Life in the UniversePale Blue DotSlide 3Slide 4Slide 5Slide 6Clicker Question:Slide 8Slide 9The Drake Equation N = R*fpneflfifcLSlide 11N = R*fpneflfifcLSlide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Hello, Earth calling…Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50SETI: Search for Extraterrestrial IntelligenceThe End …Life in the UniverseIs there anybody out there? What might other forms of life look like? What about intelligent life? What do we mean by “living”? What do we mean by “intelligent”?Pale Blue DotEarth as seen from Voyager 1, when it was 6 billion km from home.View from Apollo 17What does the dominant life form look like?View from overhead (courtesy google Earth)7 tests for life1. Complex Organization2. Convert food to energy3. Reproduce4. Growth and Development5. Respond to stimuli6. Adapt to Environment7. Show individual variationWhat is Life?Intelligent Life:1. Ability to use tools2. Language3. Ability to learnNow Define Intelligent LifeClicker Question:Which land animal on Earth is or was the dominant species for 150 million years?A: man and other hominidsB: dogs and other caninesC: dinosaursD: insectsClicker Question:Which of the following is NOT necessarily a sign of intelligent life?A: ability to communicate (use language)B: ability to learnC: ability to reproduceD: ability to use toolsClicker Question:Are there other intelligent life forms in our Galaxy that we could communicate with?A: No, just 1 advanced civilization in the whole Milky WayB: Yes, a few perhaps 100 in the Milky WayC: Yes, many, 10000 in the Milky WayD: Yes, lots, 1 million in the Milky WayThe Drake EquationN = R*fpneflfifcLthe number of civilizations in the Galaxy that can communicate across stellar distancesThe Drake Equationnumber of technological, intelligent civilizations in the Milky Wayrate at which new stars are formed=xfraction of stars having planetary systemsxaverage number of habitable planets within those planetary systemsxfraction of those habitable planets on which life arisesxfraction of those life-bearing planets on which intelligence evolvesfraction of those planets with intelligent life that develop technological societyaverage lifetime of a technological civilizationxxEach term is less certain than the preceding one!N = R*fpneflfifcLthe rate at which suitable new stars are forming each year in the GalaxyThe Galaxy has ~400,000,000,000 stars, which are forming, living, and dying in billion year cycles- Stars are the fundamental platforms and energy sources for life…Location of SunN = R*fpneflfifcLStars being born…N = R*fpneflfifcLR* is pretty well known becauseastronomical technology is up to the task of measuring it…R* ~ 10 stars per yearN = R*fpneflfifcLthe fraction of suitable new starsaround which planets formN = R*fpneflfifcLAnother way to find planets…N = R*fpneflfifcLSpace-based Infrared InterferometeryDarwinVenus and Earth detection from 30 light years away!N = R*fpneflfifcLfp is becoming better known as we speak… long term Doppler programs and future space mission like TPF and Darwin will increase our knowledge.fp ~ 0.5N = R*fpneflfifcLthe number of planets residing in an ecosphere, the shell of lifeDirect energy: light from star•Proximity to star (too close, too far, just right)•Atmosphere of planet (climatic evolution)Indirect energy: localized•Solar wind + local magnetosphere•Geothermal (radioactive decay)•Central Planet (tidal forces on moons)Requires stability and flexibility for billions of yearsN = R*fpneflfifcLVenusToo close to the SunVenus suffers from a runawayGreenhouse effect, in whichlight energy from the star istrapped as heat by the atmosphere.N = R*fpneflfifcLMarsToo far from the SunMars suffers from a runawayIce Catastrophe, in whichlight energy from the star isreflected back into space.N = R*fpneflfifcLIn the zone …N = R*fpneflfifcLne probably is zero in some planetary systems and is a few to several in others (ours?). We need to know what ne is on average, its typical value.ne uncertain (~ 2?)N = R*fpneflfifcLthe fraction of ecosphere planets on which life arises Key Question: how readily does life arise?N = R*fpneflfifcL•All life (as we know it) is made of carbon based molecular chains•Only 30 complex molecules comprised of only five (5) basic elements•Urey-Miller experiment in 1953 showed that we could build amino acidsC = carbonH = hydrogenN = nitrogenO = oxygenP = phosphorousDNA moleculeN = R*fpneflfifcL•C, H, N, and O are among the five most abundant elements is the universe; (helium is 2nd to hydrogen)•The five elements of life are created in stars and supernovae explosions distributed them throughout the interstellar medium •Organic molecules, such as amino acids, are commonly found in interstellar, molecular gas clouds, and in comets and meteoritesN = R*fpneflfifcLComets, such as Halley, contain water ice and organic molecules, which are evaporated into interplanetary space•Building blocks of planets during planet formation epoch•Deposit water and organic molecules on planets•Can alter course of evolution if impacting life bearing planetN = R*fpneflfifcLJust how robust is life?• Life persists in a wide range of terrestrial environments- from the high desert to frozen ice tundra, from the tropics to the black depths of the oceans…Are there alternatives to photosynthesis?• Life in the ocean depths exploits geothermal energy and survives not on sunlight, but on bacteria that metabolizes sulfuric acid outgasing from thermal ventsLife can arise in a range of environments and can survive on a variety of primary energy sources.N = R*fpneflfifcLHow will we detect signs of life on extrasolar planets?Terrestrial Planet FinderSpectrum of an Earth-like planetozonecarbon dioxidewaterTerrestrial Planet Finder will take spectra of earth sized planets up to 30 light years away!Ozone, water, and carbon dioxide absorption features are indirect indicators of life processes (photosynthetic)N = R*fpneflfifcLfl , presently, can be guesstimated only by carefully studying our solar system, and in particular, Earth. fl ~ 0.1-1 (?)NOTE: fl is likely not vanishingly small, say 10-8 or soThat life is a “language” with a 30 molecule “alphabet” and is comprised of the five