Astrobiologie: De speurtocht naar leven in het universum

Astrobiologie: De speurtocht naar leven in het universum
Prof. Marco Spaans
Kapteyn Instituut, RUG
First stars
13.7 billion years
WMAP
CO detected at z=6.8
Joyce 2002
CURRENT SOLAR SYSTEM
Central star: SUN ­ contains 99 % of the total mass of the solar system
­ 9 major planets, which contain most of the angular momentum
Rocky terrestrial planets:
Mercury, Venus, Earth/Moon, Mars
­ Made up of metals and silicates
Jovian planets (gas giants):
Jupiter, Saturn, Uranus, Neptune
­ Predominantly made of 98 % H and He
All planets orbit the Sun in the Sun´s equatorial plane Pluto is an exception, Pluto´s orbit is eccentric and tilted 17.2 degrees
Vroeger was het zonnestelsel een grote wolk van gas en stof
Gravitationele ineenstorting wolk
Vorming van schijf
Vorming van planetesimalen uit stof;
Moeilijk om van 1 m → 1 km te gaan!!
Agglomeratie planetesimalen tot planeten
Vorming van zonnestelsel
Heavy bombardment phase
kg carbon/yr
(4­3.8 x 109 y)
Chyba & Sagan (1992)
EARLY EARTH
• Strong bombardment through comets over 700 mill. years
• Strong geological activity
• First evidence for Life: ~ 3.6 billion years ago PHYSICAL LIMITS FOR LIFE ON EARTH
Parameter Limiting Conditions Type of Organism
Water Liquid water required
Temperature ­2oC (31.8 F) minimum
50­80oC (122­176 F)
80­115oC (176­239 F)|
Psychrophiles
Thermophiles
Hyperthermophiles
Salinity
Halophiles
15­37.5 % NaCl
pH
0.7­4
Acidophiles
8­12.5 Akalophiles
Atmospheric
pressure up to 110 Mpa Barophiles
Extreme Life ….
Hydrothermal vents
Antarctica
Iron Spring Nymph Greek
Cyanidium caldarium (Rotalgen) bei pH~3.3 und 42 C
Norris Geyser Basin, Yellowstone Park
THE TREE OF LIFE
You are here!
 Zoek naar habitats and signaturen voor leven buiten de Aarde
Exploration of our Solar System and the search for extrasolar planetary systems
 Development of ground­and space based telescopes
space missions, laboratory simulations, design of
dedicated instrumentation and robotic tools
J. Garry 2003
In the search of processes leading to life, Mars, Europa and Titan are special targets for Solar System exploration
 Mars may harbour extinct or extant life within its subsurface
 Europa may hide an ocean below the thick ice crust  Titan reveals an active carbon and nitrogen chemistry in its dense atmosphere
EUROPA ­ Water and Life ?
Europa fulfills the necessary criteria for life to develop  The interaction between Jupiter and Europa is a source
of internal energy and possible liquid water: tidal heating  Possible presence of organic molecules Duidelijke structuren, recent…
Thermal structure ­ EUROPA
Surface ­ 100 K, 1mm amorphous, below crystalline
Ice, solid shell overlying the warmer liquid below 0­4C Bottom ice shell T defined by melting point of ice at given pressure (thickness), salinity If pressure at base shell is not too high (< 30 MPa) and the ocean has a salinity <30 gm salts per kg water, than water at the base shell may be warm and a boundary layer is formed – heat transport by conduction!
15 km
Stratosphere cool/buoyant, stably stratified water, freezing point
100 km
Deep convecting liquid water ocean
well­stirred, rather homogenous,
thermal fluctuation of 5 x 10­4 Hot boundary layer (10cm)
rock
Basal heat flux Qb = 8­10 mW/m2
Melosh et al. 2004 JIMO
The Jupiter Icy Moons Orbiter is an ambitious proposed mission to orbit three planet­sized moons of Jupiter  Callisto
 Ganymede  Europa The mission would launch in 2013­2015
The surface of Saturn’s moon TITAN
 Bright zones: Ice or rock ?
 Dark zones: Oceans made of liquid hydrocarbons ?
Voyager 1: Ethane­methane oceans on Titan’s surface ?
CH4 in atmosphere is destroyed irreversibly
Between 100­600 meters of liquid C2H6 has been deposited over time—and could be one component of a ternary methane­ethane­nitrogen ocean—if photolytic destruction of CH4 has gone on in steady­state.
Such an ocean would be both the source (methane) and sink (ethane) of the methane photochemistry in Titan’s stratosphere Titan’s surface, hidden from the cameras of Voyagers 1 and 2, should be covered to a large extent by liquid hydrocarbons
Lunine 2003
CASSINI­HUYGENS visited Titan
6 instruments on board measure the physical and chemical conditions of Titan’s atmosphere
Reliëf, meren en wolken
Een vulkaan!
Koolstofketens in de atmosfeer van Titan…actieve chemie
Volgende keer: Detectie van exoplaneten