Impact ionization mass spectra of anorthite cosmic dust analogue particles

Abstract

Anorthite, the Ca‐rich end‐member of plagioclase feldspar, is a dominant mineral component of the Lunar highlands. Plagioclase feldspar is also found in comets, meteorites and stony asteroids. It is therefore expected to contribute to the population of interplanetary (and circumplanetary) dust grains within the solar system. After coating micron‐ and submicron‐sized grains of Anorthite with a conductive layer of Platinum, the mineral was successfully accelerated to hypervelocity speeds in the Max Planck Institut für Kernphysik's Van de Graaff accelerator. We present impact ionization mass spectra generated following the impacts of anorthite grains with a prototype mass spectrometer (the Large Area Mass Analyser, LAMA) designed for use in space, and discuss the behavior of the spectra with increasing impact energy. Correlation analysis is used to identify the compositions and sources of cations present in the spectra, enabling the identification of several molecular cations (e.g., CaAlO2, CaSiO2, Ca2AlO3/CaAlSi2O2) which identify anorthite as the progenitor bulk grain material.

Charge separation and isolation in strong water droplet impacts

“…27,28 This effect was directly seen in ice particle measurements performed by the dust detector onboard the Cassini spacecraft at Saturn. This method has originally been designed for impact speeds in the order of 10 km s À1 or higher.…”

Calibration of relative sensitivity factors for impact ionization detectors with high-velocity silicate microparticles

“…The creation of sum spectra can be useful in certain cases, e.g., for better visualization of weaker mass peaks in TOF spectra. If applied to the same type of material, or to a certain velocity range, such a procedure increases the signal-to-noise ratio and helps mitigate the effects from variable conditions during the impact ionization process, such as the variable plasma environment and the stochastic nature of the impact process, caused by surface roughness, or projectile size, shape, and orientation (Hillier et al, 2012).…”

“…At higher velocities, the kinetic energy of a particle per volume, i.e., the energy density, is higher. This leads to the break up of molecules and disappearance of the corresponding mass lines (e.g., Hillier et al, 2012). 27 u, 28 u, 40 u, and 56 u are present throughout the almost entire velocity range.…”

“…While qualitative calibration of II-TOF mass spectra has been performed for years using conductive material like metals, carbon and certain polymers (e.g., Stübig et al, 2001;Goldsworthy et al, 2002;Goldsworthy et al, 2003), the detailed study of silicates (e.g., quartz, anorthite, see Hillier et al, 2009Hillier et al, , 2012, became only recently possible due to a relatively new coating technique (Hillier et al, 2009). E.g., for the calibration of the PUMA/PIA instruments, regarding data from Comet Halley, only Fe, Ni, carbon and coated glass particles were available for electrostatic acceleration onto metal targets (e.g.…”

“…List of relevant ions occurring within LAMA mass spectra above 3r, including possible isobaric species at all velocities (afterHillier et al (2012)). In the speed regime investigated here, molecular ions, except small organic species, are of minor or no relevance.…”