Early solar system created life building blocks

Meteorite analysis reveals crucial transformation processes

Tagish Lake Meteorite © NASA / JSC, Mike Zolensky
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They are considered the most pristine and pristine meteorites ever found on Earth: the Tagish Lake Fragments. Now, a chemical analysis has detected both amino acids and other building blocks on these asteroid fragments. As researchers in "Science" report, the originating asteroid must have undergone a change 4.5 billion years ago, which caused these molecules to emerge - and probably made other meteorites "life-giving" for the early Earth.

Meteorite impacts are sometimes a danger to us humans, but more often a valuable opportunity. For the carbonaceous chondrites among them, stony chunks with globules of organic matter, are like time capsules that give researchers important insights into the early history of our solar system. Most of the organic molecules conserved in them originate from the original cloud, the disk of dust and gas in which the planets originated. However, variations and composition of these substances also allow conclusions about which processes changed the original building blocks.

Uniquely untouched meteorite fragments

A research team led by geologist Chris Herd of the University of Alberta has now analyzed samples of a carbonaceous chondrite that exploded in January 2000 over Tagish Lake in northern British Columbia. It is considered unique in its conservation status as it burst 30 to 50 kilometers above the ground and its fragments fell on the frozen and snow-covered lake. They were thus largely protected from contamination by terrestrial organic material. Even the discoverer of the meteorite fragments had consulted with experts before collecting the chunks and therefore avoided any direct contact with the rock samples.

It is precisely this untouched state that makes the Tagish Lake meteorites a valuable reservoir for organic molecules that have already been introduced with the rock from space. Their analysis sheds light on which chemical building blocks could possibly have reached our planet by meteorite impact in the early days of the earth.

Amino acids and other life building blocks

Already the investigations of the rock composition of the samples showed that the originating asteroid must already have undergone major changes in space. The chemical analyzes of the organic components proved similar. The range of insoluble organic molecules detected in the meteorite is so great that it covers the entire spectrum of all substances ever found in carbonaceous chondrites. display

In addition, the researchers found high concentrations of various monocarboxylic acids (MCA) and numerous amino acids both crucial building blocks for the origin of life. The composition of the amino acids corresponds to that typical for extraterrestrial sources. But they also point to extensive change processes in the early history of the original asteroid.

Transformation process already in the early solar system

"The mixture of prbiotic molecules, so essential to the genesis of life, depended on what was happening out there in the asteroid belt, " explains Herdrt stove. "The geology of the asteroid has an influence on which molecules actually reach the surface of the earth." According to the scientists, the asteroid already became a green one shortly after the formation of the solar system Subjected to their conversion.

When the asteroid arose in the cloud of gas and dust, it probably contained ice first. However, as the young planetary system evolved, environmental conditions changed and the ice melted. However, the liquid water reacted with the organic substances in the asteroid and changed the geological and chemical composition of the rock in a way that is still detectable today about 4.5 billion years later.

"Taken together, these results suggest that the chemical and thermal changes in the Tagish Lake meteorites occurred when the fragments were still part of a larger parent object, " explains Larry Nittler of the Carnegie Institution. This came from the same raw material that shaped our solar system. The samples therefore also provide valuable information on the origin of the organic material and life on Earth. (Science, 2011; DOI: 10.1126 / science.1203290)

(University of Alberta / Carnegie Institution, 10.06.2011 - NPO)