Abstract Following microbial and plant responses to Murchison CM2 meteorite nutrients, further soil fertility parameters are examined. Cohesion of the matrix is tested by dissolving in acidic disaggregation agents, 0.4 M CH 3 COOH, 10% HNO 3 , H 2 SO 4 (pH 3), 50%H 2 O 2 +H 2 SO 4 (pH 3), and saturated CO 2 solution. The responses suggest that carbonates and the organic polymer contribute as cementing agents, and that enhanced disaggregation by H 2 O 2 and diminished disaggregation in saturated CO 2 solutions may contribute to the weathering of carbonaceous meteorites in martian or early Earth environments, respectively. The cation exchange capacities (CEC) of the solid (7.2±0.8 meq/100 g) and powdered Murchison (7.8±1.5 meq/100 g) are comparable. The cation exchange capacity is not reduced by oxidation or acetylation, suggesting that the binding sites of exchangeable cations are mostly inorganic. The CEC correlates with water vapor adsorption similar to that for terrestrial soils. For example, at 20°C and P (H 2 O)=10.8 mbars, 17 mg/g H 2 O is adsorbed on Murchison (CEC=7.2 meq/100 g) and only 0.6 mg/g on Allende (CEC=0.4 meq/100 g). Under these conditions 13 H 2 O molecules are adsorbed per surface cation in Murchison and 8 H 2 O molecules/cation in Allende, similar to 9 H 2 O molecules/cation in terrestrial soils and in montmorillonite. Adsorption isotherms on the Murchison are convex at low pressures, indicating strong bonding of the first water molecules, and concave at high pressures, indicating a broad pore size distribution. Isotherms at 278, 293, and 311 K yield isosteric heat of adsorption of 56.5±2.5 kJ/mol at 4–8 H 2 O adsorbed molecules/cation, similar to that for montmorillonite. The isotherms yield a specific surface area of S w =37×10 3 m 2 /kg for Murchison, larger than the 19×10 3 m 2 /kg of pure serpentine, suggesting contributions, in addition to the main serpentine-like phyllosilicates, by components equivalent to a 9–12% smectic clay-like content. Water evaporation curves from meteorite surfaces display the multistage behavior typical of soils, with slow rates for the evaporation of surface-adsorbed water. The gas adsorption data allow an assessment of gas-adsorbed water equilibrium in the solar nebula and suggest possible self-catalytic effects in adsorption/aqueous alteration processes. The observed fertility indicators and biological effects support the potential of carbonaceous chondrites to support early biological processes and as soils for space-based agriculture.