Scientists find seeds of life in a model of outer space
Scientists at the NASA's Ames Research Center in Mountain View, Calif., reported Monday that by combining simple organic chemicals inside a cold vacuum chamber that replicates the harsh conditions of deep space they have created primitive "cells" that mimic the membrane structures found in all living things.
``This discovery implies that life could be everywhere in the universe,'' said Louis Allamandola, who headed the research team.
``This process happens all the time in the dense molecular clouds of space.''
Scientists have theorized for years that a primordial rain of comets, meteorites and interplanetary dust might have seeded the ancient Earth with chemical ingredients that, in the presence of water and sunlight, led to the emergence of terrestrial life.
The NASA research reported Monday in the Proceedings of the National Academy of Sciences, however, suggests that interstellar space might be more of a chemical crucible than previously thought, and that the rain of cosmic debris early in the Earth's history might have played a bigger role in kick-starting life on the planet.
By exposing chemicals that are known to exist in the swirling interstellar clouds of space that are the birthplace of stars and planets -- water, methanol, ammonia and carbon monoxide -- to ultraviolet radiation, NASA scientists created primitive proto-cells similar to those found in everything from the cells of microorganisms to human beings.
Even though they were formed at temperatures close to absolute zero -- minus 441 degrees Fahrenheit -- when the cells were immersed in water, they spontaneously formed simple membrane structures that contained both an inside and an outside layer.
``The formation of these biologically interesting compounds by irradiating simple interstellar ices shows that some of the organics falling to Earth in meteorites and interplanetary dust might have been born in the coldest regions of interstellar space,'' Allamandola said.
``The delivery of these compounds could well have been critical to the origin of life on Earth.''
In contrast to generally accepted theories of the origins of life, the latest discovery suggests that some of the critical steps that preceded the emergence of life are widespread in space and might need only a hospitable ``Goldilocks'' planet like Earth -- not too hot and not too cold for liquid water to exist -- to go forward.
``All life as we know it on Earth uses membrane structures to separate and protect the chemistry involved in life processes,'' said Jason Dworkin, a member of the research team.
``Membranes are like a house. These molecules were the raw lumber lying around that allowed origin-of-life chemicals to move in and set up housekeeping.''
The most common scientific theory of how life began on Earth is that sometime after the planet formed four billion years ago, the right combination of chemicals and conditions formed a rich chemical soup that eventually led to the emergence of life.
The earliest primitive fossils date from more than three billion years ago.
NASA's new research, however, suggests that the first steps in the chemical process leading to the emergence of life can occur in space -- even in the absence of a planet.
Observations of several comets, including Halley's, Hale-Bopp and Hyakutake, have revealed that those icy wanderers are rife with organic compounds.
The possibility that interstellar space is a vast storehouse of complex organic compounds just waiting for suitable planets to seed is especially important in light of a number of recent discoveries.
Within the past few years, astronomers have discovered more than 50 planets outside our own solar system. Seven new planets were reported in the past month alone.
By virtue of their size and orbits, all of the newly discovered planets are ill-suited for life as it is known on Earth, but the burst of discoveries suggests that many more remain to be found.
By 2006, NASA hopes to launch a space-based telescope able to detect Earth-sized planets orbiting nearby stars.
The possible cosmic origins of the chemical ingredients of biological processes comes as scientists are beginning to think that some of the other planets in our own solar system might have, or at least once had, conditions favorable to life.
In recent years, NASA's Mars missions have shown the cold, arid planet once had ancient shorelines and river channels that could have only been formed by large quantities of water.
Hints of microscopic fossils found in a single Martian meteorite have stirred speculation that primitive life might have emerged there, too, perhaps seeded by the same rain of organic chemicals that showered Earth.