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Life in Alternate Environments
Life As We Know It
- the chauvinistic approach
- to survive, life requires the things humans need
- oxygen (O2), water, sunlight
- and requires the absence of things humans can't tolerate
- ammonia, methane, UV radiation
- we define the BIOSPHERE as the envelope of land, air, and surface water on
the Earth where "our kind" of life is found
- we define the CONTINUOUSLY HABITABLE ZONE (CHZ) as the region in
space were a planet can support "our kind" of life
- 0.95 - 1.5 AU around our sun
- we look for extraterrestrial life in places where we could live
The Origins of Life - Beginnings in a Harsh Environment
- from rock and fossil record, know the early Earth (>3.8 b.y. ago)
- had little or no free O2
- no ozone screen to protect surface from UV radiation
- life began in this environment
- using ammonia, methane, CO2, water,
- need absence of either O2 or water for life to start
- eventually, life evolved and modified its environment
- first forms of life were anaerobes - microbes, bacteria, algae, etc.
- don't need free O2 for metabolic functions (O2 is a poison)
- by 3.0-3.8 b.y. ago, evolved photosynthesis - O2-producing
- start to poison their own environment
- evolved amphiaerobes - use O2 when available (more efficient)
- revert to anaerobic processes when O2 not available
- kept O2 levels low for a time
- by 2.0 b.y. ago, had enough O2 available in oceans and atmosphere for
aerobes (strict O2 users) to evolve - the Earth had been altered!
The Earth Continues to Amaze Us - Contemporary Harsh Environments
The Ocean Floor
- studies using submersibles and robots
- conditions at volcanic vents are "hostile"
- high pressures (> 2km below sea level)
- high temperatures - black smokers >150oC
- harmful chemicals - sulfur, CO2
- total darkness - sunlight doesn't penetrate to this depth
- found lush
around these types of vents
- use heat and chemicals from vents
- microbes that like extreme heat, eat hydrogen sulfide, start a food chain
- tubal worms 8-10 feet long
- speculated as origins of life - hot and constant
- shows that "sterile" areas can actually be active
- organisms that survive and thrive in extreme environments
- potential industrial usefulness - organisms have "survival kits" for coping
- given us artificial sweeteners, "stonewash" jeans, genetic identification
- like heat, >45oC up to 150oC
- after 150oC DNA chemical bonds start to dissolve
- some microbes can live in boiling water
- found in/near smokers, hydrothermal vents, hot springs
- cold lovers
- found in arctic sea ice
- like high acidity, pH<5 (water pH=7)
- the acidity is strong enough to destroy DNA
- organisms keep acid out of cell structure
- found in hydrothermal vents, mine tailing and tailing ponds
- like high alkalinity, pH>9 (water pH=7)
- RNA breaks down at pH>8
- organisms keep alkali out of cell structure
- found in soda lakes (in African Rift Valley), carbonate soils
- love extremely salty water
- in salt lakes, salt evaporation ponds
A Few Extreme Examples
worms living on methane ice mounds in the Gulf of Mexico
- mound of water and natural gas (methane is main component)
- these freezes beneath the sediments and seep up as a solid
- temp is 5oC
- water depth is 550 meters
- pink, flat, centipede-like creatures 1-2 feet long, living in dense colonies
- feed on bacteria, which feed on methane
bacteria in the ground, living in pore spaces between rock particles
- 1000's of meters below ground - at high pressure
- reduce sulfates for energy
- have a very slow metabolism - to endure starvation
- cell division occurs on average once per century
- can remain viable for geologically significant lengths of time
Possibilities of Life on
- the Viking lander found no evidence for life
- mass spectrometer found too little carbon
- environment is highly oxidizing
- in past had
early ocean due to warmer climate, denser atmosphere
- was life possible then?
- can we find fossils, or pockets where life survived?
- group of
NASA scientists (Dave McKay and others) found
possible fossils in a Martian meteorite
- is this the origin of life on Earth?
- has the chemical requirements for life
- has a
young icy surface
- kept molten by tidal flexing
- Galileo data shows linear features, rafts of broken ice?
- look similar to fractures in
sea ice in arctic areas of Earth
- is the crust thin - 1km?
- does it overly a
liquid water or slushy asthenosphere?
- water asthenosphere may harbour primitive, microbial
- get energy from volcanic vents at bottom of asthenosphere
- like ocean-floor vents on Earth but much deeper (60 km or more)
- expect volcanic vents at least in early history of Europa
- most geologically active satellite of Saturn
- kept active by tidal stresses
- surface is relatively young
- evidence for tectonic activity
- possibility for slushy asthenosphere at some time in body's history
- has nitrogen and methane atmosphere - similar to Earth except for O2
- can form organic molecules
- surface T is so low that probably have no liquid water
- impacts could melt ice locally - ice pools lasting up to 1000 yrs. may allow life-like chemical reactions to occur
- is hot, and very geologically active
- has plenty of sulfur to sustain sulfur-consuming organisms
Jovian (gassy) planets
- speculation of massive gas-bag organisms (like jellyfish) in atmospheres of gas
- no corroboration for such speculation
Are We Star Stuff? - Extraterrestrial Origins for Life on Earth
Mars - did life evolve on a warm wet Mars and "infect" Earth using Martian
meteorites as the invasion fleet?
- Comets - contain all the chemicals required to manufacture organic molecules
- did they bring the chemicals required to start life on Earth?
- did they bring organic molecules which evolved into life on Earth?
- do they bring viruses to Earth?
- Meteorites - some have been found to contain amino acids
- did the building blocks of life in Earth evolve elsewhere?
- were these responsible for the evolution of life on Earth?
- could these have caused life to evolve on other planets?
- Note: these amino acids aren't found in any living organisms
If you are interested in this topic...
Plan to attend the talk by
Mon. March 9, 1998
at the OISE building
Search for Extraterrestrial Intelligence (SETI)
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