Lunar Dust: Formation, Microphysics, and Transport

TL;DR

This work delivers an engineering-grade synthesis that links lunar dust production and modification processes to grain-scale properties, bulk thermophysical and dielectric behavior, and near-surface mobilization pathways. By unifying Apollo-era data with modern measurements (Diviner, LADEE/LDEX, CE-4 LPR) and 2024–2025 results (ChaSTE, SCALPSS, NILS), it provides region-specific priors and closed-form relations that propagate microstructure through $k(T,\rho)$ and charge-relaxation to adhesion-limited lofting and near-surface transport. The authors integrate meteoroid ejecta, electrostatic lofting, and rocket-plume entrainment into regional design envelopes, enabling immediate design use for polar traverses, swirls, pyroclastics, and PSRs, and propose measurement priorities to reduce margins. The practical impact is a framework and a set of actionable equations, figures, and tables that translate microphysical dust properties into engineering parameters for upcoming landed and rover missions on the Moon, including considerations for optics, power, thermal control, and mobility in diverse terrains.

Abstract

Lunar dust -- the sub-millimeter fraction of the regolith -- controls the optical, thermophysical, electrical, mechanical, and environmental behavior of the Moon's surface. These properties set the performance envelopes of remote-sensing retrievals, regolith geotechnics, volatile cycles, and exploration systems, while also posing operational and biomedical risks. We synthesize Apollo sample analyses and in-situ observations (Surveyor, Lunokhod, Apollo) with contemporary datasets from the LRO Diviner Lunar Radiometer, the LADEE/LDEX exospheric dust measurements, and Chang'e-4 Lunar Penetrating Radar (LPR). We also incorporate 2024-2025 results: Chandrayaan-3 ChaSTE thermophysics at the Vikram lander's site, SCALPSS plume-surface diagnostics from Intuitive Machines Mission 1 (IM-1), and Negative Ions at the Lunar Surface (NILS) detections of a dayside near-surface H$^{-}$ population on Chang'e-6. The review links (i) production and modification processes to (ii) grain-scale physical/chemical/electrical/optical/mechanical properties, then to (iii) mobilization pathways (meteoroid ejecta, electrostatic hopping, rocket-plume entrainment), and finally to (iv) region-specific design ranges across maria, highlands, pyroclastic units, magnetic swirls, and permanently shadowed regions (PSRs). We quantify temperature-illumination dependence across day/night and PSR-equator regimes through a two-channel $k(T,ρ)$ model and charge-relaxation scaling. We provide closed-form expressions for adhesion-aware lift thresholds and for near-surface (0-3~m) dust transport at apex/hover heights as functions of sheath structure. The result is a design-ready set of relations, figures, and tables that propagate microphysics and composition into engineering parameters for upcoming landed and rover operations.

Figures (3)

• Figure 1: Illustrative conductivity--depth profile $k(z)$ anchored to Diviner day/night trends and the ChaSTE in-situ point at $z\approx 0.08$ m ($k\simeq1.2e-2W\per m\per K$) Hayne2017Paige2010Mathew2025ChaSTE closes the long--standing gap between Diviner surface inversions and near--subsurface $k(z)$. The elevated $k$ at 8 cm is consistent with higher density and local disturbance from landing, emphasizing centimeter-scale structure in $k(T,\rho)$.
• Figure 2: Electric field required to lift a grain of radius $a$ when the charge is limited by $q\approx 4\pi\varepsilon_{0}a\phi_{g}$. Curves show the no-adhesion term $E_{\mathrm{noadh}}(a)$, the adhesion term $E_{\mathrm{adh}}(a)$ for $W=0.1$ J m$^{-2}$ and $R=5~\mu$m using the JKR pull-off $F_{\mathrm{adh}}=\tfrac{3}{2}\pi W R$, and their sum $E_{\mathrm{req}}(a)$. Small red triangles mark $E_{\mathrm{adh}}(a)$ at the same abscissae where open circles mark $E_{\mathrm{noadh}}(a)$. Across the micron range, adhesion dominates and $E_{\mathrm{req}}$ far exceeds typical sheath values ($10^{2}$--$10^{3}$ V m$^{-1}$) unless grains are pre-loosened. Also, adhesion is made explicit via $C_{\rm adh}$, turning electrostatic lift into a pre-liberation criterion rather than a field--only condition.
• Figure 3: Schematic of meteoroid-stream forcing (e.g., Geminids, Szalay2018Geminids) and the resulting transient enhancements in near-surface dust flux. The persistent background is maintained by sporadics; stream spikes modulate injection independent of $E(z)$ (cf. Sec. \ref{['sec:near-surface-0-3m']}). Stream forcing sets event-driven upper bounds on exospheric dust.