How can astronomical dust fertilize life?

How could the first organic molecules that became the basis of terrestrial biology arise? A study is now shedding light on the possible role of the asteroid dust that once rained down on our planet. Model simulations suggest that this “rich” material may have accumulated extensively in thawing holes on the early Earth. The researchers say the special mixture of matter may have stimulated the prebiotic chemistry that was at the beginning of the evolution of life.

Life always produces new life – but how did the first step come about? How nonliving matter formed complex compounds that enabled self-reproduction and metabolism remains a mystery. In principle, it seems clear that complex organic molecules were initially formed through chemical processes: it is assumed that in the first 500 million years of Earth's history, prebiotic chemistry produced RNA, DNA, and fatty acids. And proteins. These basic elements may have been functionally combined to form the first biological units. However, the earlier formation of the basic building blocks does not seem inevitable. In order for these complex organic molecules to be created through chemical reactions, relatively high concentrations of the elements nitrogen, sulfur, carbon, and phosphorus are necessary. But the corresponding cocktails are difficult to consist of earthy substances because they do not contain high levels of these substances.

Elements of life from space

However, there has long been speculation that asteroids could have provided the relevant quantities, as they are clearly rich in the elements necessary for life. But this interpretation is controversial. Because as pieces, meteorites only deliver material in a limited environment. So the research team led by Craig Walton of the Swiss Federal Institute of Technology in Zurich looked at another possibility: dust from broken-up asteroids could become “fertilizers” for prebiotic processes on Earth. However, it has been objected to date that the material was too widely dispersed to provide relevant quantities of material. “But if you take into account the processes that could have led to concentration, things look different,” Walton says.

To highlight the extent to which cosmic dust can provide prebiotic chemistry, Walton and his colleagues have now developed simulation models. This included assumptions about the extent of previous dust rain. Even today, about 30,000 tons of cosmic dust particles fall to Earth from space every year. But according to researchers, it can be assumed that in the early history of the evolution of our planet, millions of tons fell from repeated collisions of asteroids. The models also included assumptions about conditions on young Earth as well as data about possible accumulation processes of cosmic dust. “Recent research has provided evidence that the Earth's surface cooled and solidified very quickly and large ice sheets formed,” Walton says.

Primordial dust soup in thawing vents

As the team reported, simulations showed that regions with large concentrations of dust could have formed, which were also continuously replenished. Areas of land that were previously covered by ice have emerged as the best places for accumulations. In particular, there could be an effect that is still known today in glaciers and ice sheets: the ice surfaces often appear dirty, and especially in holes where meltwater collects, sediments that were previously thrown onto the ice accumulate significantly. Simulations show that cosmic dust would have been highly concentrated in so-called cryoconite holes.

As the researchers explain, it is possible that the relevant elements were released from dust particles found in these cryoconite vents. Scientists say that once its concentration in water reached a critical threshold, chemical reactions could have started on their own, leading to the formation of the organic molecules that form the origin of life. The low temperatures were not unfavorable either: “Cold does not harm organic chemistry, on the contrary. Walton explains that the reactions are more selective and specific at low temperatures than at high temperatures. For example, it has already been shown that complex organic molecules can indeed form at certain concentrations of substances and temperatures close to the freezing point.

Walton and his colleagues hope their thesis will once again stimulate debate about the origins of terrestrial biology: “Our study will likely cause controversy,” says Walton, “but it may also lead to new ideas about the origin of life.” He and his colleagues plan to back up their theoretical findings with experimental data. Specifically, they want to recreate conditions that might have existed in prehistoric melting holes in laboratory vessels, and then examine whether biologically relevant molecules are formed.

Source: Swiss Federal Institute of Technology in Zurich, specialized article: Physical Astronomy doi: 10.1038/s41550-024-02212-z

© Wissenschaft.de – Martin Viewe