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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/)

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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 3 Fig. 20-18, p.428

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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)

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Defining Life…on Earth • Life is a chemical system

– in disequilibrium with environment– unique trait of replicating itself– undergoes Darwinian evolution

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

Slide 7 Fig. 26-9, p.599

Earth

’s ti

mes

cale

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

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What is an Extreme Environment?

• Environment that threatens– access to basic requirements– the integrity of biomolecules

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Extremophiles• Organisms living in extreme habitats on

Earth

• Who, what, & where are they?

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GeneticDiversity

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Metabolic Diversity• Macroscopic life

exhibits two main strategies– Photosynthesis

based on excreting oxygen

– Cellular respiration based on consuming oxygen (or other oxygen-containing compounds)

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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 liveHydrothermal vent

bacteria (Divediscovery.whoi.e

du)

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Extremophiles on EarthExtremophiles on Earth• Many examples of tolerance to extreme

environments– temperature– pressure– salinity– pH– desiccation– radiation

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Life in Extreme Life in Extreme EnvironmentsEnvironments• Examples of extreme habitats &

extremophile inhabitants–Potential environmental stressors–Some physiological adaptations

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Some Categories of Organisms Some Categories of Organisms Adapted to Extreme HabitatsAdapted to Extreme Habitats

- - Low pH (< 5)Low pH (< 5)- High pH (> 9)- High pH (> 9)- No O- No O22- Within rockWithin rock- High salinityHigh salinity- High hydrostatic High hydrostatic

pressurepressure- Very cold temp.Very cold temp.- Very hot temp.Very hot temp.- Very limited HVery limited H22OO

• AcidophilesAcidophiles• AlkaliphileAlkaliphile• AnaerobeAnaerobe• EndolithEndolith• HalophileHalophile• BarophileBarophile• PsychrophilePsychrophile• ThermophileThermophile• Xerophile Xerophile

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Deep Sea Hydrothermal Vents

www.noaa.gov

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Life ElsewhereLife 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)

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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) - 2001 Cassini Spacecraft image.

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Slide 24 Fig. 26-10, p.601

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Slide 26 Fig. 23-16, p.518

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Slide 28 Fig. 15-2, p. 307

Slide 29 Fig. 26-11, p.602

Slide 30 p.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 Telescopeimage of Sedna-

takes 10,500 yearsto 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. 26-14, p.606

Slide 36

Arecibo Radio Observatory (Puerto Rico)305-meter diam.

Phoenix Project1995-present survey of1000 nearby stars at freq.of 1000-3000 MHz

Project SERENDIP1979-present “piggy-back” survey using various radio telescopes.Arecibo observations (1992-present) scan each sky pointing every1.7 seconds over 168 million channels centered on 1420 MHz.This enormous data load is farmed out to SETI@home

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Allen Telescope Array (Hat Creek, California)350 6-meter dishes (2008)

This privately-funded (mostly byMicrosoft co-founder Paul Allen)telescope will be primarily usedby the SETI Institute for SETIsurveys. It will be able to scan awide field of view (2.5 degrees)over a wide frequency range(0.5-11.2 GHz) at each pointing.Over 50 dishes are already inplace and taking data for severalprojects.

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