When life began on Earth, iron may have, at first, done magnesium's job, helping to make life possible.
In chemical terms, iron and magnesium are far apart, but new evidence discovered by the NASA Astrobiology Institute (NAI) team at the Georgia Institute of Technology suggests that three billion years ago, iron temporarily did the job magnesium now does in helping ribonucleic acid (RNA), a molecule essential for life, assume the molecular shapes necessary for biology.
There is considerable evidence that the evolution of life passed through an early stage when RNA played a very important role, doing the jobs of DNA and protein before they appeared. During that time, more than three billion years ago, the atmosphere and the environment had no oxygen but had lots of available iron.
"In the new study, researchers from the Georgia Institute of Technology, Atlanta, used experiments and numerical calculations to show that under early Earth conditions, with little or no oxygen around, iron can substitute for magnesium in RNA, enabling it to assume the shapes it needs to catalyze life’s chemical reactions. In fact, it catalyzed those reactions better with iron than with magnesium," according to astrobiology.nasa.gov.
Free oxygen gas was almost nonexistent more than three billion years ago in early Earth’s atmosphere. When oxygen began to be introduced into the environment and atmosphere as a product of photosynthesis, it turned Earth’s available iron to rust, forming massive banded iron deposits that are still mined today. When all that iron got tied up in those deposits, it was no longer available. The current study indicates that RNA then began using magnesium, resulting in life as we know it today," again according to astrobiology.nasa.gov.
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