The density and porosity of lunar rocks

[1] Accurate lunar rock densities are necessary for constructing gravity models of the Moon's crust and lithosphere. Most Apollo-era density measurements have errors of 2–5% or more and few include porosity measurements. We report new density and porosity measurements using the bead method and helium pycnometry for 6 Apollo samples and 7 lunar meteorites, with typical grain density uncertainties of 10–30 kg m⁻³ (0.3–0.9%) and porosity uncertainties of 1–3%. Comparison between igneous grain densities and normative mineral densities show that these uncertainties are realistic and that the helium fully penetrates the pore space. Basalt grain densities are a strong function of composition, varying over at least 3270 kg m⁻³ (high aluminum basalt) to 3460 kg m⁻³ (high titanium basalt). Feldspathic highland crust has a bulk density of 2200–2600 kg m⁻³ and porosity of 10–20%. Impact basin ejecta has a bulk density of 2350–2600 kg m⁻³ and porosity of ∼20%.