Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Steven Prinsen Dan Cipera Mat Remillard Mark Johnson What Is Life? The Search Within Our Solar System Searching Beyond the Solar System Probability of Life Broad definition • • “The period between birth and death” “The sum of all activities of a plant or an animal” “Activities” Respiration • Reproduction • Nutrition • Excretion • Locomotion • Growth • Reaction to stimuli • Quartz Lifelike Growth Nutrition Reproduce? Not Lifelike Movement Excretions External Stimuli www.howstuffworks.com/quartz-watch.htm • Fire – Lifelike • • • • • • • – Respiration Growth Movement Reproduction Eats Excretes Reacts to stimuli Not Lifelike • Evolving • Adaption to change www.funsci.com/fun3_en/fire/fire.htm Life Growth Reproduce Adapt Evolve http://www.hickerphoto.com/rain-forest-streams-9157-pictures.htm • 95% of Life – • Last 5% – • Calcium, Phosphorus, Chlorine, Sulfur, Potassium, Sodium, Magnesium, Iodine, Iron, and trace elements Most abundant universal elements – – • Hydrogen, Oxygen, Carbon, Nitrogen Hydrogen, Oxygen, Carbon, Nitrogen Helium, Neon Most abundant earth elements – Silicon, Iron, Magnesium, Oxygen The Search For Life In The Universe, Goldsmith and Owen • Carbon – – • Monomers – – – • Complex molecules Nitrogen and Oxygen Small molecules Compose polymers Amino Acids, sugars, fatty acids, nucleotides Polymers – – More complex molecules Proteins Laevorotatory (L) vs Dextrorotatory (D) Non living material is 50/50 L configuration Amino Acids D configuration Sugars, DNA, RNA Increases efficiency Amino Acids 20 used Astrobiology, November 10, 2008. 100 per protein 20100 possible combinations Meteorites L-amino acids 16% excess Astrobiology, November 10, 2008. Nucleotides Four types A, T, G, C Specify Amino Acids 16 combinations Sets of Three 64 combinations Redundancies Prevents mistakes http://yihongs-research.blogspot.com/2008/09/new-generationbusiness-demands-new-dna.html • Molecular level – DNA Mutation • Gamma Rays • Cosmic Rays • Mutagens – • Changes reproductive efficiency Energy – – From the Sun Photosynthesis Sunlight Steady energy Key to survival 3.5 billion years Photosynthesis Ensures a chance to survive http://photo.net/photodb/photo?photo_id=3666216 Formed by accretion Hydrogen Reducing Methane Ammonia Water Vapor Resembles Jupiter and Saturn Left quickly Volatile elements joined earth last H, C, N, O Life elements Comets http://www.williamsclass.com/EighthScience Work/Atmosphere/EarthsAtmosphere.htm Hydrogen bound to Oxygen UV breaks up Photodissociation Made new compounds Chem Reactions with crust Mildly Reducing CO CO2 N2 H2O H, H2 Mars, Venus Astrobiology, Monica Grady Water doesn’t imply life May be able to detect atmosphere data Transiting planets Nonequilibrium reaction byproducts Free Oxygen Photosynthesis Terrestrial Similarities M ≈ 1 Earth Mass Iron Core -> Magnetic Field Orbit The and Rotation 4 Most Vital Elements for Life Carbon, Liquid Hydrogen, Oxygen, Nitrogen Water! Europa Galileo Missions Slightly smaller than our moon Silicate Rock – Iron Core Atmosphere of Oxygen Smooth, icy surface Oceans Underneath? Extremophiles? Titan Cassini-Huygens Mission 50% Larger than our moon Surface of water ice and organic compounds Thick Atmosphere of Nitrogen Liquid Hydrocarbon Lakes (Ethane and Methane) But... -290 F (-179C) Mariner Probes No Plate Tectonics No Global Magnetic Field Atmospheric Pressure roughly 1% of Earth's No liquid water on surface … No multicellular organisms Viking Landers Search for bacteria-like organisms Soil showed C02 production when interacted with water No organic molecules detected Phoenix Lander (May 25 2008) Water-ice in Martian subsurface Small concentrations of salts Mars Reconnaissance Orbiter (November 20, 2008) Vast glaciers of ice Evidence of a previously “wet” Mars Planned Missions Mars Science Laboratory (2009) Maven (2013) Other Proposals Mars Sample Return Astrobiology Field Lab Deep-Drill Lander Idea is to Identify “Earth-like” planets- rocky worlds similar to our own Very difficultmost exoplanets we’ve found thus far are gas giants the size of Jupiter Planet’s gravity affects it’s parent star- causes slight variations in star’s radial velocity These variations are detectable by measuring Doppler shifts (i.e. a spectrograph measuring Doppler shifts in spectral lines from a star) Current instruments can detect ~1 m/sec shift; problem is, Earth-size planets induce ~0.1 m/sec shift Also, can only tell mass- not diameter/ composition/ atmosphere/ etc. HARPS 3.6 m telescope (www.eso.org) As planet transits in front of sun, dip in luminosity is recorded Technique can be used to determine diameter and mass, thus giving a density Orbit must lie in correct plane Period must be sufficiently short, or telescope must observe star continuously for a longer time www.space.com Best way to determine a planet’s chemical make-up (analyzing spectral lines) Fomalhault b was first exoplanet to be directly imaged visually - HST Problem: for most stars, luminosity from star far outshines reflection from planet Also, Earth’s atmosphere both narrows observable frequency ranges and causes blurring/seeing of visible light Fomalhault b www.spacetelescope.org Space-based telescopes (Hubble, Kepler, TPF) negate the atmosphere problem The light problem is much trickier (for example, at 10 pc, angular separation for 1 A.U. is 100 marcseconds) To block out the light from the star, a coronagraph is needed Possible designs for the Terrestrial Planet Finder satellites planetquest.jpl.nasa.gov Kepler Space Telescope www.seti-inst.edu Ratio of Sun’s Luminosity to light reflected from Earth -Lsun= 4e33 erg/sec -1 AU= 1.5e13 cm -Earth’s radius= 6.4e8 cm -Earth’s Albedo= 0.367 Flux from the sun to Earth: Fsun L 4 1033 6 2 1.4 10 erg/sec/cm 4ππ 2 4ππ(1. 1013 ) 2 “Luminosity” of Earth LEarth (rE2 )( Fsun ) 0.367(3.14)(6.4 108 ) 2 (1.4 106 ) 6.6 1023 erg / sec Ratio LEarth 6.6 10 23 1 LSun 4 10 33 1.7 1010 (About 1 in 20 Billion) Occulter: part of a coronagraph that physically blocks light from a star Problems: lower resolution, diffraction effects still obscure planet New Worlds Mission- use a distant occulter to block star’s light Geometry of occulter can be modified to “smooth out” diffraction rings Occulter can also be “apodized”- modified to help offset diffraction effects New Worlds Mission Concept www.planetquest.jpl.nasa.gov Chemical Composition- Water, Oxygen, Ozone, CO2 Can determine through spectral analysis “Red Edge”- Chlorophyll in plants reflects in infrared Changes in reflectivity If a star passes in front of a background star, the gravity of the foreground star causes microlensing The presence of a planet orbiting the foreground star affects the observable microlensing This effect can be observed even with planets at Earth’s scale Correct alignment is very rare, and only observable for a few days/weeks An equation postulated by Dr. Frank D. Drake in 1961. The Drake equation in it’s original form: Dr. Frank Drake N*= Total stars in galaxy fs = sun-like stars (fraction) fp = stars with planets (fraction) fi = planets with life (fraction) ne = life supportable planets fc = planets with intelligence (fraction) fl = life time of communicative civilization (fraction) Galaxy Factors Solar System Factors “Earth” Factors Wild Cards Galaxy Factors Type of galaxy Enough heavy elements Not small, irregular or elliptical Position in galaxy Not positioned in the halo, edge, or center Solar System Factors Stable planetary mass Giant planets allow for orbital stability Jupiter-like neighbor Absorbs comets and asteroids A Mars Possible life source Large Moon Stabilizes tilt Right Mass of star Right amount of ultraviolet released Long enough lifetime “Earth” Factors Distance from star Sufficient amount Habitat for complex life Liquid water near surface Enough heat for plate tectonics Able to support atmosphere and ocean Right composition and Planetary mass Solid/molten core pressure Carbon amount Enough for life but not enough for runaway greenhouse effect Oxygen Evolution Development of Tilt Mild seasons Atmospheric properties Adequate temperature No tidal lock Oceans’ size photosynthesis Biological evolution Complex plants and animals “Earth” Factors Giant impacts Plate tectonics Few giant impacts Land mass creation No major sterilizing Biotic diversity impacts Silicate thermostat Magnetic field Wild Cards Inertial interchange event Snowball Earth Cambrian explosion An equation suggested by Professor Peter Ward and Professor Donald Brownlee from their book “Rare Earth”: N*= Total stars in galaxy fc = planets with complex life (fraction) fp = stars with planets (fraction) fi = planets with life (fraction) fpm = metal-rich planets (fraction) fm= planets with large moon (fraction) ne = life supportable planets fj = Jupiter-sized planets (fraction) ng = stars in habitable zone fme = low number of mass destruction events (fraction) fl = life time of complex life (fraction) Drake Equation with Dr. Drake’s current estimation of intelligent life in our galaxy: Rare Earth Equation with our estimation of intelligent life in our galaxy: The Point: If any of these many variables approach zero, the total will be near zero! “I'll tell you one thing about the universe, though. The universe is a pretty big place. It's bigger than anything anyone has ever dreamed of before. So if it's just us... seems like an awful waste of space”. -Ellie Arroway, Contact “…And pray that there's intelligent life somewhere up in space, -'Cause there's buggerall down here on Earth”. -Monty Python and the Meaning of Life What Is Life? The Search Within Our Solar System Searching Beyond the Solar System Probability of Life Astrobiology, Monica Grady, The Natural History Museum, London, 2001 The Search For Life In The Universe, 2nd Edition, Goldsmith and Owen, Addison-Wesley Publishing Company, 1992 A Race To Find Alien Planets, Carlisle, Sky & Telescope, January 2009, p28. Circular Polarization and the Origin of Biomolecular Homochirality, Bailey, Bioastronomy, 1999 On the Origins of Biological Homochirality, Sandra Pizzarello, Astrobiology, November 10, 2008. www.nasa.gov Rare Earth, Ward, Brownlee, Springer Science, 2000 Titan: Earth in Deep Freeze, Barnes, Sky & Telescope, December 2008 Are We Alone, Imaging Extrasolar Earthlike Planets from Space, Presentation by Prof. N. Jeremy Kasdin David J. Des Marais et al. “The NASA Astrobiology Roadmap.” 9 Oct 2008. 19 Oct 2008