Aula 8

Sigam a Água -1

FOLLOW THE LIFE• Solvent • Biogenic elements• Source of Free Energy

searches for life within our solar system commonly retreat from a search for life to a search for “life as we know it,” meaning life based on liquid water, a suite of so-called “biogenic” elements (most famously carbon), and a usable source of free energy.

(Chyba & Hand, 2005, p. 34)

Six “Major Biogenic Elements”:

Carbon, Hydrogen, Oxygen, Nytrogen, Sulfur,

Phosphorous (CHON + S + P)

Five “Minor Biogenic Elements”:

Sodium, Potassium, Magnesium, Calcium, Chlorine

FOLLOW THE LIFE

• Follow the water• Follow the carbon• Follow the nitrogen• Follow the energy• Follow the entropy• Follow the information

Astrônomos descobrem planeta que

pode ser habitável Folha Online 24/04/2007 - 22h44

Astrônomos encontraram um planeta fora do nosso Sistema Solar que é po-tencialmente habitável, com temperaturas parecidas com as da Terra. A des-coberta foi considerada um grande passo na procura por vida extraterrestre.

O planeta tem o tamanho certo, pode ter água em forma líquida e, em termos de Universo, está relativamente perto, a cerca de 20,5 anos-luz da Terra. Ele gira em torno de uma anã vermelha --uma estrela muito menor, menos luminosa e mais fria que o nosso Sol-- chamada de Gliese 581.

O novo planeta é cinco vezes mais pesado que a Terra. Não se sabe ainda se ele é rochoso como a Terra ou se é uma esfera de gelo, com água líquida na superfície. Se for rochoso, que é o que a teoria prevalecente propõe, tem um diâmetro cerca de 1,5

vez maior que o do nosso planeta. Se for uma esfera de gelo, seria maior ainda.

O planeta, batizado de Gliese 581c, foi descoberto pelo telescópio do Observatório Europeu do Sul (ESO) em La Silla, no Chile.Sistema planetário de Gliese 581

Instrumentos utilizados da descoberta de Gliese 581c

Telescópio de 3,6m do ESO, em La Silla, Chile, a 2400m de altitude

Equipe descobridora de Gliese 581c

Uma equipe de onze astrônomos da Suíça, França, e Portugal.

Esta equipe faz parte do grupo liderado por Michel Mayor, do Observatório de Genebra, na Suíça, responsável pela descoberta de 89 exoplanetas (até 4/6/2007)

Há mais de 680 exoplanetas descobertos até hoje

Michel Mayor

Detection of Planets-Radial Velocity Method

Detection of Planets-Transit Method

130,000 observed stars, ~150 new telluric planets

Blue Moon em torno de um Jupiter Quente

O Estranho Sistema Solar de Gliese 581

Planeta Massa “Ano” Distância

Gliese 581b 15 MTerra5,4 dias 6 milhões km

Gliese 581c 5 MTerra13 dias 11 milhões km

Gliese 581d 15 MTerra84 dias 38 milhões km

Distância “certa” para água líquida (temperatura= 0-40 C)

Gliese 581c – um mundo aquático?

Um planeta de classe Aurélia?

Um lado, dia para sempre

Outro lado, noite eterna

Por que Gliese 581c seria habitável?

R

Água Líquida ! Zona Habitável

A própria Terra é um “Planeta Água”A própria Terra é um “Planeta Água”

Europa – Um Oceano Subterrâneo

18

19NUPESC Ago 2012 19

A água é essencial para a vidacomo conhecemos

H2O

A água também pode ser essencial para a vida em outros pontos do

UniversoAfinal, há água por toda parte no

UniversoH2O = Hidrogênio + Oxigênio

Hidrogênio é o elemento mais abundante do Universo e o mais simples (só um próton)

Oxigênio (seis prótons e seis nêutrons) é o segundo elemento quimicamente ativo mais abundante

Hélio (dois prótons e dois nêutrons) é o segundo elemento mais abundante mas não é quimicamente ativo

Água

Principal componente dos cometas e dos seres vivos

Assim, o Oxigênio e o Hidrogênio são os elementos principais do Universo e dos seres vivos terrestres

Logo atrás vem o Carbono e o Nitrogênio.

DNA

H O C N + P

Relative abundances of chemical elements

Relative abundances of chemical elements (O=100)The abundances are in number (decreasing order)Sources: Lehninger 2000 (human body and Earth crust abundances); Asplind, Grevesse & Sauval 2004 (C, N, and O are solar

photospheric values; the other elements are solar system meteoritic values)

Human Body Earth Crust Cosmic

H 247 O 100 H 21 900

O 100 Si 59.6 O 100

C 37.3 Al 16.8 C 53.7

N 5.49 Fe 9.6 N 13.2

Ca 1.22 Ca 7.5 Mg 7.41

P 0.86 Na 5.3 Si 7.10

Cl 0.31 K 5.3 Fe 6.17

K 0.24 Mg 4.7 S 3.16

S 0.20 Ti 1.1 Al 0.58

Na 0.12 H 0.4 Ca 0.43

Mg 0.04 C 0.4 Na 0.41

Liquid Water

H20 is the combination of the two most abundant chemical elements in the Universe

H20 is the most abundant tri-atomic molecule in the Universe (but, requires stars to form O)

liquid H20 is much less common (needs a narrow range of pressure and temperatures)

liquid H20 requires planetary environmentshighest boiling temp= 650 K (high pressures)

History of the Complexity in the Universe

10-43 s 1. The space is born (4 extended dimensions)

10-33 s 2. The matter is born (quarks & leptons)

10-4 s 3. Baryons are born (quark confinements)1 minute 4. Nuclei are born (4He 2H 3He 7Li)300.000 yr 5. Atoms are born (H recombination)300 Myr 6. Heavy elements are born (C, O…) 7. Heteromolecules are born (OH, CO,

H2O…)~10 Gyr 8. Life is born ? (: at least 3.5 Gyr

ago)

Thermal History of the Universe

Transitions in the universe as the temperature decreases. Structures which freeze out as the universe cools include, matter, protons and neutrons, nuclei, atoms and molecules.

COSMIC BLACK BODY RADIATION(“3 degree K Radiation”)

Hot Ancestors and their Cool Descendants:Maximum Growth Temperatures

Phylogenetic tree of life based on 16S rRNA sequences (Pace 1997). Maximal growth temperatures have been used to color-code the branches

Re-setting the Phylogenetic Thermometer

Detecting Water in the Universe through the 6.2 line

HAC = Hydrogenated Amorphous Carbons

Water: Pros & ConsIt is easily done: it is a tri-atomic molecule and H and O

are the first and third most abundant elements in the universe.

It remains in liquid form for a relatively large temperature range (0 – 100ºC); these limits could be extended under pressure and by the presence of dissolved salts.

This temperature range include temperatures high enough for chemical reactions to proceed at a relatively rapid pace, but not so high that collisions destroy important, large and fragile molecules.

Water: Pros & ConsWater is a polar solvent so that it can discriminate

between polar and non-polar molecules. Chemical discrimination results on the formation of mixed phases such as membranes, microenvironments and compartmentalization.

Water has a very large heat of vaporization and a large heat of vaporization. This means that the temperatures of in solution is stabilized by the thermal properties of water as a solvent.

Its relatively high viscosity protects living organisms from strong dynamical instabilities.

Water: Pros & Cons

• The surface tension of water, twice that of ammonia and three times that of alcohol, exceeds the surface tension of any other liquid known.

• Its ice is less dense than that of water so that ice floats. Having a frozen ice cap protects life below the ice and prevents freezing throughout all the bulk of the liquid. (eg. EUROPA)

• It is rather corrosive and reactive.• It can hamper protein and nucleic acid

concentrations.• Its ice is less dense than that of water so that ice

floats. The high reflectivity of water ice could lead to thermal negative runaway conductive to global glaciations, that could turn into killing events.

Water: Pros & Cons

• The surface tension of water, twice that of ammonia and three times that of alcohol, exceeds the surface tension of any other liquid known.

• Its ice is less dense than that of water so that ice floats. Having a frozen ice cap protects life below the ice and prevents freezing throughout all the bulk of the liquid. (eg. EUROPA)

• It is rather corrosive and reactive.• It can hamper protein and nucleic acid

concentrations.• Its ice is less dense than that of water so that ice

floats. The high reflectivity of water ice could lead to thermal negative runaway conductive to global glaciations, that could turn into killing events.

Phase Diagram for Water

Triple Point273.16 K, 611.73 Pa

Critical Point647 K, 22.064 MPa

ALTERNATIVE CHEMISTRIES

FOR LIFE?

Melting and boiling point of possible solvents for life

Solvent Melting Point (o C) Boiling point (o C) Temperature range for liquid*

H2O 0 100 100

NH3-78 -33 45

CH4-182 -164 18

C2H2-183 -89 94

CH3OH -94 65 155

Water-based oceans

Other liquid possibilities

OUR SOLAR SYSTEM´S LIQUID POSSIBILITIES

water/ammonia (surfa

ce lakes)

water/ammonia (subsurfa

ce)

methane/ethane

(surface lakes)

nitrogen (surfa

ce)

nitrogen (subsurfa

ce)

O SISTEMA SOLARÉ ÚMIDO

SOL

MARTE

Água em Marte hoje•A baixa pressão atmosférica impede água liquída na superfície

Water on Mars

Water on Mars

Water on Mars

Water droplets collected on NASA’s Phoenix lander

Água líquida em Marte hoje?

• Ponto Triplo da água: (T,p)=(271.16 K, 611.73 Pa)• Pressão média em Marte: T= 600 Pa~6 mili atm• Pressão míxima: 30 Pa (Olympus Mons)• Pressão máxima: 1150 Pa (Hellas Planitia)

Mars

Europa (lua de Jupiter)

Criptoendoliths

Thermophile bacteria

Hidrotermal vents

Hot geisers and volcans

ExtremófilosAntarctica

•Temperatura: -15° C < T < 230° C•0.06 < pH < 12.8•0 < Pressão < 1200 atm•Seu metabolismo pode dispensar o oxigênio•20-40 milhões de anos de dormência•2 ½ anos no espaço, a –250 C, sem nutrientes,

água and expostos a radiação (Strep. Mitis)

Kuhn

Origem Cometária da Água na Terra

Comets, Astronomy & Astrobiology

Comets are the key to understanding the Solar Nebula & its evolution.

Comets could serve as probes of chemical processes occurring in the midplanes of astronomical disks

Comets may have provided key organic nutrients required to jump start life on Earth.

•

When comets are near the Sun and active, comets have several distinct parts:

nucleus: relatively solid and stable, mostly ice and gas with a small amount of dust and other solids

coma: dense cloud of water, carbon dioxide and other neutral gases sublimed from the nucleus hydrogen cloud: huge (millions of km in diameter) but very sparse envelope of neutral hydrogen

dust tail: up to 10 million km long composed of smoke-sized dust particles driven off the nucleus by escaping gases; this is the most prominent part of a comet to the unaided eye

ion tail: as much as several hundred million km long composed of plasma interactions with the solar wind

Major Comet Structures

COMA

ION TAIL

HI CLOUD

NUCLEUS

THE COMA

Molecules are liberated from the nucleus by solar heating and sublimation

Molecules are destroyed by photodissociation & photoionization

H2O + h H + OHOH + h H + O

H2O + h H2O+ + e-

Nucleus molecules are referred to as the “parent molecules”

The fragments produced by the absorption of a photon are called “daughters”

Chemical Composition of Comets

Bockelee-Morvan, Crovisier, Mumma, and Weaver (Comets II, 2003)

Abundances (%, relative to water)

(The grey bar indicates the range measured to date)