The Search For Extraterrestrial Life

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