Habitabilidade

Eixos de pesquisa astrobiológica • História da complexidade cósmica

• Universo molecular

• Habitabilidade

• Sistema Solar

• Exoplanetas

• Extremófilos

• Origens da vida

• Bioassinaturas

• Evolução das biosferas

• Ação humana na Terra e além

HabitabilityHomes for Life

• Conditions for the rising of life (conditions for the development of complexity – complex chemistry, long time spans, critical prebiotic mass)

• Conditions for the life to survive (against catastrophes of geological or astronomical origin)

Three Levels of Habitability

• Biophilic Cosmos

• Galactic Habitable Zone

• Stellar Habitable Zone

On the most basic level

The “Goldilocks zone”in planetary systems

The Stellar Habitable Zone

Stellar habitable zone

R

Main assumptions: Surface H2O for ~ Gyear, geological activity, CO2-H2O-N2 atmosphere, B-field, climate stability, resistance to catastrophes for ~ Gyear

On the intermediate level

The “Goldilocks zone”for galaxies

The Galactic Habitable Zone

orGalaxies as home for life

On the most universal (or “multi-universal”) level

-The Universe as a “Goldilocks problem”

Cosmic Habitability

A Biophilic Universe

Martin ReesOur Cosmic Habitat

A universe hospitable to life – what we may call a biophilic universe – has to be very special in many ways. The prerequisites for any life – long-lived stars, a period table of elements with complex chemistry, and so on – are sensitive to physical laws and could not have emerged from a Big Bang with a recipe that was even slightly different.

APENAS SEIS NÚMEROS

• N = 1036, a razão da força eletromagnética para a força gravitacional entre dois prótons.

= 0.007, medida da intensidade da energia de ligação entre os neutrons e prótons dentro do núcleo atômico.

= 0.3, quantidade de matéria no Universo = 0.7, quantidade de energia em vácuo no

Universo • Q = 1/100 000, medida da profundidade média das

flutuações de densidade do Universo• D = 3, número de dimensões do espaço

A cosmological perspective to search of life in the Universe...

Life building blocks come

from these components...

Ωb = 0.04 ΩT

Bennett et al., ApJ Suppl Series 2003

Qual a Origem dos Elementos Quimicos?

• Nucleossíntese primordial é insuficiente• Não ultrapassa o numero de massa 8• Produz apenas Hélio, Deutério e Lítio• Do Carbono em diante, e necessaria a

nucleossíntese estelar!• O nascimento das estrelas é essencial para o

surgimento do C e da química necessária à vida!!!

NUCLEOSSÍNTESE PRIMORDIAL

NUCLEOSSÍNTESE ESTELAR

Supernovas• Morte Violenta!• Mais de um tipo:

– Ia: sistemas binários– II: estrelas de alta massa

• SNII: queima nuclear até Fe• Colapso gravitacional• Núcleo estrela de

neutrons• Camadas exteriores

supernova• O, elementos , C, (Fe), (N)• Tempos: Manos (ou anos

para as hipernovas primevas)

SN1987A (David Malin and the Anglo Australian Observatory)

Nebulosas Planetárias• O Sol vai morrer assim!• Estrelas com massas

menores que 8 vezes a massa do Sol

• Núcleo anã branca• Camadas exteriores

nebulosa planetária • C, N• Tempos: até varios Ganos• Promovem as condições

pré-bióticas.

Universo Orgânico!

• 0.5 % da matéria bariônica “visível” está na forma molecular. (Fraser, McCoustra & Willians, 2002, A&G, 43, 2.11).

• 148 Moléculas detectadas no espaço 148 Moléculas detectadas no espaço (~50% orgânicas: CHON).(~50% orgânicas: CHON).

Como as biomoléculas são encontradas?

Radiotelescopes Radiotelescopes (rotational (rotational lines)lines)

IR-Telescopes IR-Telescopes (vibrational lines)(vibrational lines)

Itapetinga, SPItapetinga, SP

VLAVLA

Hale-BoppHale-Bopp MurchinsonMurchinson

Gaseous Pillars – Eagle NebulaGaseous Pillars – Eagle Nebula Key hole NebulaKey hole Nebula

TitanTitan

Onde são encontradas as biomoléculas?

Galactic Habitability

Connecting Galaxy Formation to Biophilic Environments

• The galaxies are natural blocks (“cells”) from which the Universe is composed

• The stars occur in galaxies, and they are the responsible for the chemical evolution

• The galaxies have optimal levels of chemical abundances and radiation fields needed for the rise of the life

• The early evolution of galaxies are characterized by starbursts, in which dust and molecules are formed, leading to complex chemistry.

• The first, massive stars, harbored in protogalaxies, synthetize mainly CNO, thus organic chemistry is present in a Universe as young as z=30 at least

Galaxies and HabitabilityIntensive view

Galaxies as laboratories of complex chemistry

Example: dusty early spheroids(elliptical galaxies and bulges of spirals)

complex chemistry as revealed by PAH lines

• Spheroids in formation resemble dusty starburts• Large amounts of dust produced in 0.1-0.3 Gyr• Reprocessing of UV starlight into local FIR• Rest-frame FIR redshifted to submm/mm• Lines of PAHs (rest-frame MIR)

– Features at 3.3, 6.2, 7,7, 8.6 and 11.3 m due to C-H and C-C bounds

– Intensity of the features sets ages for the starburst in the 0.03-1 Gyr range

PAH Species in the Model

LINEAR

BIPHENILPERICONDENSATE

Spitzer Space Telescope

PAH WORLD

H

C

N

Recent detection of a PANH in the IRHudgins et al. ApJ, 2005

• 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.

Caffeine

From theRNA Worldto theAromatic World

Generalized PANH Species

Detecting PANHs through the 6.2 line

Detecting Water through the 6.2 line

Galaxies and HabitabilityExtensive view

Galactic Habitable Zone

Galactic Habitable Zone

Defined by PGHZ

• proportional to the star formation rate

• conditions for forming rock planets

• typical long evolutive biological times

• survival to violent galactic events (e.g. SNe)

HABITABLE ZONE (68% e 95%)

Lineweaver et al., Science, 303, 59 (2004)

Probability of Forming Rock Planets

• Probability of destroying Earths (parameter ZDE)

• Probability of producing Earths (parameter ZPE)

• Probability of harboring Earths (PHE=Pmetals)

•Highly Sensitive to the Metallicity* Z *Metals= for astrophysics every element heavier than He

Defined by Pmetals

Probability of Evolution over Biological Timescales

Defined by Pevol

• Darwin’s Theory requires long timescales

• Pevol depends on tevol

• For Earth tevol = 4 Gyr

• tevol could be shorter than 4 Gyr?

Probability of Survival to Galactic Violent Events

Defined by PSN

• Normalization to Earth?

• Pevol depends on past evens through tSN

• For Earth, tSN = tevol = 4 Gyr

• Again, tSN could be shorter than 4 Gyr

• Other Killers: GRBs, GMCs, AGNi

Extinction/Innovationof Life on Earth

How frequent are biophilic environments in galaxies?

Estimating through PGHZ

• comparing several galaxy types

• Spirals (disks) and Ellipticals (spheroids)

• Evaluated at several radii.

• Influence of AGNi ?

Star formation rate

Infall rate (thin disk)

Disk Model

Multi-Zone Double Infall Chemical Model

Galactic Habitable Zone

–Earth-Centered Case

Defined by PGHZ

• Pmetals: ZDE=0.3 ZDE=-1.0

• Pev: tev=4Gyr

• PSN: tSN=4Gyr PSN(2 Nsun)=0.5

•normalized to the Sun (r=8 kpc, t=13 Gyr)

Spheroid (Elliptical Galaxy)The Chemodynamical Model

• Multi-zone chemical evolution solver

+ hydrodynamical code

• Chemodynamical approach chemical evolution of the gas

+ dynamical state of the gas (inflow/outflow) star formation history even after galactic winds spatial variations in age and metallicity

• Bright Ellipical Galaxy

2 1011 Msun

Perspectives for Lifein an Extragalactic Setting

• Disks seem to be biophilic environments • In spheroids, conditions are too harsh or too

barren• In elliptical galaxies, the central regions could be

biophilic• Care should be taken against to be too earth-

centered• The inner regions of the Galaxy (between the solar

radius and 2 kpc) are biophilic

Planetary Habitability

Stellar habitable zone

R

Main assumptions: Surface H2O for ~ Gyear, geological activity, CO2-H2O-N2 atmosphere, B-field, climate stability, resistance to catastrophes for ~ Gyear

Reasons for habitability on Earth1) Liquid water allowed microbes to originate and evolve

2) Moon prevents against chaos in Earth´s rotation axis

3) Plate tectonics replenishes CO2 for life to persist

4) A magnetic field protects from solar wind

5) Evolution of the Atmosphere➔ Microbes made O

2, CH

4 CH

4 then O

2 dominated

➔ Ozone layer formed at ~ 2.3 Gy➔ Simple algae, fungi developed

➔ More O2 and animals at 0.6 Gy

➔ Modern humans at 2 My (1/3 of the O2 goes to the brain)

➔ Mankind returns CO2 and increases the greenhouse effect