While studying the survey data, co-authors Tapasi Ghosh, an Arecibo astronomer, and Mayra Lebron, a former Arecibo astronomer now at the University of Puerto Rico "said, Something looks an awful lot like a spectral line here, and we said, Pull our other leg," Salter told National Geographic News.
"Slowly, we became convinced."
The team has also looked for direct evidence of glycine but has seen none of its telltale chemistry.
To date, more than 140 molecules have been identified in space, mostly in the neighborhood of the Milky Way. (Get a Milky Way wallpaper.)
Esteban Araya is an astronomer at New Mexico Tech in Socorro and the National Radio Astronomy Observatory.
He said the discovery of methanimine in Arp 220, along with "abundant circumstantial evidence, such as the short time it took life to appear on the early Earth, suggest that life ... may be quite common in the universe."
Moreover, he said, the discovery shows complex organic molecules can exist in very inhospitable environments, such as starburst regions.
The shake-ups during rapid star formation probably created the molecules in the first place—but the chance that they'll yield complex life in such a wild scene is low, Araya pointed out.
"Nevertheless, it is possible that some of the methanimine ... will be trapped in dust grains and will enrich the interstellar medium of Arp220," he said.
"When the tumultuous present activity of Arp220 settles down, new generations of stars like our sun may be formed, and some of the organic molecules trapped in dust grains may enrich newly formed planets."
(Related: "Many 'Earths' Are Out There, Study Says [April 6, 2005].)
Rallying Cry for Arecibo
Astronomers predict that the new discovery will touch off new observation programs at the world's largest radio telescopes, including Arecibo, the National Radio Astronomy Observatory's Green Bank Telescope in West Virginia, and the Very Large Array in New Mexico.
Heightened interest in what such scopes can offer the search for extraterrestrial life will be a shot in the arm for Congressional funding that has been waning, the researchers hope.
Arecibo, in particular, has appeared headed for closure if proposed funding cuts materialize.
"These findings show how important Arecibo Observatory can be for the search of biologically important molecules in space," said Héctor Arce, an astrophysicist at Yale University.
"If Arecibo was able to detect molecules from a galaxy [250 million light-years] away, imagine its potential for searches of complex molecules in our own galaxy."
Salter and his colleagues do have plans to turn Arecibo's power toward the Milky Way—if they can.
Meanwhile, they're pushing ahead with the remainder of their Arp 220 survey.
With a little more analysis, they say, they can be more certain about preliminary evidence that methanol—another organic molecule of interest—can also be found in the galaxy.
And they're eager to tackle a list of 20 other starburst galaxies within reach of the telescope, which could contain similarly exciting molecules, Salter said.
"We are hoping to show that Arp 220 isn't that much of an oddball."
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