A cold cloud of gas and dust near the center of the galaxy may create the molecular ingredients for life.
By searching the cloud called Sagittarius B2, researchers found the first branched organic chemical discovered in interstellar space: isopropyl cyanide. Its branched structure resembles that of many amino acids, fundamental components of life on Earth that link together to form proteins. The discovery, reported in the Sept. 26 Science, hints that compounds essential to life may arise in the mass of molecules between the stars before making their way to Earth and other planets.
The long-sought discovery corroborates chemical evidence collected from meteorites. Over the last four decades or so, scientists have found more than 80 types of amino acids in meteorites. Though the molecular cargo may assemble on those space rocks, some of the molecules may also be mere passengers, having been formed in dusty gas clouds. Such an interstellar origin would suggest that these basic molecules of life are not unique to the solar system and may seed far-flung planets across the galaxy and perhaps the universe.
But spotting complex molecules in space has been difficult. Using radio telescopes, researchers can record signals at frequencies that are calling cards for individual chemicals. Scientists have detected around 180 molecules in the diffuse matter between the stars. Many were spotted in Sagittarius B2, which is around 26,000 light-years from Earth and contains dense star-forming regions. But most of the identified chemicals have been either simple, straight chains of atoms or ringed structures. In 2003 researchers reported detecting glycine, the simplest amino acid, in Sagittarius B2, but that finding is under dispute.In the new study, researchers parsed the signals from space with a powerful telescope network named ALMA, or the Atacama Large Millimeter/submillimeter Array. ALMA consists of 66 radio dishes located high in the Chilean Andes. Although ALMA had only 20 dishes up and running when Arnaud Belloche and colleagues scanned Sagittarius B2 in 2012, the observatory had high enough resolution to detect the signals of isopropyl cyanide.
The new finding is still not direct proof of molecules essential to life, says Belloche, an astronomer at the Max Planck Institute for Radio Astronomy in Bonn, Germany. But it’s proof that the necessary branched structures are able to form in interstellar space, he says. Astrochemist Eric Herbst of the University of Virginia in Charlottesville, who was not involved in the study, agrees. “This bodes well for the presence of amino acids,” he says.
Researchers are hopeful that ALMA will keep finding previously undetected molecules in distant gas clouds, says astrochemist Jamie Elsila of the NASA Goddard Space Flight Center in Greenbelt, Md. Such new molecules would give scientists a “greater understanding of the rich chemistry occurring in these star-forming regions.”