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Searching for Life Beyond The Solar System

Searching for Life Beyond The Solar System. Dr. Victoria Meadows NASA Astrobiology Institute Spitzer Science Center/California Institute of Technology. Life Beyond Our Solar System.

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Searching for Life Beyond The Solar System

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  1. Searching for Life Beyond The Solar System Dr. Victoria Meadows NASA Astrobiology Institute Spitzer Science Center/California Institute of Technology

  2. Life Beyond Our Solar System “There are countless suns and countless earths all rotating around their suns in exactly the same way as the seven planets of our system. We see only the suns because they are the largest bodies and are luminous, but their planets remain invisible to us because they are smaller and non-luminous. The countless worlds in the universe are no worse and no less inhabited than our Earth.” - GIORDANO BRUNO (1584)

  3. What Is Astrobiology? • Astrobiology is the scientific study of life in the universe, its past, present and future. • Astrobiology seeks to answer three questions: • How does life begin and develop? • Does life exist elsewhere in the universe? • What is life’s future on Earth and beyond? • Astrobiology is an interdisciplinary science • combines biology, chemistry, geology, astronomy, planetary science, paleontology, oceanography, physics, and mathematics to answer these questions.

  4. Where would we start the search for life outside our Solar System? First, find a habitable world

  5. What Is a Habitable World? A world that can maintain liquid water on its surface

  6. Challenges: Separating Planet and Star In the visible, they don’t give off their own light They are VERY far away, which makes them very faint They are lost in the glare of their star

  7. Learning About the Planet • We will not be able to see details on it • Everything we learn will be “disk-averaged”. • The signs of life must be a global and on the surface • Our interpretation is only as good as how deep we can see!

  8. Learning About Distant Worlds Radio Infrared Visible Ultra- Violet X-Ray Gamma Rays

  9. Greenhouse Warming Δ 37 C Δ 520 C A planet’s greenhouse effect is at least as important in determining that planet’s surface temperature as is its distance from the star! After Table 9.1, Bennet, Shostak, Jakosky, 2003

  10. So Many Planets… • 211 planets known beyond our Solar System! • But there’s ONE problem…

  11. Too Big! • These planets are mostly “giant planets” • Small, rocky, Earth-like terrestrial planets around good parent stars are still very difficult to find. • A handful of M < 10 Earth masses known • Recent discovery of Gl 581c, > 5.1 Mearth R. Hasler

  12. Hi! How can we tell if a planet is inhabited? DEAFENING SILENCE! Without direct contact with an alien civilization, or travelling to the nearest solar system, our best chance for finding life in the Universe is to look for global changes in the atmosphere and surface of a terrestrial planet.

  13. Signs of Life • Astronomical Biosignatures are global-scale photometric, spectral or temporal features indicative of life. • Earth shows us that life can provide global-scale modification of: • A planet’s atmosphere • A planet’s surface • A planet’s appearance over time • Biosignatures must always be identified in the context of the planetary environment • e.g. Earth methane and Titan methane

  14. Signs of Life: Atmosphere O3 CH4

  15. Signs of Life: Surface Reflectivity

  16. Signs of Life: Time NOAA-CMDL

  17. A Diversity of Worlds

  18. A Diversity of Worlds in Space… Circularity Star-Planet Distance Water Content Wet Dry

  19. Modern Proterozoic Archean …and Time

  20. Earths Around Other Stars

  21. Earth N2O AD Leo planet CH4 O3 + CH3Cl H2O CO2 Active M Star Planets N2O Earth-like planets around M stars with similar surface fluxes can produce simultaneous strong signatures of O2 or O3 and CH4, CH3Cl or N2O.

  22. Early Earth-like Planets

  23. Modern Earth 355ppm CO2

  24. Proterozoic 0.1PAL O2 100ppm CH4 15% decrease in ozone column depth Segura, Krelove, Kasting, Sommerlatt,Meadows,Crisp,Cohen

  25. Archean N2 99.8% 2000ppm CO2 1000ppm CH4 100ppm H2 Karecha, Kasting, Segura, Meadows, Crisp, Cohen

  26. High CO2 Early Earth-like Planet

  27. High CO2 Early Earth-like Planet

  28. The Coevolution of Photosynthesis with the Atmosphere On Extrasolar Worlds

  29. Why Are Plants Green?

  30. Terrestrial Planet Finders Terrestrial Planet Finder NASA Direct detection of planets Launch… ? Darwin ESA

  31. http://vpl.ipac.caltech.edu http://planetquest.jpl.nasa.gov

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