Molecular Species Precursors to Life

Two research teams were searching for negatively-charged ions called anions. Both teams reported postive findings in the July 20 edition of the Astrophysical Journal Letters, according to a press release from the National Radio Astronomy Observatory (NRAO).

Anthony J Remijan of NRAO, who is the lead investigator for one group, said that the discoveries add to the "number of paths available for making the complex molecules and other large molecular species that may be percursors to life...." Jan M. Hollis of NASA's Goddars Space Flight Center (GSFC) said, "...this means that there are many more ways to build large organic Molecules in cosmic environments than have been explored." Hollis worked with Remijan's team.

Sandra Brueken of the Harvard-Smithsonian Center for Astrophysics (CfA), who headed the second team of researchers, said: "...it appears that many more probably exist. We believe that we can discover more new
Both research groups used data from the Robert C. Byrd Green Bank Telescope (GBT), which is a radio telescope in Green Bank, Virginia. GBT is the largest fully steerable radio telescope in the world. Radio telescopes detect and record radio waves coming from celestial objects, in this case, interstellar molecules. Laboratory experiments disclose which radio frequencies are emitted by targeted molecules. These radio fquency patterns are then compared to the frequencies being picked up by the radio telescope until an identifying match is found.

GBT is unique in that its support structures are external to the dish surface, this frees up the entire surface figure to pick up signals. Additionally, GBT has "a wheel-and-track design that allows the telescope to view the entire sky above 5 degrees elevation," according to the GBT Web page. More over, the 2,004 panels that surface it's asymmetrical dish (100 meters by 110 meters) are individually adjusted by way of motor-driven piston mountings (actuators) for high precision accuracy of radio wave reception. Images of GBT in various positions are available in the GBT photo gallery.

The discoveries of these two anions, following after the discovery of a first one in 2006, will make a fundamental revision of theoretical models of interstellar chemistry a neccessity. As Hollis said that, "Until recently, many theoretical models of how chemical reactions evolve in intersteller space have largely neglected the presence of anions. This can no longer be the case...."

Discussing how astronomers had thought that intersteller molecules could not hold an extra negative electron --thus creating a negatively-charged molecule--for a significant length of time, Mike McCarthy of CfA said: "That obviosly is not the case. Anions are surprisingly abundant in these [interstellar] regions."

Both teams found negatively-charged octatetraynyl, which is a chain of eight carbon atoms and one hydrogen atom. It was most likely formed in a sequence beginning with a C2H molecule attaching to a C6H2 molecule (C8H2) that would then receive a charge of ultraviolet light (radiation) from a star. The radiation would break one hydrogen bond leaving one positively-charged ion and one free negatively-charged electron. This electron would attach to the C8H chain (formed from the C8H2 chain less one hydrogen). This chemical reaction would release a burst of radiation and leave a negatively-charged octatetraynyl C8H- anion. The artist conception describes this process.

One of the two newly discovered anions was found in the gaseous envelope surrouding an old, evolved star. The other was in a cold, dark intersteller cloud. As Remijian said, the anions were found "in the giant clouds from which stars and planets are formed."

Dave Finley, NRAO and David Aguilar, CfA, "Intersteller Chemistry Gets More Complex With New Charged-Molecule Discovery." National Radio Astronomy Observatory. URL: http://www.nrao.edu/pr/2007/biganion/