Slide 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?” (

Slide 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 ”.

Slide 3Fig , p.428

Slide 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)

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

Slide 6 Basic Requirements of Life Carbon Electrons Energy Water Other nutrients

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

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

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

Slide 10 Extremophiles Organisms living in extreme habitats on Earth Who, what, & where are they? Genetic Diversity Metabolic Diversity

Slide 11 Genetic Diversity

Slide 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)

Slide 13 Metabolic Diversity (cont’d.) Microbial life exhibits these strategies and many 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 )

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

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

Slide 16 Some Categories of Organisms Adapted to Extreme Habitats - Low pH (< 5) - High pH (> 9) - No O 2 -Within rock -High salinity -High hydrostatic pressure -Very cold temp. -Very hot temp. -Very limited H 2 O AcidophilesAcidophiles AlkaliphileAlkaliphile AnaerobeAnaerobe EndolithEndolith HalophileHalophile BarophileBarophile PsychrophilePsychrophile ThermophileThermophile XerophileXerophile

Slide 17 Deep Sea Hydrothermal Vents

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Slide 19 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)

Slide 20 Habitable Worlds 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 Photo of Jupiter with moons Europa (near Red Spot) and Callisto (left) Cassini Spacecraft image.

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Slide 24 Fig , p.601

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Slide 26 Fig , p.518

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Slide 28 Fig. 15-2, p. 307

Slide 29 Fig , p.602

Slide 30p.188

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Slide 33 Life in the Universe 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). Hubble Space Telescope image of Sedna- takes 10,500 years to circle the Sun! Interplanetary Dust Particle -10 µm across made by dying and exploded stars

Slide 34 Table 26-1, p.607

Slide 35 Fig , p.606

Slide 36 Arecibo Radio Observatory (Puerto Rico) 305-meter diam. Phoenix Project 1995-present survey of 1000 nearby stars at freq. of 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

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Slide 38 Allen Telescope Array (Hat Creek, California) 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 ( GHz) at each pointing. Over 50 dishes are already in place and taking data for several projects.

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