Charge Detection Mass Spectrometry for the Analysis of Atmospheric Dust on Mars

Abstract

Mars dust is a dominant feature of the planet’s atmosphere and climate, and this dust is likely charged due to natural phenomena such as dust devils and storms. Dust size is also an important characteristic as it pertains to both climatology and risk to current and future Mars exploration. Charge detection mass spectrometry (CDMS) is a technique based on both image charge detection and particle time-of-flight capable of measuring both the charge and mass of individual Mars dust grains. Measurement of these characteristics can be used to determine the particle size distribution. In this work, we report the development of a CDMS instrument made of a printed circuit board (PCB) array for the analysis of microparticles in the Martian atmosphere. Ion optic simulations show that the optimal size range for dust grains analyzed by this device is between 0.2 and 1.5 μm in diameter. Laboratory experiments using three different types of microparticles (derived from Mojave Mars Simulant-1, olivine, and chalkboard dust) show that particles having more than 1500 elementary charges of either polarity can be detected. The average particle velocity measured using time-of-flight for the olivine sample was 24.9 ± 0.4 m/s within the instrument, although different inlet designs or conditions will yield different measurement velocities.