Researchers have examined the chemical signatures of zinc found in meteorites to trace the origin of volatile elements on Earth. Their findings indicate that without the presence of ‘unmelted’ asteroids, Earth may not have had sufficient volatiles for life to develop.
Researchers have examined the chemical signatures of zinc found in meteorites to trace the origins of volatile elements on Earth. Their findings indicate that without ‘unmelted’ asteroids, Earth may not have had enough of these compounds for life to develop.
Volatile compounds are substances that turn into vapor at relatively low temperatures, including the six key elements essential for life and water. The zinc present in meteorites has a distinctive composition that can reveal the sources of Earth’s volatiles.
Scientists from the University of Cambridge and Imperial College London have previously determined that Earth’s zinc is sourced from various regions in our Solar System, with about half originating from beyond Jupiter and the other half coming from closer proximity to Earth.
“One of the most essential questions regarding the origin of life is about where the necessary materials for life to evolve came from,” stated Dr. Rayssa Martins from Cambridge’s Department of Earth Sciences. “Understanding how these materials arrived on Earth might provide insights into how life began here and how it might arise elsewhere.”
Planetesimals serve as the fundamental building blocks of rocky planets like Earth. These small entities develop through a mechanism known as accretion, where particles surrounding a young star gradually adhere to one another, forming larger bodies.
However, not all planetesimals are the same. The earliest planetesimals formed in the Solar System were subjected to high radiation levels, causing them to melt and lose their volatiles. In contrast, some planetesimals formed after these radioactive influences had diminished, allowing them to retain more of their volatiles without melting.
In a study featured in the journal Science Advances, Martins and her team explored the various types of zinc that reached Earth from these planetesimals. They analyzed a diverse collection of meteorites from different planetesimals and used this information to model the process through which Earth acquired its zinc over the tens of millions of years it took to form.
The findings reveal that although ‘melted’ planetesimals contributed roughly 70% of Earth’s total mass, they accounted for only 10% of its zinc.
The model indicates that the majority of Earth’s zinc originated from materials that remained unmelted and retained their volatile elements. This implies that primitive materials were crucial in supplying Earth with volatiles.
“We know that a planet’s distance from its star is a crucial factor in creating the right conditions for sustaining liquid water on its surface,” explained Martins, the lead author of the study. “Nonetheless, our results indicate that there is no guarantee that planets will contain the right materials to have sufficient water and other volatiles, irrespective of their physical state.”
The capability to trace elements across millions or even billions of years could be invaluable in the search for life on other planets, such as Mars or exoplanets beyond our Solar System.
“Similar conditions and processes probably exist in other young planetary systems,” said Martins. “The roles that these different materials play in supplying volatiles is an important consideration when seeking habitable planets elsewhere.”
This research was partially funded by Imperial College London, the European Research Council, and UK Research and Innovation (UKRI).
