Astrobiology: Life on other planets
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Astrobiology: Life on other planets

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An introduction to astrobiology for a general audience

An introduction to astrobiology for a general audience

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Astrobiology: Life on other planets Astrobiology: Life on other planets Presentation Transcript

  • Astrobiology Searching for life on other planets Friday, February 13, 2009
  • The Drake equation can be used to organize our thoughts Friday, February 13, 2009
  • The Drake equation can be used to organize our thoughts Friday, February 13, 2009
  • Fermi paradox Friday, February 13, 2009
  • Fermi paradox • Time for an intelligent species to colonize galaxy: 106 years Friday, February 13, 2009
  • Fermi paradox • Time for an intelligent species to colonize galaxy: 106 years • Age of the Galaxy: 1010 years Friday, February 13, 2009
  • Fermi paradox • Time for an intelligent species to colonize galaxy: 106 years • Age of the Galaxy: 1010 years • where are they? Friday, February 13, 2009
  • How many planets are there? Friday, February 13, 2009
  • We now have discovered many planets around other stars, but no Earth analogs (yet) Friday, February 13, 2009
  • We now have discovered many planets around other stars, but no Earth analogs (yet) nsing microle habitable? pulsar Friday, February 13, 2009
  • Future missions approved by NASA will probe ‘habitable zone’ Friday, February 13, 2009
  • Kepler Transit search (scheduled launch 2/2009) Friday, February 13, 2009
  • In a transit search, we see when a planet passes in front of its star Friday, February 13, 2009
  • Transit searches are a cheap way to hunt for planets Friday, February 13, 2009
  • USING PHOTOMETRY TO DETECT EARTH-SIZE PLANETS The relative change in brightness (ΔL/L) is equal to the relative areas • (Aplanet/Astar) Jupiter: Earth or Venus 1% area of the Sun (1/100) 0.01% area of the Sun (1/10,000) Small planets need ultra-precise photometry. Must be done with wide- field CCD imager in space. Friday, February 13, 2009
  • What have we learned from planet searches so far? Friday, February 13, 2009
  • Only high metallicity stars have planets FISCHER & VALENTI Vol. 622 lity /Star tirety sical ance 0.3 × Solar 3 × Solar 03). In addition, a Fig. 5.—Same results as Fig. 4, but divided into 0.1 dex metallicity bins. The s been underway increasing trend in the fraction of stars with planets as a function of metallicity is 004). No planets well fitted with a power law, yielding the probability that an FGK-type star has a gas giant planet: P( planet) ¼ 0:03½(NFe =NH )=(NFe =NH ) Š2:0 . veys, suggesting nets with orbital ikely lower than) Friday, February 13, 2009
  • Stars with planets are young. The Sun may be one of the oldest stars with planets – 37 – s net pla rs ith sta rs w cal l lo Sta Al Friday, February 13, 2009
  • What planets support life? Friday, February 13, 2009
  • What is life? Friday, February 13, 2009
  • What is life? Friday, February 13, 2009
  • Life as we know it Friday, February 13, 2009
  • What planets support life? What kinds of planets can support life? What fraction of planets that can support life do support life? Friday, February 13, 2009
  • The Habitable Zone is the range of distances from a star which allow a planet to support life Friday, February 13, 2009
  • What are the minimal conditions for life? • How hot? • How radioactive? • How cold? • How poisonous? • How dry? • How much pressure? • How acid? • How barren? • How salty? Organisms that push these limits are called extremophiles Friday, February 13, 2009
  • Thermophiles thrive at 90ºC (190ºF) Friday, February 13, 2009
  • Endolithic life eat and breath rock two miles undeground Friday, February 13, 2009
  • Dry valleys of antarctica 3 inches annual precipitation -68ºC Dry 200 mph winds evaporate all moisture Friday, February 13, 2009
  • Cryptoendolithic ecosystem inside rocks Algae White lichen Black Lichen Friday, February 13, 2009
  • Bacteria living at bottoms of perpetually frozen lakes. Friday, February 13, 2009
  • Extreme life in Permafrost Friday, February 13, 2009
  • Atacama Desert dryest place on earth 2 mm decadal precipitation recent discoveries of life below 4 inches Friday, February 13, 2009
  • Lifeless desert in Oceans • Centers of oceans have very little life. • Plenty of liquid water • Plenty of sunlight energy • Missing some key chemicals – Phosphorus Friday, February 13, 2009
  • Lessons from terrestrial life • Life can exist with only a bare minimum of ingredients: – Liquid Water – Some energy source • Sunlight, Rocks, Geothermal energy – Basic chemical ingredients • Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus Friday, February 13, 2009
  • Old Habitable Zone Theory • If planet is too close to star, fries through runaway greenhouse effect • If planet is too far from star, freezes, can’t support life. Friday, February 13, 2009
  • New Habitable Zone Theory • Many other factors besides distance from the Sun help determine planetary climate – Greenhouse effect – Plate Tectonics – Impacts (Early Earth atmosphere stripped) – Tidal Heating (Io, Europa) • Liquid water can be found in a variety of unlikely environments – Europa, Callisto, Ganymede – Early Mars very wet, present Mars dry? Friday, February 13, 2009
  • How many habitable planets will actually be alive? • Basic ingredients to make life are common throughout the cosmos • Look at History of Life on Earth • Life began shortly after Earth cooled • Suggests that Life is easy to make. Friday, February 13, 2009
  • Basic ingredients of life Friday, February 13, 2009
  • Basic ingredients of life • Organic molecules detected in interstellar space. Friday, February 13, 2009
  • Basic ingredients of life • Organic molecules detected in interstellar space. • Water (Ice) detected throughout galaxy, solar system. Friday, February 13, 2009
  • Basic ingredients of life • Organic molecules detected in interstellar space. • Water (Ice) detected throughout galaxy, solar system. • The basic chemical ingredients of life are common throughout the galaxy. Friday, February 13, 2009
  • Organic Molecules in interstellar space • Amino Acids • Nucleic Acids • Soot Friday, February 13, 2009
  • Given the right ingredients, how easy is it to make life? 34 Friday, February 13, 2009
  • Friday, February 13, 2009
  • Earliest Life • Bands of Carbon in ancient rock Friday, February 13, 2009
  • Conclusion from oldest life Friday, February 13, 2009
  • Conclusion from oldest life • Earth was not habitable until 3.8 billion years ago. – Too many impacts melted surface. Friday, February 13, 2009
  • Conclusion from oldest life • Earth was not habitable until 3.8 billion years ago. – Too many impacts melted surface. • 3.8 billion years ago, many fewer impacts. – Earth became inhabitable. Friday, February 13, 2009
  • Conclusion from oldest life • Earth was not habitable until 3.8 billion years ago. – Too many impacts melted surface. • 3.8 billion years ago, many fewer impacts. – Earth became inhabitable. • Oldest life on Earth 3.8 billion years old. Friday, February 13, 2009
  • Conclusion from oldest life • Earth was not habitable until 3.8 billion years ago. – Too many impacts melted surface. • 3.8 billion years ago, many fewer impacts. – Earth became inhabitable. • Oldest life on Earth 3.8 billion years old. • Life formed on Earth as soon as Earth could support life. Friday, February 13, 2009
  • Conclusion from oldest life • Earth was not habitable until 3.8 billion years ago. – Too many impacts melted surface. • 3.8 billion years ago, many fewer impacts. – Earth became inhabitable. • Oldest life on Earth 3.8 billion years old. • Life formed on Earth as soon as Earth could support life. • Life is easy to form? Friday, February 13, 2009
  • Searching for life in the Solar System 38 Friday, February 13, 2009
  • Friday, February 13, 2009
  • led ce n Ca Friday, February 13, 2009
  • Detection of life around other stars ned tpo pos ly nite efi Ind Friday, February 13, 2009
  • Biomarkers in atmosphere Friday, February 13, 2009
  • Biomarkers in atmosphere • Earth’s atmosphere shows strong signals of two biogenic molecules – Oxygen • Produced by plants – Methane • Produced by Cows Friday, February 13, 2009
  • Biomarkers in atmosphere • Earth’s atmosphere shows strong signals of two biogenic molecules – Oxygen • Produced by plants – Methane • Produced by Cows • Normally, methane burns in Oxygen – Natural Gas Friday, February 13, 2009
  • Biomarkers in atmosphere • Earth’s atmosphere shows strong signals of two biogenic molecules – Oxygen • Produced by plants – Methane • Produced by Cows • Normally, methane burns in Oxygen – Natural Gas • Two can only exist in combination because both being produced by life. Friday, February 13, 2009
  • What planets support intelligent life? Friday, February 13, 2009
  • Simple life Friday, February 13, 2009
  • Complex Life Friday, February 13, 2009
  • Lessons from Extremophiles • Complex life on Earth restricted to narrow range of habitats. – Not in Antarctica, too cold, dry – Not inside rocks, nothing to eat, breath – Not inside geothermal vents, too hot – Not in clouds, too heavy – Not in driest deserts, too dry Friday, February 13, 2009
  • Friday, February 13, 2009
  • Formation of Oxygen Atmosphere • Life begins to saturate atmosphere with Oxygen • Oxygen kills off life • Oxygen combines with rock • Life comes back, makes more oxygen • Oxygen kills off life • Process continued for 800 million years. Friday, February 13, 2009
  • Lessons from formation of life • Complex multicellular life did not evolve until recently. – Cambrian Explosion 600 Mya. • Complex life could not have evolved without Oxygen atmosphere. • Complex life more fragile than simple life. • Complex life difficult to evolve. Friday, February 13, 2009
  • Lessons from Mars • Planetary climates can change • Complex life (if it ever existed) likely wiped out today. • Simple life could have survived. Friday, February 13, 2009
  • Answer to Fermi Paradox? • Sun may be among the first stars to have planets • Life may be common • Complex life may be rare • Complex life may take a long time to form • We may be alone? Friday, February 13, 2009
  • Intelligent life • No information how • Search for Extraterrestrial common intelligent life is. Intelligence: SETI – Cannot be federally funded – Took most of history of by congressional mandate earth to evolve an earthworm. – Now part of NASA’s Astrobiology Institute • Definition of Intelligent life: – Just another means to Ability to operate radio search for life transmitters – Privately Funded SETI • Search for intelligent life institute by searching for radio transmission Friday, February 13, 2009
  • The End Friday, February 13, 2009