Analysis of ablation debris from natural and artificial iron meteorites

Abstract

Artificial ablation studies have been performed on iron and nickel‐iron samples by using an arc‐heated plasma of ionized air. Experiment conditions simulated a meteoroid traveling about 12 km/s at an altitude of 70 km. The artificially produced fusion crusts and ablation debris show features very similar to natural fusion crusts of the iron meteorites Boguslavka, Norfork, and N'Kandhla and to magnetic spherules recovered from deep‐sea Mn nodules. X ray diffraction, electron microprobe, optical, and scanning electron microscope analyses revealed that important mineralogical, elemental, and textural changes occur during ablation. Some metal is melted and ablated. The outer margin of the melted rind is oxidized and recrystallizes as a discontinuous crust of magnetite and wüstite. Adjacent to the oxidized metallic ablation zone is an unoxidized metallic zone in which structures such as Widmannstatten bands are obliterated as the metal is transformed to unequilibrated α2 nickel‐iron. Volatile elements such as S and P are vaporized in the ablation zone. Less volatile elements such as Si and Mn undergo fractionation and are concentrated in the oxide phases, while Ni is concentrated in the metal phases. Dissimilar phases form an intimate intergrowth that persists to a submicroscopic level. Identification of meteor ablation debris in particle collections cannot be based on a single parameter; elemental and mineralogical composition as well as morphological and textural features must be considered.

Implications from chemical, structural and mineralogical studies of magnetic microspherules from around the lower younger dryas boundary (new mexico, usa)

“…Few pulse‐heating experiments have been conducted in order to explain atmospheric entry phenomenon (Blanchard ; Blanchard and Cunningham ; Del Monte et al . , , ; Blanchard and Davis ; Fraundorf et al . ; Sandford and Bradley ; Greshake et al .…”

Rare, metal micrometeorites from the Indian Ocean

“…The melt rim is an excellent evidence for the cosmic origin of micrometeorites and has been produced during experimental ablation studies on carbonaceous chondrites (Toppani et al. ) and on iron meteorites (Blanchard and Davis ). Such melt rims have been commonly observed on unmelted cosmic particles (Kurat et al.…”

Cellular precipitates of iron oxide in olivine in a stratospheric interplanetary dust particle

“…The co-occurrence of iron oxides and taenite is reminiscent of iron meteorite ablation debris (Blanchard and Davis, 1978) where these phases formed as a function of oxidation kinetics. The vesicular texture of a relic Fe,Nisulphide grain supports evaporative loss of sulphur (Rietmeijer, 1993), but in this particle heating resulted in Fe,Ni-sulphide melting with complete loss of sulphur.…”