Introduction
(from the LOOKING FOR LIFE tv special)

"Life as we know it"-for most of us-is the kind of life we see around us every day, on the surface of our planet: with moderate temperatures, using sunlight for energy... and a food web starting with plants.

But when we look for life beyond Earth, we see worlds with very different environments.

Mars is drier than any terrestrial desert, bathed in sterilizing ultraviolet radiation. Saturn's giant moon, Titan, has temperatures so cold that methane falls like rain, and carves deep river valleys. Jupiter's moon, Europa, seems to have a liquid water ocean, buried beneath many kilometers of ice.

Could life exist in such conditions? Did life ever begin on Mars?

These questions are the subject matter of the new science of "astrobiology"-the study of the origin, evolution and future of life. Astrobiologists begin to answer those questions, here on Earth, by looking at life as most of us don't know it... Life more ancient, and more adaptable to extreme conditions than we see around us every day… Life that thrives in places most of us never see. As we search the solar system and beyond, for worlds that might be home to alien life, we broaden our understanding of what life is... by exploring alien environments here on Earth.

Our guides are researchers who take science out of the laboratory, and into the field. We travel to Australia to see if we can prove that life existed 3.5 billion years ago; to Spain, where life thrives in iron-rich acid waters, and a team of NASA researchers tests a drill that one day could be used on Mars; close to the Arctic Circle, we descend into a mine, where life eats rock, and never sees the Sun; we go diving in the highest lake on Earth... where radiation is intense, and find life in abundance.

"LOOKING FOR LIFE" turns out to be a scientific "amazing race" around our planet...

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Program description
In the rust-red Pilbara desert of Western Australia, an international team of NASA and university researchers looks at ancient rocks to see if they offer unambiguous evidence of life on Earth as long ago as 3.5 billion years. Martin van Kranendonk, and Abby Allwood, show shapes they believe could only have been formed by living organisms. Others on the scientific field trip continue to be skeptical. The ongoing debate shows contemporary research as an exciting intellectual adventure, and looking for life in the Pilbara as a physical challenge. Forget to drink often, says Kranendonk, and you could be dead in less than a day! Life, everywhere on Earth, needs water to survive.

At Shark Bay, on the coast and several hundred miles south, Stefan Leuko, a young graduate student at Macquarie University's Australian Center for Astrobiology, dives in chilly waters to sample stromatolites, "living fossils" that may resemble the early life forms seen in the Pilbara rocks. Former Australian Navy engineer, Adrian Brown, tests instruments that could someday fly to Mars, enabling researchers to spot ancient Martian stromatolites - if they ever existed - from orbit.

In the startling red and yellow waters of Spain's Rio Tinto, an intrepid cameraman ventures underwater to show the rich biodiversity of organisms found in some of the most acidic streams on Earth. Ricardo Amils, from Madrid's Centro de Astrobiologia, and Todd Stevens, a geomicrobiologist working with NASA, describe creatures who live underground, never seeing sunlight, feeding on acids and rocks. Nearby, Carol Stoker MARTE project and her team from NASA Ames Research Center and Honeybee Robotics tests a prototype drill that could be deployed to Mars or Jupiter's mysterious moon, Europa. Visit Views of the Solar System, Nine Planets and the Galileo Project.

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North of the Arctic Circle, researchers from Indiana University look for life deep underground, in a soon-to-be closed gold mine, the Lupin Mine, in Nunavut. More than a kilometer underground, Lisa Pratt and colleagues carefully sample water containing evidence of many different kinds of organisms. Working conditions are difficult and dangerous: falling rocks, increasing amounts of methane gas, lots of water. Dr. Pratt provides a "video diary" of her Fall 2005 research expedition, and a first-person account of what she and her team has been finding.

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South of the Equator, high up in the Bolivian Andes, NASA's Nathalie Cabrol dives in the highest waters on Earth, MARS UNDERWATER whose salty shores resemble the ancient lakes recently found on Mars by NASA's rovers, Spirit and Opportunity. In fact, Nathalie, a member of the Explorers' Club, holds the women's high altitude record for free diving! She was also a leading force in targeting Spirit to land in Gusev Crater. In the summit lake, on top of the Licancabur volcano, she and her team find organisms adapted to multiple extreme conditions: winter cold and layers of frozen ice, dangerous ultraviolet radiation, high salinity and yet thriving. She believes their survival in such extremes means that if life ever did begin on Mars, 3.5 billion years ago when conditions may have been warmer and wetter than today, it may perhaps have clung on, deep underground waiting for future missions with drills and instruments especially designed to look for the kinds of life seen throughout the program.

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