In “NASA: DNA Found on Meteorites Indicates Life May Have Originated in Space” (The International Business Times, August 9, 2011 12:51 PM EDT), they say:
Researchers from NASA’s Goddard Space Flight Center in Greebelt, Md., report evidence that ready-made DNA parts could have crashed to the surface on objects like meteorites, and then assembled under Earth’s early conditions to create the first DNA.
The discovery was made using samples from 12 carbon-rich meteorites, nine of them from Antarctica. The team extracted small fragments of the meteorite and ran them through a process to determine their structure. What they found was adenine and guanine. These are two of the nucleobases needed to make the rungs of DNA’s spiral ladder (in addition to thymine and cytosine, which were not present in the sample).
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The Department of Chemistry at Duke University discusses some of the past experiments, like the Miller-Urey experiment, that have been done regarding producing amino acids from simple compoungs:
In 1953, Stanley L. Miller and Harold C. Urey, working at the University of Chicago, conducted an experiment which would change the approach of scientific investigation into the origin of life.
Miller took molecules which were believed to represent the major components of the early Earth’s atmosphere and put them into a closed system.
The gases they used were methane (CH4), ammonia (NH3), hydrogen (H2), and water (H2O). Next, he ran a continuous electric current through the system, to simulate lightning storms believed to be common on the early earth. Analysis of the experiment was done by chromotography. At the end of one week, Miller observed that as much as 10-15% of the carbon was now in the form of organic compounds. Two percent of the carbon had formed some of the amino acids which are used to make proteins. Perhaps most importantly, Miller’s experiment showed that organic compounds such as amino acids, which are essential to cellular life, could be made easily under the conditions that scientists believed to be present on the early earth. This enormous finding inspired a multitude of further experiments.
In 1961, Juan Oro found that amino acids could be made from hydrogen cyanide (HCN) and ammonia in an aqueous solution. He also found that his experiment produced an amazing amount of the nucleotide base, adenine. Adenine is of tremendous biological significance as an organic compound because it is one of the four bases in RNA and DNA. It is also a component of adenosine triphosphate, or ATP, which is a major energy releasing molecule in cells. Experiments conducted later showed that the other RNA and DNA bases could be obtained through simulated prebiotic chemistry with a reducing atmosphere.
There has been a recent wave of skepticism concerning Miller’s experiment because it is now believed that the early earth’s atmosphere did not contain predominantly reductant molecules. Another objection is that this experiment required a tremendous amount of energy. While it is believed lightning storms were extremely common on the primitive Earth, they were not continuous as the Miller/Urey experiment portrayed. Thus it has been argued that while amino acids and other organic compounds may have been formed, they would not have been formed in the amounts which this experiment produced.
Many of the compounds made in the Miller/Urey experiment are known to exist in outer space. On September 28, 1969, a meteorite fell over Murchison, Australia. While only 100 kilograms were recovered, analysis of the meteorite has shown that it is rich with amino acids. Over 90 amino acids have been identified by researchers to date. Nineteen of these amino acids are found on Earth. The early Earth is believed to be similar to many of the asteroids and comets still roaming the galaxy. If amino acids are able to survive in outer space under extreme conditions, then this might suggest that amino acids were present when the Earth was formed. More importantly, the Murchison meteorite has demonstrated that the Earth may have acquired some of its amino acids and other organic compounds by planetary infall.