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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




...
Fermi paradox

                • Time for an intelligent species to colonize
                       galaxy: 106 years

   ...
Fermi paradox

                • Time for an intelligent species to colonize
                       galaxy: 106 years

   ...
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)




                               ...
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 brightne...
What have we learned from
              planet searches so far?




Friday, February 13, 2009
Only high metallicity
                        stars have planets
          FISCHER & VALENTI                              ...
Stars with planets are young.
             
 The Sun may be one of the oldest stars with planets
                         ...
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...
The Habitable Zone is the range of distances
              from a star which allow a planet to support life




Friday, Fe...
What are the minimal
                    conditions for life?
                • How hot?                  • How radioactiv...
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
...
Cryptoendolithic
                ecosystem inside rocks
                 Algae

       White lichen

     Black Lichen



...
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
   ...
Lifeless desert in Oceans
   • Centers of oceans
     have very little life.
   • Plenty of liquid
     water
   • Plenty ...
Lessons from terrestrial life
       • Life can exist with only a bare minimum of
         ingredients:
              – Li...
Old Habitable Zone Theory
       • If planet is too close to star, fries through
         runaway greenhouse effect
      ...
New Habitable Zone Theory
       • Many other factors besides distance from the Sun
         help determine planetary clim...
How many habitable planets will
                   actually be alive?
       • Basic ingredients to make life are common
 ...
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) detecte...
Basic ingredients of life
       • Organic molecules detected in interstellar
         space.
       • Water (Ice) detecte...
Organic Molecules in interstellar
                          space
       • Amino Acids
       • Nucleic Acids
       • Soo...
Given the right ingredients, how
            easy is it to make life?



                                    34


Friday, ...
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 man...
Conclusion from oldest life
       • Earth was not habitable until
         3.8 billion years ago.
              – Too man...
Conclusion from oldest life
       • Earth was not habitable until
         3.8 billion years ago.
              – Too man...
Conclusion from oldest life
       • Earth was not habitable until
         3.8 billion years ago.
              – Too man...
Conclusion from oldest life
       • Earth was not habitable until
         3.8 billion years ago.
              – Too man...
Searching for life in the
                            Solar System



                                                    ...
Friday, February 13, 2009
led
                               ce
                              n
                            Ca




Friday, February ...
Detection of life around other stars




                                             ned
                                ...
Biomarkers in atmosphere




Friday, February 13, 2009
Biomarkers in atmosphere
       • Earth’s atmosphere shows
         strong signals of two biogenic
         molecules
    ...
Biomarkers in atmosphere
       • Earth’s atmosphere shows
         strong signals of two biogenic
         molecules
    ...
Biomarkers in atmosphere
       • Earth’s atmosphere shows
         strong signals of two biogenic
         molecules
    ...
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.
              –...
Friday, February 13, 2009
Formation of Oxygen Atmosphere
       • Life begins to saturate
         atmosphere with
         Oxygen
       • Oxygen k...
Lessons from formation of life
       • Complex multicellular life did not evolve until
         recently.
              –...
Lessons from Mars
       • Planetary climates
         can change
       • Complex life (if it
         ever existed) like...
Answer to Fermi
                               Paradox?
                • Sun may be among the first stars to have
        ...
Intelligent life
       • No information how                • Search for Extraterrestrial
         common intelligent life...
The End




Friday, February 13, 2009
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Astrobiology: Life on other planets

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An introduction to astrobiology for a general audience

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Astrobiology: Life on other planets

  1. 1. Astrobiology Searching for life on other planets Friday, February 13, 2009
  2. 2. The Drake equation can be used to organize our thoughts Friday, February 13, 2009
  3. 3. The Drake equation can be used to organize our thoughts Friday, February 13, 2009
  4. 4. Fermi paradox Friday, February 13, 2009
  5. 5. Fermi paradox • Time for an intelligent species to colonize galaxy: 106 years Friday, February 13, 2009
  6. 6. Fermi paradox • Time for an intelligent species to colonize galaxy: 106 years • Age of the Galaxy: 1010 years Friday, February 13, 2009
  7. 7. 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
  8. 8. How many planets are there? Friday, February 13, 2009
  9. 9. We now have discovered many planets around other stars, but no Earth analogs (yet) Friday, February 13, 2009
  10. 10. We now have discovered many planets around other stars, but no Earth analogs (yet) nsing microle habitable? pulsar Friday, February 13, 2009
  11. 11. Future missions approved by NASA will probe ‘habitable zone’ Friday, February 13, 2009
  12. 12. Kepler Transit search (scheduled launch 2/2009) Friday, February 13, 2009
  13. 13. In a transit search, we see when a planet passes in front of its star Friday, February 13, 2009
  14. 14. Transit searches are a cheap way to hunt for planets Friday, February 13, 2009
  15. 15. 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
  16. 16. What have we learned from planet searches so far? Friday, February 13, 2009
  17. 17. 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
  18. 18. 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
  19. 19. What planets support life? Friday, February 13, 2009
  20. 20. What is life? Friday, February 13, 2009
  21. 21. What is life? Friday, February 13, 2009
  22. 22. Life as we know it Friday, February 13, 2009
  23. 23. 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
  24. 24. The Habitable Zone is the range of distances from a star which allow a planet to support life Friday, February 13, 2009
  25. 25. 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
  26. 26. Thermophiles thrive at 90ºC (190ºF) Friday, February 13, 2009
  27. 27. Endolithic life eat and breath rock two miles undeground Friday, February 13, 2009
  28. 28. Dry valleys of antarctica 3 inches annual precipitation -68ºC Dry 200 mph winds evaporate all moisture Friday, February 13, 2009
  29. 29. Cryptoendolithic ecosystem inside rocks Algae White lichen Black Lichen Friday, February 13, 2009
  30. 30. Bacteria living at bottoms of perpetually frozen lakes. Friday, February 13, 2009
  31. 31. Extreme life in Permafrost Friday, February 13, 2009
  32. 32. Atacama Desert dryest place on earth 2 mm decadal precipitation recent discoveries of life below 4 inches Friday, February 13, 2009
  33. 33. 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
  34. 34. 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
  35. 35. 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
  36. 36. 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
  37. 37. 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
  38. 38. Basic ingredients of life Friday, February 13, 2009
  39. 39. Basic ingredients of life • Organic molecules detected in interstellar space. Friday, February 13, 2009
  40. 40. Basic ingredients of life • Organic molecules detected in interstellar space. • Water (Ice) detected throughout galaxy, solar system. Friday, February 13, 2009
  41. 41. 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
  42. 42. Organic Molecules in interstellar space • Amino Acids • Nucleic Acids • Soot Friday, February 13, 2009
  43. 43. Given the right ingredients, how easy is it to make life? 34 Friday, February 13, 2009
  44. 44. Friday, February 13, 2009
  45. 45. Earliest Life • Bands of Carbon in ancient rock Friday, February 13, 2009
  46. 46. Conclusion from oldest life Friday, February 13, 2009
  47. 47. Conclusion from oldest life • Earth was not habitable until 3.8 billion years ago. – Too many impacts melted surface. Friday, February 13, 2009
  48. 48. 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
  49. 49. 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
  50. 50. 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
  51. 51. 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
  52. 52. Searching for life in the Solar System 38 Friday, February 13, 2009
  53. 53. Friday, February 13, 2009
  54. 54. led ce n Ca Friday, February 13, 2009
  55. 55. Detection of life around other stars ned tpo pos ly nite efi Ind Friday, February 13, 2009
  56. 56. Biomarkers in atmosphere Friday, February 13, 2009
  57. 57. 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
  58. 58. 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
  59. 59. 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
  60. 60. What planets support intelligent life? Friday, February 13, 2009
  61. 61. Simple life Friday, February 13, 2009
  62. 62. Complex Life Friday, February 13, 2009
  63. 63. 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
  64. 64. Friday, February 13, 2009
  65. 65. 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
  66. 66. 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
  67. 67. 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
  68. 68. 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
  69. 69. 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
  70. 70. The End Friday, February 13, 2009

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