Building blocks of life found in meteorites

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It is believed that simple single-celled life existed on Earth as early as 3.9 billion years ago, that is, as soon as the Earth became cool enough that liquid water could come to the surface. But how could life have arisen so quickly? Scientists have taken a big step forward in answering this question: the research team has identified important building blocks for the DNA of the genetic material in three meteorites. As scientists write in the journal Nature Communications, the found molecules were probably formed in space even before the formation of the solar system.

It has long been known that many organic substances that form the basis of life can already be formed in space. Even amino acids and sugar molecules have already been discovered by researchers in gas clouds and in meteorites that have fallen to Earth. As a result, the hypothesis that the rapid emergence of life on Earth was facilitated by the influx of building blocks of life from space has gained weight. But how far has this cosmic support gone? Yasuhiro Oba of the University of Hokkaido in Japan and his colleagues are currently studying this issue.

Using highly sensitive measuring instruments, the researchers examined three meteorites in the laboratory and discovered additional molecules, namely a wide variety of nitrogenous bases, including adenine, thymine, guanine and cytosine. These four substances are the decisive information carriers of the earth’s DNA. To a certain extent, they hold blueprints for living beings and thus play an important role in ensuring that living beings can reproduce and adapt to their environment through evolution. The actual information is stored in the sequence of nitrogenous bases on DNA and RNA chains.

“Our assay method is optimized to detect nitrogenous bases at the lowest concentration, down to one molecule per trillion molecules,” the scientists say. In fact, they found nitrogenous bases in concentrations up to one in a billion. These frequencies are consistent with the predictions of models describing chemical evolution in the dense gas clouds that form stars and planets.

From this, the researchers conclude that the building blocks of DNA were already formed in gas clouds – even before the formation of the Sun and the Earth. They are apparently stable enough to survive turbulent planet formation, accumulate in dust and rock debris, and then make their way to Earth via meteorites. On the contrary, the formation of such molecules on the young Earth is difficult. “We therefore suspect,” the scientists say, “that nitrogenous bases delivered from space contributed to the genetic characteristics of the first life on Earth.”

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