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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?

Is Earth the only home forlife in the Universe?

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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 there?

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The Search for Life - Mars• 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.

A picture of Mars and thefoot pad of the Viking lander.

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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:– 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 2004.

Europa

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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.

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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.