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Astrobiology: The Search for Life Beyond Earth

Astrobiology investigates the origin, evolution, distribution, and future of life on Earth, as well as the search for life beyond Earth. It addresses three fundamental questions: how does life begin and evolve, is there life beyond Earth and how can we detect it, and what is the future of life on Earth and in the universe?

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Astrobiology: The Search for Life Beyond Earth

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  1. What is Astrobiology? “Astrobiology is the study of life in the universe. It investigates the origin, evolution, distribution, & future of life on Earth, & the search for life beyond Earth. Astrobiology addresses three fundamental questions: 1) How does life begin & evolve? 2) Is there life beyond Earth & how can we detect it? 3) What is the future of life on Earth & in the universe?” (http://astrobiology.arc.nasa.gov/)

  2. Is Life Rare? Hard to image, given the potentially large number of ELPs. But we have no evidence of life outside of our own Earth. Is life common? - Life may be a natural process and part of the universe. - Universe may be full of life. - Earth is not “special”. Is life rare? - Origin of life a rare event, perhaps a singular event despite the abundance of ELPs. - Earth is “special”.

  3. Fig. 20-18, p.428

  4. Defining Life…on Earth • What are the commonly cited traits? • Life does stuff that distinguishes it from other stuff (for instance, computer viruses) • Replicates/reproduces • Uses energy to maintain “chemical disequilibria” • Evolves/adapts • Life does stuff longer than if it weren’t alive (“life evades the decay into equilibrium” - Erwin Schöedinger, 1944)

  5. Defining Life…on Earth • Life is a chemical system • in disequilibrium with environment • unique trait of replicating itself • undergoes Darwinian evolution

  6. Basic Requirements of Life • Carbon • Electrons • Energy • Water • Other nutrients

  7. Earth’s timescale Fig. 26-9, p.599

  8. Harold Urey and Stanley Miller (1953), University of Chicago

  9. What is an Extreme Environment? • Environment that threatens • access to basic requirements • the integrity of biomolecules

  10. Extremophiles • Organisms living in extreme habitats on Earth • Who, what, & where are they?

  11. Genetic Diversity

  12. Metabolic Diversity • Macroscopic life exhibits two main strategies • Photosynthesis based on excreting oxygen • Cellular respiration based on consuming oxygen (or other oxygen-containing compounds)

  13. Microbial life exhibits these strategies andmany more! Photosynthesis & cellular respiration actually performed by “kidnapped” microbes increased ability to find resources under a variety of circumstances  many more niches in which to live Hydrothermal vent bacteria (Divediscovery.whoi.edu)

  14. Extremophiles on Earth • Many examples of tolerance to extreme environments • temperature • pressure • salinity • pH • desiccation • radiation

  15. Life in Extreme Environments • Examples of extreme habitats & extremophile inhabitants • Potential environmental stressors • Some physiological adaptations

  16. Some Categories of Organisms Adapted to Extreme Habitats - Low pH (< 5) - High pH (> 9) - No O2 • Within rock • High salinity • High hydrostatic pressure • Very cold temp. • Very hot temp. • Very limited H2O • Acidophiles • Alkaliphile • Anaerobe • Endolith • Halophile • Barophile • Psychrophile • Thermophile • Xerophile

  17. Deep Sea Hydrothermal Vents www.noaa.gov

  18. Life Elsewhere • Studies of life in extreme environments on Earth have led us to focus on some prime places to look for life • Mars • Europa (moon of Jupiter) • Titan (moon of Saturn)

  19. Habitable Worlds Photo of Jupiter with moons Europa (near Red Spot) and Callisto (left) - 2001 Cassini Spacecraft image. Offers environmental conditions where some form of life could originate or survive. (NOT whether the planet has life or not). Growing evidence for: - Habitability of Early Mars - Habitability of Oceans of Europa (moon of Jupiter) Artists’ rendition of what Early Mars may have looked like

  20. Fig. 26-10, p.601

  21. Fig. 23-16, p.518

  22. Fig. 15-2, p. 307

  23. Fig. 26-11, p.602

  24. p.188

  25. Life in the Universe Hubble Space Telescope image of Sedna- takes 10,500 years to circle the Sun! Our Solar System has planets, dwarf planets, moons, asteroids, comets, and interplanetary dust. Milky Way galaxy has 100 billion (100,000,000,000) stars. Universe has 100 billion (or more) galaxies. Many stars have planets. Some like Jupiter and Saturn. Some may be like Earth. Potential for a large number of Earth-like planets (ELPs). Interplanetary Dust Particle -10 µm across made by dying and exploded stars

  26. Table 26-1, p.607

  27. Fig. 26-14, p.606

  28. Arecibo Radio Observatory (Puerto Rico) 305-meter diam. Phoenix Project 1995-present survey of 1000 nearby stars at freq. of 1000-3000 MHz Project SERENDIP 1979-present “piggy-back” survey using various radio telescopes. Arecibo observations (1992-present) scan each sky pointing every 1.7 seconds over 168 million channels centered on 1420 MHz. This enormous data load is farmed out to SETI@home

  29. Allen Telescope Array (Hat Creek, California) 350 6-meter dishes (2008) This privately-funded (mostly by Microsoft co-founder Paul Allen) telescope will be primarily used by the SETI Institute for SETI surveys. It will be able to scan a wide field of view (2.5 degrees) over a wide frequency range (0.5-11.2 GHz) at each pointing. Over 50 dishes are already in place and taking data for several projects.

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