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The Search For Extraterrestrial Life

The Search For Extraterrestrial Life. 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. What is life?. Here on Earth. Broad definition “The period between birth and death”

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The Search For Extraterrestrial Life

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  1. The Search For Extraterrestrial Life Steven Prinsen Dan Cipera Mat Remillard Mark Johnson

  2. What Is Life? • The Search Within Our Solar System • Searching Beyond the Solar System • Probability of Life

  3. What is life?

  4. Here on Earth • 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

  5. Problems • Quartz • Lifelike • Growth • Nutrition • Reproduce? • Not Lifelike • Movement • Excretions • External Stimuli www.howstuffworks.com/quartz-watch.htm

  6. Problems • 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

  7. New Definition • Life • Growth • Reproduce • Adapt • Evolve http://www.hickerphoto.com/rain-forest-streams-9157-pictures.htm

  8. Composition of Life • 95% of Life • Hydrogen, Oxygen, Carbon, Nitrogen • Last 5% • Calcium, Phosphorus, Chlorine, Sulfur, Potassium, Sodium, Magnesium, Iodine, Iron, and trace elements • Most abundant universal elements • Hydrogen, Oxygen, Carbon, Nitrogen • Helium, Neon • Most abundant earth elements • Silicon, Iron, Magnesium, Oxygen

  9. The Search For Life In The Universe, Goldsmith and Owen

  10. Composition of Life • Carbon • Complex molecules • Nitrogen and Oxygen • Monomers • Small molecules • Compose polymers • Amino Acids, sugars, fatty acids, nucleotides • Polymers • More complex molecules • Proteins

  11. Monomers • 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 • 100 per protein • 20100 possible combinations Astrobiology, November 10, 2008.

  12. Monomers • Meteorites • L-amino acids 16% excess Astrobiology, November 10, 2008.

  13. DNA • 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-generation-business-demands-new-dna.html

  14. Progression of Life • Molecular level • DNA Mutation • Gamma Rays • Cosmic Rays • Mutagens • Changes reproductive efficiency • Energy • From the Sun • Photosynthesis

  15. 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

  16. Atmosphere • 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/EighthScienceWork/Atmosphere/EarthsAtmosphere.htm

  17. Atmosphere • 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

  18. Astrobiology, Monica Grady

  19. Conclusions • Water doesn’t imply life • May be able to detect atmosphere data • Transiting planets • Nonequilibrium reaction byproducts • Free Oxygen • Photosynthesis

  20. Terrestrial Similarities M ≈ 1 Earth Mass Iron Core -> Magnetic Field Orbit and Rotation The 4 Most Vital Elements for Life Carbon, Hydrogen, Oxygen, Nitrogen Liquid Water! The Search in Our Solar System

  21. Jupiter's Icy Moons • Europa • Galileo Missions • Slightly smaller than our moon • Silicate Rock – Iron Core • Atmosphere of Oxygen • Smooth, icy surface • Oceans Underneath? Extremophiles?

  22. Saturn's Icy Moons • 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)

  23. Mars Missions • Mariner Probes • No Plate Tectonics • No Global Magnetic Field • Atmospheric Pressure roughly 1% of Earth's • No liquid water on surface • … No multicellular organisms

  24. Mars Missions • Viking Landers • Search for bacteria-like organisms • Soil showed C02 production when interacted with water • No organic molecules detected

  25. Mars Missions 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

  26. Future Mars Missions Planned Missions • Mars Science Laboratory (2009) • Maven (2013) Other Proposals • Mars Sample Return • Astrobiology Field Lab • Deep-Drill Lander

  27. Looking for Life Beyond the Solar System • Idea is to Identify “Earth-like” planets- rocky worlds similar to our own • Very difficult- most exoplanets we’ve found thus far are gas giants the size of Jupiter

  28. Radial Velocity Technique • 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)

  29. Transit Technique • 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

  30. Direct Imaging • 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

  31. Solutions • 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

  32. Kepler Space Telescope www.seti-inst.edu Possible designs for the Terrestrial Planet Finder satellites planetquest.jpl.nasa.gov

  33. To give an idea…. • 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: “Luminosity” of Earth Ratio (About 1 in 20 Billion)

  34. More on Direct Imaging • 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

  35. Direct Imaging- what to look for • Chemical Composition- Water, Oxygen, Ozone, CO2 • Can determine through spectral analysis • “Red Edge”- Chlorophyll in plants reflects in infrared • Changes in reflectivity

  36. Gravitational Microlensing • 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

  37. Probability of Life

  38. Drake Equation An equation postulated by Dr. Frank D. Drake in 1961. The Drake equation in it’s original form: 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) Dr. Frank Drake

  39. Rare Earth Factors • Galaxy Factors • Solar System Factors • “Earth” Factors • Wild Cards

  40. Rare Earth Factors • Galaxy Factors • Type of galaxy • Enough heavy elements • Not small, irregular or elliptical • Position in galaxy • Not positioned in the halo, edge, or center

  41. Rare Earth Factors • 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

  42. Rare Earth Factors • “Earth” Factors • Distance from star • Habitat for complex life • Liquid water near surface • No tidal lock • Planetary mass • Solid/molten core • Enough heat for plate tectonics • Able to support atmosphere and ocean • Tilt • Mild seasons • Oceans’ size • Sufficient amount • Atmospheric properties • Adequate temperature • Right composition and pressure • Carbon amount • Enough for life but not enough for runaway greenhouse effect • Oxygen Evolution • Development of photosynthesis • Biological evolution • Complex plants and animals

  43. Rare Earth Factors • “Earth” Factors • Giant impacts • Few giant impacts • No major sterilizing impacts • Wild Cards • Inertial interchange event • Snowball Earth • Cambrian explosion • Plate tectonics • Land mass creation • Biotic diversity • Silicate thermostat • Magnetic field

  44. Rare Earth Equation 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)

  45. Equation Sample Calculations 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!

  46. Two last Thoughts • “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 bugger-all down here on Earth”. -Monty Python and the Meaning of Life

  47. Conclusion • What Is Life? • The Search Within Our Solar System • Searching Beyond the Solar System • Probability of Life

  48. Questions?

  49. References • 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 BiomolecularHomochirality, 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

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