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Life in the Universe
Is Earth the only home for
life in the Universe?
• Life is present on Earth nearly
everywhere even under the
most extreme conditions.
• Life survives in boiling hot
springs and in permanently
frozen tundra.
• Life can be found in the
perpetual darkness and
crushing pressures on the ocean
floor.
• Given these extremes, can life
exist on other planets or moons
in our Solar System and around
other stars?
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The Search for Life - Mars
• Among all of the planets
besides Earth, only Mars
appears to have had
conditions that might have
been suitable for life.
• What appear to be dry lake
beds and forms of water
erosion appear on the
surface.
• If liquid water once existed
on the surface of Mars did
life also? Might it still be
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there?
The Search for Life - Mars
A picture of Mars and the
foot pad of the Viking
lander.
• In 1976 the U.S. sent two robotic
landers to study the surface of Mars
to search for signs of life. Chemical
analysis of the soil found no signs of
life.
• In 1996 meteorites found in
Antarctica were determined to be
from Mars. These rocks appeared to
contain fossilized bacteria. Not all
scientists are convinced these are
bacteria, however.
• Several new missions to Mars are
planned in the next few years to
continue the search.
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The Search for Life Elsewhere in Our
Solar System
• Other places in our Solar
System where life is thought
to be possible are:
Europa
– beneath the thick ice on
Europa. Europa may have an
ocean beneath the ice.
– on the surface of Titan. Titan
has a thick atmosphere
composed of gases similar to
that thought to exist on Earth.
• Missions are being planned to
Europa and the Huygens
probe will land on Titan in
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2004.
The Search for Life Around
Other Stars
• By measuring small Doppler
shifts in the spectra of stars,
astronomers have discovered
almost 100 planets.
• So far these planets are
estimated to be as large as
Jupiter or Saturn. No planets
the size of Earth have been
found yet.
• As technology improves
astronomers expect to be able
to find smaller planets and
perhaps to observe them
directly for signs of life. 5
SETI
• Some astronomers have begun
to search for signals coming
from intelligent life elsewhere.
• The Search for Extra Terrestrial
Intelligence (SETI) is collecting
radio data and searching for
patterns that seem artificial.
• This difficult process requires
lots of data and lots of
computing time.
• The SETI@home project
enables anyone with a computer
to help in the search.
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