A unique corundum and refractory metal‐nugget bearing micrometeorite P117

Abstract

Micrometeorites provide a large range of samples sourced from a wide variety of planetary materials, thereby providing a scope for expanding the known inventory of solar system materials. Here we report the micrometeorite AAS62‐34‐P117 having the assemblage of corundum, hibonite, unknown Al‐rich phases, FeNi metal blebs, sulfide, and phosphate embedded in Al‐rich silicate composition, and Pt‐group element nuggets dispersed throughout the micrometeorite. Here, we report the presence of corundum in micrometeorites as a major refractory phase with sizes greater than ~10 μm. The Al‐rich phases have Al2O3 ~50–70%, such high Al phases are not known from meteoritic components either in chondrules or refractory inclusions. In addition, the Ca content is extremely poor to relate it directly to known refractory inclusions, but is very high in Al. The presence of corundum in Al‐rich phases indicates the micrometeorite to be early condensate from solar nebula that later got incorporated into Si‐rich materials leading to a transformation that produced the unusual Al‐rich and Ca‐poor phases different from the average solar composition. The observed texture and mineralogy of the micrometeorite appears to have evolved in a nebular setting that has compositional reservoirs different from those of any known components of meteorites.

Probing the nature of extraterrestrial dust reaching the Earth’s surface collected from the Maitri station, Antarctica

“…The petrographic textures were studied using a scanning electron microscope (SEM, JEOL JSM-IT300LV) fitted with an energy-dispersive spectrometer detector (EDS, AZtecEnergy EDS Microanalysis from Oxford Instruments) at National Institute of Oceanography (NIO), Goa, India, for imaging backscattered electron (BSE) images and identification of different mineral phases. The chemical composition of the identified phases and bulk analyses of major elements from the MMs are analyzed by electron probe microanalyzer (EPMA, Cameca SX5) with four spectrometers at NIO, Goa (Rudraswami et al 2015a(Rudraswami et al , 2015b(Rudraswami et al , 2016(Rudraswami et al , 2017. The conditions set for these analyses are accelerating voltage of~15 kV, beam current of~12 nA, and variable beam size depending on whether it is a spot (~1À2 µm) or bulk (~5À15 µm) analysis.…”

“…Nevertheless, most MM studies have shown particles that are difficult to relate to CAIs and chondrules. There are a few reports of refractory inclusions such as corundum, hibonite, and spinel, which are related to CAI-type objects (Taylor et al 2010;Rudraswami et al 2017). MM SP-155 reported by Taylor et al (2010) has CAI-type mineral phases such as spinel and perovskite enclosed in pyroxene fassaite, closely related to CV chondrites.…”

“…MM SP-155 reported by Taylor et al (2010) has CAI-type mineral phases such as spinel and perovskite enclosed in pyroxene fassaite, closely related to CV chondrites. Besides, MM AAS62-34-P117 collected from deep-sea sediment of the Indian Ocean has shown the presence of corundum, hibonite, and Al-rich phases that are related to refractory inclusion from the early solar system (Rudraswami et al 2017). Moreover, four MMs collected from the South Pole Water Well (SPWW) have shown the presence of rare spinel that has oxygen isotope composition analogous to CAIs of carbonaceous chondrites (Taylor et al 2012;Rudraswami et al 2015b).…”

“…Extraterrestrial dust accretion by the Earth's surface is an important source of information on the micrometeoroid complex, the small particulate matter that is generated by collisions in the asteroidal belt and sublimation of cometary bodies as they approach the inner solar system (Brownlee 2001;Plane 2012). Knowledge related to extraterrestrial dust, both chemical composition and numerical models, has added to our overall understanding of the release of dust from the precursor bodies to entry into Earth's atmosphere, and their survival as micrometeorites (MMs) on Earth's surface (Flynn 1989a(Flynn , 1989bLove and Brownlee 1991;Vondrak et al 2008;Plane 2012;Rudraswami et al 2015aRudraswami et al , 2016Rudraswami et al , 2017Rudraswami et al , 2018.…”

Perceptive of the pyroxene‐bearing micrometeorites and their relation to chondrites

“…; Rudraswami et al. , ). Earlier chemical and isotopic studies on olivine phases of micrometeorites have been largely related to carbonaceous chondrites with minor contribution from ordinary chondrites (Steele ; Kurat et al.…”