Evidence for a dynamo in the main group pallasite parent body.

Structure and Chemistry of Pre-cursor Troilite in Pallasites

Introduction: Pallasites are widely considered to be poor in sulphide, as such little is known about troilite evolution and processing. Very few examples exist indicating the multiple stages of troilite evolution. Discussed here are two such samples of FeS structures one is a nickel enriched FeS grain in the main group pallasite Hambleton. The other is a series of micron FeS particles within ol...

Textural Evidence for Melt Processes on the Pallasite Parent Body

Geochemistry and oxygen isotope composition of main-group pallasites and olivine-rich clasts in mesosiderites: Implications for the “Great Dunite Shortage” and HED-mesosiderite connection

Evidence from iron meteorites indicates that a large number of differentiated planetesimals formed early in Solar System history. These bodies should have had well-developed olivine-rich mantles and consequentially such materials ought to be abundant both as asteroids and meteorites, which they are not. To investigate this “Great Dunite Shortage” we have undertaken a geochemical and oxygen isot...

Nickel Isotopic Compositions in Pallasites and Iron Meteorites

We report Ni isotope ratio results for Ni from metal in iron meteorites and from metal and olivine in pallasites. The investigation of pallasites was undertaken because (1) previous work on pallasites showed evidence for in situ decay of Mn (t1⁄2 = 3.7 Ma) in olivines [1,2] and of Pd (t1⁄2 =6.5 Ma) in metal [3]; (2) evidence for the in situ decay of Fe (t1⁄2 = 1.5 Ma) in eucrites [4,5]; (3) pos...

Energetics of Asteroid Dynamos and the Role of Compositional Convection

Introduction It has recently been argued that the observed paleomagnetism of angrite meteorites is most likely due to an early dynamo on the angrite parent body [1]. On Earth and other large silicate bodies, dynamo activity is thought to be sustained by a combination of thermal and compositional buoyancy [2]. Here I will argue that compositional buoyancy, if present, overwhelmingly dominates th...