Releasing Atmospheric Martian Dust in Sand Grain Impacts

TL;DR

This study experimentally investigates how impacts of sand grains on Martian soil can eject fine dust particles, revealing that even cohesive small grains can be emitted, contributing to Martian atmospheric dust.

Contribution

The paper provides laboratory evidence linking impact conditions to dust emission sizes, highlighting the emission of sub-micrometer dust despite cohesive forces.

Findings

Dust ejection includes particles smaller than 1μm.

Ejection probability follows a power law with particle size.

Impacts can emit dust in the size range suspended in Mars atmosphere.

Abstract

Emission of dust up to a few micrometer in size by impacts of sand grains during saltation is thought to be one source of dust within the Martian atmosphere. To study this dust fraction, we carried out laboratory impact experiments. Small numbers of particles of about 200\textmu{}m in diameter impacted a simulated Martian soil (bimodal \textit{Mars Global Simulant}). Impacts occurred at angles of $\sim 18^\circ$ in vacuum with an impact speed of $\sim 1 \rm m/s$. Ejected dust was captured on adjacent microscope slides and the emitted particle size distribution (PSD) was found to be related to the soil PSD. We find that the ejection of clay sized dust gets increasingly harder the smaller these grains are. However, in spite of strong cohesive forces, individual impacts emit dust of 1\textmu{}m and less, i.e. dust in the size range that can be suspended in the Martian atmosphere. More generally, the probability of ejecting dust of a given size can be characterized by a power law in the size range between 0.5\textmu{}m and 5\textmu{}m (diameter).