NASA recognizes the biological effects of lunar dust as one of its Strategic Knowledge Gaps. Lunar dust is defined as lunar regolith with grains of smaller than 100µm. The average grain size is ~70µm but can be found in a variety of shapes and sizes, though most are slightly elongated. Lunar regolith has low electrical conductivity, allowing individual dust grains to retain electrostatic charge.[i] The combination of these properties – in combination with other properties that we know little about (e.g. toxicity, reactivity, etc.) – are important to understand before large-scale crewed missions to the moon can become feasible. NASA classifies an understanding of the biological effects of lunar dust as enhancing knowledge for shorter (28-day) crewed missions to the moon and enabling knowledge for longer human stays on the moon.[ii] Because this is a piece of enabling knowledge for longer human stays on the moon, it is critical for sustainable lunar infrastructure development.
Earth-based testing of the biological effects of lunar dust has been partially retired as a strategic knowledge gap – lunar samples collected by the Apollo missions give us some insight into the particle size distribution, microscopy, and passivation and reactivity of lunar dust. However, in situ testing is required to fully understand the properties of lunar dust in a lunar environment. Specifically, three in situ measurements are needed:
a) Particle size distribution and dust shape morphology studies of the smallest particulates from varied sample sites
b) Grain-clump adhesion strength and clump size distributions
c) Passivation experiment to determine grain reactivity as transported from intrinsic environment into normal atmosphere
This research area is fairly straightforward; the main challenge for is that the test can only be performed in the actual environmental setting for us to understand the electrostatics and cohesion of small grains of lunar dust in the plasma and electrical environment of the moon.
No missions have been proposed to study this, but the SSERVI RISE4 team has previously performed some Earth-based testing on grain reactivity. No details were available on the experiment design.
[i] Stubbs, T.J., et al., Impact of Dust on Lunar Exploration, 2007.
[ii] Strategic Knowledge Gaps, Theme 2.