
a
e
i
on amm
han lake
t
m
e
/
m face
e)
/am ater
c
r
a
r
e
f
w
t
(su
su r
wa
(
en
g
o
r
ce
nit
a
f
sur
b
u
(s
n
e
rog
t
i
n
Other liquid
possibilities
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Extremophiles
survival chart
Hidrotermal vents
Antarctica
• 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 (Strep. Mitis)
Hot geisers and volcans
Thermophile bacteria
Criptoendoliths
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
Suggestions at this point?
• 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).
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
WHERE IS DNA OR
ANY OF ITS
RELATIVES?
The end…
… or the
beginning?????
I Brazilian Workshop on Astrobiology – Rio de Janeiro, March 20, 2006
ORION
M42
Pathways for biomolecule formation in space:
the glycine case (see Pilling talk tomorrow)
Young stars
T ~ 30000K X­rays
θ1 Ori C
Lx ~ 2 x1032 erg s­1 (Chandra)
ne ~ 5000 neMI
Excitation
of rotational­
vibrational levels
TRAPEZIUM - HST 2003