Chondrules, a window on the early evolution of the solar system
In a study published on August 6th in the journal PNAS, an international team, led by researchers from IPGP and IUEM, presents an analysis of the evolution of volatile element abundances during the "youth" of our solar system, proposing an explanation for the origin of the differences in chemical composition between Mars and Earth.
Publication date: 08/08/2018
General public, Press, Research
Related teams :
Cosmochemistry, Astrophysics and Experimental Geophysics (CAGE)
Related themes : Origins
The Earth and the other telluric planets (Mercury, Venus and Mars) in the solar system were formed over 4.5 billion years ago, mainly by the agglomeration of small balls of rock called chondrules. Some of these chondrules, early components of the solar system, were trapped in meteorites called chondrites, some of which have been found on Earth. Analyzing the composition of these chondrules opens a window on the youth of our solar system. But the age and formation conditions of the chondrules studied have been the subject of debate within the scientific community for decades.
In this study, researchers have for the first time determined the evolution of volatile element abundances (elements that vaporize easily) in these planetary precursors over the first 4 million years of the solar system, by analyzing chondrules of different ages, previously dated using radio-chronology methods (the so-called “lead-lead” method).
The authors of the study also used the ratio between certain volatile elements (manganese and sodium) as a hygrometer, and were thus able to trace the temporal evolution of oxygen content (from water vapour) in the inner solar system. Their results show a rapid increase in oxygen levels, followed by a decline after a few million years.
As chondrules played a major role in the construction of telluric planets, these results were also used to study the formation of the two best chemically characterized planets: Earth and Mars. A comparison of their chemical composition with the evolution of volatile element abundances in chondrules over time suggests that Mars was formed mainly by the agglomeration of solid materials very early in the history of the solar system, in less than 2 million years, and under relatively oxidizing (water-rich) conditions; whereas the Earth was formed later, under more reducing conditions, as suggested by the analysis of the composition of the most recent and least oxygen-rich chondrules.
Réf : Volatile element evolution of chondrules through time, Brandon Mahan, Frédéric Moynier, Julien Siebert, Bleuenn Gueguen, Arnaud Agranier, Emily A. Pringle, Jean Bollard, James N. Connelly, Martin Bizzarro, Proceedings of the National Academy of Sciences Aug 2018, 201807263; DOI: 10.1073/pnas.1807263115
