Transcript Astrobiology

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”.
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Fig. 20-18, p.428
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
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Carbon
Electrons
Energy
Water
Other nutrients
Earth’s timescale
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Fig. 26-9, p.599
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
Genetic
Diversity
•
Metabolic
Diversity
Who, what, & where
are they?
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Genetic
Diversity
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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
live
Hydrothermal vent
bacteria
(Divediscovery.whoi.edu)
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Extremophiles on Earth
• Many examples of tolerance to extreme
environments
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temperature
pressure
salinity
pH
desiccation
radiation
Life in Extreme Environments
• Examples of extreme habitats &
extremophile inhabitants
–Potential environmental stressors
–Some physiological adaptations
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Some Categories of Organisms Adapted to
Extreme Habitats
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Acidophiles
Alkaliphile
Anaerobe
Endolith
Halophile
Barophile
Psychrophile
Thermophile
Xerophile
- Low pH (< 5)
-
High pH (> 9)
No O2
Within rock
High salinity
High hydrostatic pressure
Very cold temp.
Very hot temp.
Very limited H2O
Deep Sea Hydrothermal Vents
www.noaa.gov
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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)
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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
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Fig. 26-10, p.601
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Fig. 23-16, p.518
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Fig. 15-2, p. 307
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Fig. 26-11, p.602
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p.188
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Life in the Universe
Hubble Space Telescope
image of Sednatakes 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).
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Interplanetary Dust
Particle -10 µm across
made by dying and exploded stars
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Table 26-1, p.607
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Fig. 26-14, p.606
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
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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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