The entry heating and abundances of basaltic micrometeorites

• Published in: Meteoritics & Planetary Science
• Main Author: Genge, MJ
• Other Authors: Science and Technology Facilities Council (STFC)
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Wiley 2017
• Subjects: Science & Technology; Physical Sciences; Geochemistry & Geophysics; COSMIC SPHERULES; ANTARCTIC MICROMETEORITES; COLLECTION; DUST; METEORITES; CRUSTS; BODIES; MODEL; MELTS; ICE; 0201 Astronomical And Space Sciences; 0402 Geochemistry; 0403 Geology; Antarctic; Arctic; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/10044/1/44253; https://doi.org/10.1111/maps.12830

Basaltic micrometeorites (MMs) derived from HED-like parent bodies have been found amongst particles collected from the Antarctic and from Arctic glaciers and are to date the only achondritic particles reported amongst cosmic dust. The majority of Antarctic basaltic particles are completely melted cosmic spherules with only one unmelted particle recognised from the region. This paper investigates the entry heating of basaltic MMs in order to predict the relative abundances of unmelted to melted basaltic particles and to evaluate how mineralogical differences in precursor materials influence the final products of atmospheric entry collected on the Earth's surface. Thermodynamic modelling is used to simulate the melting behaviour of particles with compositions corresponding to eucrites, diogenites and ordinary chondrites in order to evaluate degree of partial melting and to make a comparison between the behaviour of chondritic particles that dominate the terrestrial dust flux and basaltic micrometeroids. The results of 120,000 simulations were compiled to predict relative abundances and indicate that the phase relations of precursor materials are crucial in determining the relative abundances of particle types. Diogenite and ordinary chondrite materials exhibit similar behaviour, although diogenite precursors are more likely to form cosmic spherules under similar entry parameters. Eucrite particles, however, are much more likely to melt due to their lower liquidus temperatures and small temperature interval of partial melting. Eucrite MMs, therefore, usually form completely molten cosmic spherules except at particle diameters <100 m. The low abundance of unmelted basaltic MMs compared with spherules, if statistically valid, is also shown to be inconsistent with a low velocity population (12 km s-1) and is more compatible with higher velocities which may suggest a Near Earth Asteroid sources dominates the current dust production of basaltic MMs.