PANSPERMIA
PANSPERMIA
The conjecture that life originated in space or another planet.
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A SETI Institute team builds interstellar clouds in simulation chambers at very low temperatures and pressures, like those in the outer regions of the solar nebula. They work with chemicals we know are present in comets to learn how complex organic materials form in icy bodies like comets. Their experiments have produced complex organic compounds like those we find in the debris of comets, the meteorites. When added to water, some of these materials form tiny (10 micron diameter) capsule-like droplets similar to cell membranes. Extracts of organics from some meteorites also form these capsule-like droplets when added to water. This intriguing result points to the possibility that comets and meteorites could have salted the Earth with organic materials that were a springboard for life.
. . An estimated 1,000 to 10,000 tons of dust and rock land on Earth each day from space.
In 1953, Dr. Stanley Miller and Dr. Harold Urey at the University of Chicago conducted an experiment to see if the basic building blocks of life —amino acids and sugars— could be formed from the basic chemicals they believed were readily available on the early Earth: methane, hydrogen, ammonia, and water. They built a closed system that cycled the chemistry between liquid and gas phases, and added energy—a spark—to mimic lightning. After some time passed, many compounds formed, including some of the amino acids found in our cells. This experiment catapulted them to world fame, and created the new scientific field of exobiology, the study of life beyond Earth, because it appeared that the basic building blocks of life could arise from inorganic materials, water, and energy. More simply, given the right stuff and the right conditions, planets can make the primordial soup where the chemistry of life can form. And, scientists reasoned, it could happen elsewhere. More recently, NASA has coined the term, astrobiology to encompass the study of life beyond Earth.
. . Today, the next generation of scientists are considering that the organics could have arrived later (when the Earth had cooled a bit). They could have arrived as comets and meteorites that rained down water for oceans, carbon dioxide for the atmosphere, and organics to contribute to the origin of life.
. . Like the Miller-Urey experiment, the Astrochemistry Laboratory results are only suggestive; they point to a cosmic source for some of the building blocks of life. Bernstein, Allamandola, and Sandford described their research in Scientific American.
. . Of course, a huge gap still yawns between even the most complex organic compounds and the genetic code, metabolism and self-replication that are crucial to the definition of life. But given their omnipresence, if organic molecules from space had something to do with life here, that means they were—and always are—available to help with the development of life elsewhere. "Life's Far Flung Raw Materials"
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