During the past decade, astrochemists have found that DNA molecules, the fundamental building blocks of life, find their origins not on Earth, but in the Cosmos. They are the languange of the Universe --the information they inherited comes from the stars and the cosmic ecology that formed them.
"Finding these molecules in an interstellar gas cloud means that important building blocks for DNA and amino acids can 'seed' newly-formed planets with the chemical precursors for life," said Anthony Remijan, of the National Radio Astronomy Observatory (NRAO).
One of the newly-discovered molecules, called cyanomethanimine, is one step in the process that chemists believe produces adenine, one of the four nucleobases that form the "rungs" in the ladder-like structure of DNA. The other molecule, called ethanamine, is thought to play a role in forming alanine, one of the twenty amino acids in the genetic code.
In each case, the newly-discovered interstellar molecules are intermediate stages in multi-step chemical processes leading to the final biological molecule. Details of the processes remain unclear, but the discoveries give new insight on where these processes occur. Previously, scientists thought such processes took place in the very tenuous gas between the stars. The new discoveries, however, suggest that the chemical formation sequences for these molecules occurred not in gas, but on the surfaces of ice grains in interstellar space.
"We need to do further experiments to better understand how these reactions work, but it could be that some of the first key steps toward biological chemicals occurred on tiny ice grains," Remijan said.
The discoveries were made possible by new technology that speeds the process of identifying the "fingerprints" of cosmic chemicals. Each molecule has a specific set of rotational states that it can assume. When it changes from one state to another, a specific amount of energy is either emitted or absorbed, often as radio waves at specific frequencies that can be observed with the GBT.
New laboratory techniques have allowed astrochemists to measure the characteristic patterns of such radio frequencies for specific molecules. Armed with that information, they then can match that pattern with the data received by the telescope. Laboratories at the University of Virginia and the Harvard-Smithsonian Center for Astrophysics measured radio emission from cyanomethanimine and ethanamine, and the frequency patterns from those molecules then were matched to publicly-available data produced by a survey done with the GBT from 2008 to 2011.
The researchers are reported their findings in the Astrophysical Journal Letters.
Editors note: DNA is the result of life on Earth, rather than its origin. Over the past decade, molecular paleontologistsand astrochemists have found foundational components of DNA in molecular clouds and stony meteorites, chondrites --agglomorations of cosmic sediments, the original particles present in the solar nebula and protoplanetary disk.
The Gemini Observatory produced the picture of the Lagoon Nebula shown at the top of the page, a star-forming region in the constellation of Sagittarius. The image reveals the composition of the interstellar gas cloud by assigning colours to emissions from different atoms in the nebula.
The Daily Galaxy via The National Radio Astronomy Observatory