How did the building blocks of life arrive on Earth? Zinc fingerprints in meteorites offer clues

Researchers used chemical fingerprints of zinc in meteorites to determine the origin of volatile elements on Earth. The results suggest that without “unmelted” asteroids, there may not have been enough of these compounds on Earth for life to emerge.

Volatiles are elements or compounds that turn into vapor at relatively low temperatures. They include the six most common elements in living organisms, as well as water. Zinc found in meteorites has a unique composition, which can be used to identify sources of terrestrial volatiles.

Researchers from the University of Cambridge and Imperial College London have already discovered that the zinc on Earth comes from different parts of our solar system: about half comes from beyond Jupiter and the other half closer to Earth.

“One of the most fundamental questions about the origin of life is where the materials we need for life to evolve come from,” said Dr. Rayssa Martins of the Department of Earth Sciences at Cambridge. “If we can understand how these materials appeared on Earth, it could give us clues about where life originated here and how it might emerge elsewhere.”

Planetesimals are the main building blocks of rocky planets, such as Earth. These small bodies form through a process called accretion, in which particles around a young star begin to stick together and form larger and larger bodies.

But not all planetesimals are equal. The first planetesimals formed in the solar system were exposed to high levels of radioactivity, causing them to melt and lose their volatile substances. But some planetesimals formed after these sources of radioactivity were extinguished, which helped them survive the fusion process and further preserve their volatiles.

In a study published in the journal Scientific advancesMartins and his colleagues examined the different forms of zinc that arrived on Earth from these planetesimals.

The researchers measured the zinc in a large sample of meteorites from different planetesimals and used the data to model how Earth got its zinc, tracing Earth’s entire accretion period, which lasted for tens of millions of years.

Their results show that while these “molten” planetesimals represented about 70% of the Earth’s overall mass, they only provided about 10% of its zinc.

According to the model, the rest of Earth’s zinc came from materials that did not melt or lose their volatile elements. Their findings suggest that unmolten or “primitive” materials were a key source of volatiles for Earth.

“We know that the distance between a planet and its star is a key factor in establishing the conditions necessary for that planet to maintain liquid water on its surface,” said Martins, the lead author of the paper. study. “But our results show that there is no guarantee that planets contain the right materials to have enough water and other volatiles, regardless of their physical state.”

The ability to trace elements through millions or even billions of years of evolution could prove an essential tool in the search for life elsewhere, such as on Mars or on planets outside our solar system.

“Similar conditions and processes are also likely in other young planetary systems,” Martins said. “The role these different materials play in providing volatiles is something we need to keep in mind when looking for habitable planets elsewhere.”