Adsorption and thermoanalytical studies on the CI chondrite Orgueil as case of early preplanetary matter

• Orgueil’s physisorption properties are comparable with Earth-like phyllosilicates.
• Thermal mass loss up to 1100 °C amounts to 25 wt% including 5–10 wt% space water.
• 1021 kg of Orgueil-like material (mass of Ceres) could have brought all Earth’s water.
• The results may support in-situ data evaluation of surface missions to asteroids.

The thermal, adsorption, and, in particular, the water-bearing properties of the CI-type meteorite Orgueil as an example of early preplanetary matter have been studied by quantitative sorption experiments with H2O, CO2, N2, and n-heptane, thermogravimetry/differential scanning calorimetry as well as by coupled thermogravimetry/mass spectroscopy. The study contributes to a detailed examination of the behavior of volatile species in carbonaceous chondrites and could support future surface missions on asteroids. The results confirm the presence of phyllosilicates, sulfates, carbonates, and presumably carbon in Orgueil. The decomposition fragments observed during the thermoanalytical experiment indicate somewhat lower temperatures of decomposition for the sulfates. The nature of the distinct partial step around 970 K interpreted in terms of a carbon release remains uncertain. The adsorption measurements and thermogravimetric investigations suggest the presence of water-bearing Earth-like minerals such as phyllosilicates. The specific N2 BET surface area is 30 m2/g. The total water quantity present in Orgueil may exceed 10 wt%. At least half of this amount (as a minimum) is very strongly bonded in the water/OH bearing phases of Orgueil.

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