domingo, 1 de abril de 2012

Nebular Clouds --The 'Engines' of Life in the Universe?


Nebular clouds are thought to be most likely environment for synthesizing and promoting the evolution of molecules needed for the origin of life. Giant gas nebulae such as Orion are storehouses of sugars that form ribose -- the backbone of RNA. With a universe full of sugar, it's possible that early RNA worlds were generated and are evolving in their own unique ways throughout the observable universe. RNA coding is what gave primitive cell structures the catalyst they needed to become life.

The Orion Nebula, also known as M42, is one of the brightest and most famous nebulae in the sky. The star forming region's glowing gas clouds and hot young stars are on the right in this sharp and colorful two frame mosaic that includes the smaller nebula M43 near center and dusty, bluish reflection nebulae NGC 1977 on the left. Located at the edge of an otherwise invisible giant molecular cloud complex, astronomers have also identified what appear to be numerous infant solar systems.
Orion is a cosmic zoo, with protoplanetary disks, brown dwarfs, intense and turbulent motions of the gas, and the photo-ionizing effects of massive nearby stars as well as supersonic "bullets" -- each ten times the diameter of Pluto's orbit and tipped with iron atoms glowing bright blue, believed to have been formed one thousand years ago from an unknown violent event.
Over 13 billion years ago at least one of the domains of life may have begun in nebular clouds. If restricted to the Milky Way, which is 13.6 billion years old, the first chemical combinations would have had billions of years to become a self-replicating organism with a DNA genome long before the existence of Earth.
The building blocks for DNA could have been generated or combined within interstellar clouds and DNA would become part of the molecular-protein-amino acid complex. Hydrogen, oxygen, carbon, calcium, sulfur, nitrogen and phosphorus for example are continually irradiated by ions, which can generate small organic molecules which evolve into larger complex organic molecules that result in the formation of amino acids and other compounds. 
Phosphorus, for example, is rare in our solar system and may have been non-existent on the early Earth; phosphorus is essential for the manufacture of DNA.
Polarized radiation in the nebula cloud leads to the formation of proteins, nucleobases and then DNA. The combination of hydrogen, carbon, oxygen, nitrogen, cyanide and several other elements, could create adenine, which is a DNA base, whereas oxygen and phosphorus could ladder DNA base pairs. Glycine has also been identified in the interstellar clouds.
In 2009, the Herschel Space Observatory using the telescope's heterodyne instrument for the far infrared revealed the chemical fingerprints of potentially life-enabling organic molecules in the Orion nebula, one of the most prolific chemical factories in space, although the full extent of its chemistry and the pathways for molecule formation are not well understood. 
By sifting through the pattern of spikes in the spectrum, astronomers have identified a few common molecules that are precursors to life-enabling molecules, including water, carbon monoxide, formaldehyde, methanol, dimethyl ether, hydrogen cyanide, sulfur oxide and sulfur dioxide.
Elsewhere, scientists are using the giant Robert C. Byrd Green Bank Telescope (GBT) to prospect in Sagittarius B2(N), a giant molecular cloud near the center of our Galaxy, some 25,000 light-years from Earth for other new, complex molecules in interstellar space that may be precursors to life.
"Clouds like this one are the raw material for new stars and planets. We know that complex chemistry builds prebiotic molecules in such clouds long before the stars and planets are formed. There is a chance that some of these interstellar molecules may find their way to the surface of young planets such as the early Earth, and provide a head start for the chemistry of life. For the first time, we now have the capability to make a very thorough and methodical search to find all the chemicals in the clouds," said Anthony Remijan, of the National Radio Astronomy Observatory (NRAO).
As molecules rotate and vibrate, they emit radio waves at specific frequencies. Each molecule has a unique pattern of such frequencies, called spectral lines, that constitutes a "fingerprint" identifying that molecule. Laboratory tests can determine the pattern of spectral lines that identifies a specific molecule.
Most past discoveries came from identifying a molecule's pattern in the laboratory, then searching with a radio telescope for that set of spectral lines in a region of sky. So far, more than 140 different molecules have been found that way in interstellar space.
The new study reverses the process. The astronomers will use the GBT to study a cloud of gas and dust in detail, finding all the spectral lines first, then later trying to match them up to molecular patterns using data-mining software.
The astronomers will make a thorough survey of the interstellar cloud in the wide range of radio frequencies between 300 MHz to 50 GHz. This technique, they said, will allow them to discover molecules that would elude more narrow-range observations.
"This strategy wasn't possible at frequencies between 300 MHz and 50 GHz before the GBT. That telescope's tremendous capabilities enable us to open a whole new era of astrochemistry," said Jan M. Hollis, of NASA's Goddard Space Flight Center.
"Based on earlier studies, there are a number of complex, prebiotic molecules that we think are present in such clouds, but only this wide-net approach with the GBT will capture the evidence we need to discover them," Remijan said.
"Complex organic molecules formed in interstellar space are undoubtedly the fundamental building blocks of astrobiology. The complete inventory of such molecules in this cloud will produce a tremendous advance in our understanding of the physical conditions in that cloud and of the first chemical steps toward life," said Phil Jewell, of the NRAO.
As the survey with the GBT continues, the research team plans to release their data to the scientific community. In addition, they are providing software that will allow other scientists to efficiently "mine" the data for the telltale evidence of new molecules.
"There is a wealth of laboratory data now available about the radio fingerprints of many molecules. Data-mining software will make it possible to efficiently match up the spectral lines seen in the laboratory with ones we observe in the interstellar clouds," said Frank Lovas of the National Institute for Standards and Technology.

Source: The Daily Galaxy 

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