Researchers have utilized the chemical signatures of zinc found in meteorites to determine the origins of volatile elements on Earth. Volatiles are elements or compounds that transition into vapor at low temperatures, encompassing the most common elements in living organisms along with water. The distinct composition of zinc in meteorites can help identify the sources of Earth’s volatiles. Scientists from the University of Cambridge and Imperial College London have previously established that roughly half of Earth’s zinc originated beyond Jupiter, while the other half came from closer to Earth.
Accretion is the process in which planetesimals, the primary building blocks of rocky planets like Earth, are formed. These small bodies are created when particles surrounding a young star start to adhere and form larger bodies. However, not all planetesimals are created equal; those formed earliest in the Solar System were subjected to high levels of radioactivity, causing them to lose their volatiles through melting. Conversely, later-formed planetesimals, lacking the same levels of radioactivity, were able to retain more volatiles. In a study published in Science Advances, researchers investigated the different sources of zinc that reached Earth from these planetesimals, tracing the Earth’s accretion process over millions of years.
While the ‘melted’ planetesimals contributed 70% of Earth’s overall mass, they only provided around 10% of its zinc, according to the model. The remainder of Earth’s zinc is believed to have come from materials that did not melt, preserving their volatile elements. This indicates that ‘unmelted’ or ‘primitive’ materials were crucial in supplying volatiles to Earth. The findings suggest that the distance between a planet and its star is a determining factor in establishing the conditions for liquid water on a planet’s surface, but the incorporation of the right materials, such as volatiles, is not guaranteed regardless of a planet’s physical state.
The ability to trace elements over millions or even billions of years of evolution could be pivotal in the exploration for life elsewhere, such as on Mars or exoplanets beyond our Solar System. Understanding the roles of different materials in providing volatiles is essential in the search for habitable planets beyond Earth. The study was supported by Imperial College London, the European Research Council, and UK Research and Innovation (UKRI). The research sheds light on the origin of volatile elements on Earth and their implications for the emergence of life, both on our planet and potentially on other worlds.
