First written up in a 1999 magazine article, the work involves creating quinones, substances that help produce photosynthesis in plants and helped build the lab-created membranes that resemble cell walls. A more academically respected version of the article comes in the Jan. 30, 2001, issue of Proceedings of the National Academy of Science.
Life as we know it
All life as we know it involves one or more cells, which are like miniscule factories of chemical production. Many complex chemical reactions have to occur for life to develop.
But in the end, each cell must be surrounded by a protective membrane, the cell wall.
Scientists at NASA's Ames Research Center and the University of California Santa Cruz duplicated the conditions of interstellar clouds of gas and dust, which are the birthplaces of stars. They combined ordinary chemicals common on Earth and in space -- including
, ammonia, carbon monoxide and methanol -- and chilled the mix to near absolute zero (minus 441 degrees Fahrenheit or minus 253 degrees Celsius).The chemicals froze into thin bits of ice. Then, just as a star floods an interstellar cloud with ultraviolet radiation, the researchers zapped their chemical soup with UV rays.
The icy mix transformed into more complex chemical compounds, as expected. But what happened next was a surprise.
When dipped in water, these compounds assembled themselves into membranes similar to those that protect living cells. While the structures are not alive, they show that chemical reactions in space are more complex than traditionally expected.
"This is an enormous step forward in our thinking from not too many years ago, when most scientists believed the chemistry in space was very, very simple," said Louis Allamandola, a NASA astrochemist who led the research team. "The astonishing thing here is that not only is it far more complex than imaginable a short while ago, the chemicals are actually very similar, and in some cases exactly the same as used in living systems today."
Allamandola said the experiment shows that the molecules needed to produce cell membranes, and thus life, are everywhere. "This discovery implies that life could be everywhere in the universe," he said.
Life is not so simple
Others were more cautious about the implications of the findings.
"It is certainly fascinating if the raw material for cell membranes can be cooked up in space," said physicist Paul Davies, author of The Fifth Miracle, which explores how life on Earth might have begun.
But Davies and others point out that the cell membrane was likely the last step in the formation of life. And forming a potential cell wall, or any other inanimate part of a cell, is far simpler than gathering the information, contained in DNA, that powers cells and creates life.
"Bricks are easy to make, because they are simple. Houses are hard because they involve elaborately organized complexity," Davies said. "The same goes for life. The cell membrane is about the simplest feature of the lot."
Matthew Genge, of London's Natural History Museum, said the work "expands the range of very complex organic molecules that can be generated in interstellar space."
Like the scientists involved in the study, Genge points out that this does not mean that life exists in space. But these complex molecules might serve as sort of a ready mix of ingredients for life when delivered to a planet with the right conditions.
Next page: On the verge of biology?
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