A new analysis of the mineral composition of meteorites suggests that theories concerning the development of the early solar system may need revision. Announcing their results today in the journal Science, researchers conclude that it took the earth only 20 million years to form from material floating around the early sun. Previous estimates, in contrast, had placed that figure at around 50 million years. The findings also re-open the debate over which types of supernovae could have produced our solar system.
Measuring the amounts of an isotope of the element niobium (niobium-92) and its daughter isotope zirconium-92 in two meteorite samples provided the researchers with a kind of radioactive chronometer capable of estimating the timing of events in the early solar system. The earlier calculation of 50 million years for the formation of the earth was obtained using the same technique. But this time, the experimenters made sure to avoid contamination of their samples. By paying greater attention to maintaining the purity of the samples, says study co-author Brigitte Zanda-Hewins of Rutgers University, the team was able to produce a more accurate estimate. Additionally, the new, lower figures for the abundance of niobium-92 (which is generated by supernovae) in the early solar system, Zanda-Hewins says, loosen the constraints on the types of supernovae that could have spawned the solar system. The floor is once again open for candidates.