In two separate studies, scientists mimicked conditions of outer space, doused frozen interstellar cocktails with ultraviolet radiation and created amino acids, which are critical components of life.
The work shows that amino acids could be created around many developing stars, which emit high doses of UV radiation, and that life would have had just as good a chance of forming on planets that might exist around those stars as it did here on Earth.
The studies also support a growing expectation among many scientists that life on Earth may have been seeded from space, rather than having been forged only from raw materials that developed on Earth.
Life's building blocks
All known life is made up of cells built and operated by proteins, which in turn are made from 20 building blocks called amino acids.
Already, scientists have found amino acids in meteorites -- chunks of asteroids or comets that landed on Earth. Amino acids, though not life itself, may have jumpstarted life on Earth with their arrival, some scientists have long suspected. Another theory has held that life on Earth developed out of a soup of lesser materials.
Remarkable as it might be to think of life's ingredients arriving on a space rock, researchers have sought to show that amino acids might also form in interstellar space and thus be ubiquitous. If so, then the raw material of terrestrial life would date back to an earlier time, before comets and asteroids were born.
"Amino acids are literally raining down out of the sky," said one of the team's leaders, Max Bernstein of the SETI Institute and NASA's Ames Research Center, "and if that's not a big deal then I don't know what is."
The laboratory experiments, one conducted by Bernstein's U.S. team and the other by a European group, irradiated mixtures of ice that contained molecules known to exist in interstellar space. The work was done in vacuum chambers under the low temperatures found in space.
The two studies will be presented in the March 28 issue of the journal Nature.
"This finding may shed light on the origin of life itself," Bernstein said. "We found that amino acids can be made in the dense interstellar clouds where planetary systems and stars are made. Our experiments suggest that amino acids should be everywhere, wherever there are stars and planets."
The experiments suggest that Earth may have been seeded with amino acids shortly after it formed, said Jason Dworkin of Ames and the SETI Institute, another member of the team. "And, since new stars and planets are formed within the same clouds in which new amino acids are being created, this increases the odds that life also evolved in places other than Earth."
While no habitable planets are known to exist outside our solar system, scientists fully expect to find them once technology allows.
Yet amino acids are just one group among several substances that are needed to generate life.
"It doesn't mean life," said Joe Nuth, an astrochemist at NASA Goddard Space Flight Center. "It does mean that things are a helluva lot easier in terms of the biochemistry than had been in people's minds in the past."
Many recipes
The U.S effort synthesized three amino acids, called glycine, serine and alanine, in a mixture of water, methanol, ammonia and hydrogen cyanide.
The European team, led by Guillermo Muñoz Caro of Leiden University and Uwe Meierhenrich of Bremen University, synthesized 16 amino acids and several other compounds in a mix of water, methanol, ammonia, carbon monoxide and carbon dioxide. Both groups put together what they thought was a typical composition of interstellar ice. The U.S. group include a much greater portion of water.
Previous experiments by other researchers have yielded various other organic compounds -- though not amino acids -- under a host of conditions.
The differences illustrate a variety of conditions that might generate varying results in real space, experts say. Nearer a star, for example, one set of life's building blocks might be created, while a different configuration would result farther away.
The studies do not address a related and more controversial theory, called
, whose central idea is that life itself -- perhaps in the form of dormant microbes -- arrived on Earth from space.Nuth, who was not involved in the research but is familiar with it, told SPACE.com that the new experiments show that the ingredients for life probably arrived at Earth -- and on other planets -- in a variety of packages. In the end, at least on Earth, just one package was properly mixed and stirred.
Nuth also points out that a host of other stars are known to have formed in a manner very similar to our Sun.
"The likelihood of getting these same precursors to get life started in those systems is moderately high," he said. "It doesn't mean it happened, but it means the chances were the same as on Earth."
Everett Shock, of the Washington University in St Louis, said the results suggest a new path of research.
"You can study geology for a living, but knowing how different rocks form doesnt tell you which lumps of rock will become Teotihuacán, the Taj Mahal or Tonys Tavern," says Shock, writing an analysis of the research for Nature. "Studying the chemical building blocks of life shows that they are ubiquitous and can exist in the absence of life."
Shock said researchers should now focus their efforts on how life might emerge given all these ingredients that are presumed to have been available.
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