Denver CO (UPI) May 06, 2004
The chemistry that underlies life on Earth is abundant throughout the universe -- in comets, in the interstellar medium, in the atmospheres of planets, in the outer solar system bodies and in living organisms, an astrophysicist told United Press International.
"If these are made everywhere, perhaps life is everywhere," said Emma Bakes, a principal investigator with NASA's Ames Research Center in California and with the SETI Institute. SETI stands for the Search for Extra-Terrestrial Intelligence.
"You have the chemical foundation spread throughout the entire galaxy," she said. "We're not special. I would bet -- if I had a million dollars -- I would bet that life is widespread across the universe."
Bakes spoke on the topic at a meeting of the American Physical Society.
Life's basic building blocks comprise a group of chemicals known as nitrogenated aromatics. They cover a large variety of different compounds and are defined chemically as a carbon skeleton in a ring -- a square, pentagon, hexagon and so on -- with alternating double and single bonds. They are called aromatics because in various combinations they smell of distinctive things, such as bitter almonds and bananas.
With various additions, this alternating, bonded carbon ring makes up pyrroles, purines and pyrimidines, among many other chemicals.
"They form the very foundations of all life on Earth," Bakes said. For instance, half of RNA and DNA molecules consists of purines, and the other half pyrimidines.
They also make up oxygen-producing photopigments in plants, such as chlorophyll, oxygen-storing pigments in animals and enzymes that produce energy.
"The million-dollar question is, 'How do we get from them to us?'" Bakes asked. "It is very tantalizing to think that we can form the basic building blocks of our own genetic code between the stars."
Bakes and other astrophysicists study the composition of the universe by analyzing spectra -- the unique signatures of light either emitted directly by stars or reflected by non-luminous objects, such as planets, moons, asteroids, comets, dust and gas. Using sensitive instruments called spectrometers, scientists can detect elements and compounds at great distances.
Based on such observations, Bakes said nitrogenated aromatics exist throughout the Milky Way galaxy. They can be found in protoplanetary disks around stars, in bodies in the Kuiper Belt -- the loose agglomeration of rocks and planetoids running between the orbits of Neptune and Pluto and beyond -- on comets and in interstellar space.
Nitrogenated aromatics can be formed in a variety of environments. For instance, on comets, they can form in the ice and dust-grain surfaces that are a combination of methane, ammonia, hydrogen and water. In planetary atmospheres, ultraviolet radiation provides the energy for the chemical reactions needed to combine methane and nitrogen into nitrogenated aromatics.
"When we get the interstellar medium collapsing down, it forms a protoplanetary disk around the star," Bakes explained. "We get a lot of interesting chemistry."
She said one hypothesis currently being researched is that comet impacts on Earth could have brought water and life-forming chemicals to the planet. Bakes said this is possible, but added these are fragile molecules. They absorb UV radiation, but when an impact is involved, she added, "you don't know how they are going to react."
Currently, Bakes is studying Titan, Saturn's largest moon.
"Titan is similar to what the early Earth was like," she said, "with an excess of hydrogen and methane and very little oxygen. If we analyze the chemistry of the Titan haze, we can find parallels to what might have happened here on Earth."
On or about Dec. 25 the European Space Agency's Huygens Probe, currently attached to NASA's Cassini spacecraft, will plunge into Titan's atmosphere, setting some of it on fire to determine its composition.
"We'll know what Titan smells like -- I think it is going to smell pretty bad," Bakes said.
"It is well established and becoming more and more clear that the basic organic molecules which seem to have led to the origin of life on Earth -- as best we can reconstruct it -- do seem to be widely distributed in the galaxy," David Grinspoon, principal scientist in the department of space studies at the Southwest Research Institute in Boulder, Colo., told UPI.
"Carbon behaves as if it wants to get together to form complex molecules," said Grinspoon, author of "Lonely Planets," about the possibilities for life elsewhere. "There's no question that this stuff is widely available in our galaxy and presumably in the rest of the universe. If all life needs to get going is these starting materials and a watery place, it's probably common."
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I believe that life exists beyond the Earth. I believe that intelligent life must exist somewhere in the vast universe of stars and galaxies. I recognize that there is, as yet, no evidence to support this belief of mine.
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