LITTLE GREEN ALGAE:

(SFX: flying saucer noises under all of this)
     ACCORDING TO THE MOVIES, DISCOVERING LIFE ON OTHER PLANETS SHOULD BE
EASY.  THE FLYING SAUCER COMES DOWN, LANDS IN THE CORNFIELD AND SEVERAL
LITTLE GREEN MEN COME OUT AND SAY,

 (SFX:diff voice, "Take me to your leader").  

IN REALITY THAT'S PRETTY UNLIKELY, FOR ONE THING, LIFE TAKES ON ALL FORMS,
NOT JUST TECHNOLOGICAL CIVILIZATIONS LIKE OURS THAT CAN BUILD SPACE
SHUTTLES AND GO TRAVELLING.  HOW CAN YOU TELL IF A FAR AWAY PLANET DOESN'T
HOUSE LITTLE GREEN MEN, BUT ONLY LITTLE GREEN ALGAE? SIMPLE, SAYS
ASTRONOMER ROGER ANGEL AT THE UNIVERSITY OF ARIZONA.  JUST LOOK FOR
OXYGEN.
     
ANGEL: "When the earth was initially formed, there was no oxygen in the atmosphere and that was
created by the process of photosynthesis by blue green alge.  very simple organisms."(034;7s)

PLANTS HAVE A DISTINCTIVE SIGNATURE.  DUE TO PHOTOSYNTHESIS, THE PLANTS
PRODUCE AN ABUNDANCE OF OXYGEN, WHICH CONTRIBUTES TO THE OZONE LAYER
SURROUNDING OUR PLANET.  COVER THE EARTH IN GRASS, FORESTS, EVEN
ONE-CELLED ORGANISMS LIVING IN THE OCEAN, AND IT ADDS UP TO A BIG
FINGERPRINT.

ANGEL: "The ozone in our own atmosphere is caused by life so  . . . if we were to see another planet like
earth and we were to see that it had ozone that could be an indicator that there was life, a very simple form
of life on that planet." (050;20s) 

BY EXAMINING THE LIGHT AND OTHER RADIATION STREAMING OFF A STAR OR PLANET,
ASTRONOMERS CAN TELL WHETHER THERE'S OXYGEN IN ITS ATMOSPHERE.  SO TO
LOOK FOR LIFE, FORGET UFOS JUST LOOK FOR OZONE. FOR SR THIS IS KCF