1Alternative IdeasAlternative IdeasA different initial genetic substance + genetictakeovere.g. clay lifePanspermiaVarious versionsCreationism2Clay LifeSilicate Life? Early Genetic MaterialO = Si = O but O can make another bond instead great variety of mineralsLayers - clayAlso occasional impurity (Al, Mg, …)Can grow by adding dissolved materialTends to copy pattern of impurities in adjacentlayers reproduction?A.G. Cairns - SmithOOOOSiDefects - different impurity, … (mutations?)Sheets can separate - move - and then“reproduce”Advantages ProblemClay clearly present How to get toSimpler genetic structure life as we know itCrystal growth occurs naturally3Clay Life LifeClay life begins to synthesize, use “organic”[carbon] moleculesClays do have some catalytic activityGenetic takeoverorganics protein/RNA mechanismsClay discarded?Tests1. Surviving clay life - unlikely2. New clay life - maybe in some places3. Demonstrate in lab4Focus on EnergyG. WächtershäuserInorganic - organic connectionFeS2 (Iron pyrite)Attracts negatively charged moleculesSurface catalysis provides energy via formation fromFeS + H2SScene is hot sulfur vents on sea floorSome recent successes in simulationsAmino acids formed peptide bondsPanspermia• Life arose elsewhere and was delivered here– Original idea was bacterial spores– Hoyle and Wickramasinghe• Life originates on dust grains, comets, …– May be revived (meteorites from Mars)• Directed panspermia– Crick and Orgel (tongue in cheek)– Earth seeded by intelligent ET5Creationism• Traditional biblical literalism• Intelligent design– Seeks evidence of design in complexity– Current version of creationist movement– Hoyle and Wickramasinghe later ideas• Life designed by silicon chip• Where did the chip come from?• None of these are scientific theories– The key is whether they can be testedFrom “Scientific Creationism” by Henry MorrisBibleMatter created by God in the beginningEarth before the sun and starsOceans before the landLight before the sunAtmosphere between two hydrospheresLand plants, first life forms createdFruit trees before fishesBirds before insectsLand vegetation before the sun Birds before reptilesMan before woman (by creation)Man before rainCreation completedMan, the cause of struggle and deathUniformitarianismMatter existed in the beginningSun and stars before the earthLand before the oceansSun, earth’s first lightContiguous atmosphere and hydrosphereMarine organisms, first forms of lifeFishes before fruit treesInsects before birdsSun before land plantsReptiles before birdsWoman before man (by genetics)Rain before man“Creative” processes still continuingStruggle and death necessary antecedents of man6 Science (Logos)Provisional truthSkepticism essential(falsifiability)Method importantInterplay:Theory Experiment/ observationParadigmChemical Evolutionrelated? Myth (Mythos)Revealed truthunquestionedTwo strands inCreation Myths:Creator Spirit in “Western” Matter “Eastern”Creationism spontaneous generation self-organization of matterArtificial Life?• Polio virus constructed from “scratch” in 2002• Have they created life?• Viruses are parasites, but “protolife”?• Could we create free-living organism?• Far too complex for current abilities7Exotic Life Forms?Antidote to Earth Chauvinism1. Different organic molecules (e.g., PNA)Rebek’s variation self replicationpossibility of life based on other polymers2. Not based on CarbonSilicon (Si) instead of Carbon?(also 4 bonds)& more (135 ¥) more abundant on EarthNegatives:a. C - C bond 2 ¥ stronger than Si - Sib. Si - O stronger than Si - Sisilicates, not .. Si - Si - Si …c. C forms multiple bonds (e.g. C ≡ N)Si rarely diesd. C + O CO or CO2 (gas - further reacts)Si + O SiO2- silicate rocksfi Si unlikely to replace CSiO2(clay life)?83. Other SolventsEarth: Liquid water 273-373 KAlternatives: TfreezeTboilAmmonia NH3195 240Methyl Alcohol CH3OH 179 338Methane CH4 91 109Ethane C2H6 90 184Water is better solventAlso better for temperature regulationBut others could play a role in colder zonesextend CHZ?4. Non-chemical life?Disembodied intelligenceBlack cloud life?Other forcesStrong nuclear force? t ~ 10-15 sGravity?9Estimates for fl• Possible range is very large– Perhaps 10–6 (one in a million) to 1 (all)• Arguments for large value– Life part of overall evolution in complexity– Arises naturally from interplay of forcesEstimates for fl• Arguments for small value– May need more than liquid water• Large tides, so large moon• Dry land (for polymerization)– Life may be a fluke• A rare statistical event10Can we estimate fl from early origin of life?Very ancient microfossils (now disputed)fi Life arose as early as 3 ¥ 109 yr ago[soon after end of heavy bombardment]Lineweaver & Davis argued:Early origin fi fl> 0.33For suitable planets older than 1 ¥ 109 yrs.Statistics from one example!Others have disputed this
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