Introduction: It is well known that breathing in small dust particles can be damaging for your lungs, eyes, and cardiovascular system, and protecting both mechanical and electrical systems from dust is an important design criteria. This is especially true in space, and any sustained human presence on the surface of the Moon or other airless bodies requires careful planning and mitigation of the risks posed by dust grains. Dust grains on moons and asteroids are formed through millions of years of asteroid bombardment, and fine grained regoliths (unconsolidated dust and sand) are known to cover the surfaces of many airless bodies of interest to human exploration. In addition to being small, the dust grains are irradiated with solar wind ions and UV photons, and this irradiation preferentially removes oxygen leaving reactive surface sites. Irradiation can also cause electrical charge to accumulate on the grains, and electrostatic repulsion causes dust grains to repel and 'hop' about the surface. These charged dust grains are very sticky and can cause damage to spacesuits or surface machinery through mechanical friction, disrupt electrical systems through static discharge or field interferences, and cause a toxic response when exposed to biologic materials.
Description: The charged dust project is using a controlled vacuum system to better understand how dust grains gain and lose charge, the effects they have when the come into contact with organic molecules, and methods to passivate the grain surfaces. Analog dust grains (obtained from the CLASS SSERVI node) are placed in an airless environment and then exposed to UV light to charge the grain surfaces. Once the grains are charged, they can be controlled using electrostatic potentials and are transported through a charge measurement column then captured on a conductive plate. The plate can be coated in an organic film, and analysis of the films before and after dust grain exposure can be used to determine the damages caused by the reactive grain surfaces and electrostatic discharging. Gas mediated grain discharging can also be studied by leaking a controlled gas into the vacuum system.
The dust charging project was started after the primary REVEALS grant as a NASA Postdoctoral Program fellowship awarded to Micah J. Schaible. The construction of the dust charging system is nearly complete, and it is anticipated that experiments on this system will begin before the first year of the fellowship ends in September 2019. Preliminary experiments have been carried out to determine the mechanisms of low energy electron damage of nucleotide, amino acid, and phospholipid thin films prepared using a variety of different methods. Using x-ray photoelectron spectroscopy, we were able to identify how the organic molecule was breaking up when exposed to low energy electrons produced by x-ray irradiation. Additional analyses are underway using Raman, florescence, and atomic force microscopy.
Summary: The dust charging project is just kicking off, but we already have exciting results looking into how radiation can damage organic molecules and create potentially toxic reactions in the body. Further work will investigate the effects of charged dust grains with a wide variety of materials to help better prepare human explorers to face the dangers of the space environment.
Take home message: This research will help identify and create mitigation strategies for the dangers of charged dust grains in airless environments such as the surface of the Moon in order to protect sensitive equipment and keep human explorers safe and healthy.