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NASA discovers interstellar 'chocolate'

By Robert C. Cowen / October 26, 2005



To solve the mystery of life's origin, scientists can no longer focus solely on Earth. They must take the entire universe into account. Reason: the discovery of nitrogen-carrying aromatic hydrocarbons throughout the universe.

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Prior to their recent discovery in space, scientists had thought these biologically important molecules were unique to Earth. One type is the main ingredient in chocolate. Others carry genetic information in DNA.

The existence of these molecules in interstellar space "was considered impossible" 20 years ago, explains Louis Allamandola, who carried out this research with colleagues at the NASA Ames Research Center at Moffett Field, Calif. "Now, we know better.... As a class, they are more abundant than all other known interstellar polyatomic molecules combined."

The finding has profound significance for the occurrence of organic life. These kinds of molecules are key ingredients in the primordial chemical soup from which scientists think organic life may have arisen.

"Seeing their signature across the universe tells me they are accessible to young planets just about everywhere," says Douglas Hudgins, lead author of the report on this research published in the Astrophysical Journal earlier this month.

In fact, you don't even need a planet to get the organic-life game going.

"This new work shows that the early chemical steps believed to be important for the origin of life do not require a previously formed planet to occur," the Ames announcement explains. "Instead, some of the chemicals are already present throughout space long before planet formation occurs and, if they land in a hospitable environment, can help jump-start the origin of life."

The report exemplifies the kind of 180-degree change in scientific perspective that happens when new research tools uncover new facts. With no data to suggest that these molecules could survive in space, skepticism prevailed.

Then NASA put the Spitzer Infrared Telescope into orbit in 2003 to give astronomers a sharper view of cosmic infrared radiation. The infrared signature of the life-starting hydrocarbons jumped out of the data. Moreover, the Ames team had determined earlier what that signature should look like using advanced computer codes. Comparing those calculated infrared signatures with the Spitzer data confirmed that nitrogen-containing aromatic hydrocarbons permeate the universe. That discovery "changes everything," Dr. Hudgins says.

The notion that earthly life got a helping hand from space harks back to the Greek philosopher Anaxagoras 2,500 years ago. Modern scientists have kicked the idea around for over a century and in recent decades, it has become clear that comets and meteorites bring biologically important chemicals to Earth.

The Deep Impact probe that smashed into the comet Tempel 1 on July 4 revealed a high concentration of organic chemicals beneath the comet's surface. Studies such as those carried out by David Warmflash at the University of Houston and Benjamin Weiss at the Massachusetts Institute of Technology show it is plausible to think some of these chemicals - even living organisms - could reach Earth as stowaways on meteorites that originated on Mars.

Now, it's also plausible to think that the cosmic environment in which the solar system formed contributed to Earth's primordial soup.

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