Earliest Meteorites Provide New Piece In Planetary Formation Puzzle

The research shows that the process which depleted planets andmeteorites of so-called volatile elements such as zinc, lead andsodium, must have been one of the first things to happen in our nebula.

The implication of this clue is that 'volatile depletion' may be aninevitable part of planet formation - a feature not just of our SolarSystem, but of many other planetary systems too.

The researchers at Imperial College London reached their conclusionsafter analysing the composition of primitive meteorites, coal-likerocks that are older than the earth and which have barely changed sincethe Solar System was made up of fine dust and gas.

Their analysis, published today in the Proceedings of the NationalAcademy of Sciences, shows that all the components that make up theserocks are depleted of volatile elements. This means that volatileelement depletion must have occurred before the earliest solids hadformed.

Dr. Phil Bland, from Imperial's Department of Earth Science andEngineering, who led the research, explains: "Studying meteorites helpsus to understand the initial evolution of the early Solar System, itsenvironment, and what the material between stars is made of. Ourresults answer one of a huge number of questions we have about theprocesses that converted a nebula of fine dust and gas into planets."

For planetary scientists, the most valuable meteorites arethose that are found immediately after falling to earth, and so areonly minimally contaminated by the terrestrial environment. Theresearchers analysed around half of the approximately 45 primitivemeteorite falls in existence around the world.

All of the terrestrial planets in the Solar System as far outas Jupiter, including Earth, are depleted of volatile elements.Researchers have long known that this depletion must have been an earlyprocess, but it was unknown whether it occurred at the beginning of theformation of the Solar System, or a few million years later.

Dr. Phil Bland is a member of the Impacts and Astromaterials ResearchCentre (IARC), which combines planetary science researchers fromImperial College London and the Natural History Museum.