Mars’s mantle may contain multiple distinct reservoirs of mineral-bound water preserved from the planet’s early history, according to a paper published in Nature Geoscience. The findings suggest that the Martian mantle has a diverse chemical composition and might not have been formed from a global magma ocean.
The isotopic composition of hydrogen on Mars provides insights into different water reservoirs on the planet. Existing models of Mars’s formation have assumed that the mantle has a homogenous hydrogen isotope composition. However, the varied isotopic compositions of Martian rocks and the Martian atmosphere have complicated these models and the identification of distinct water reservoirs in and on Mars.
Jessica Barnes and colleagues analysed the hydrogen isotope composition of minerals from two meteorites from Mars’s crust, where the meteorites interacted with water around 3.9 and 1.5 billion years ago. The authors found that the two meteorites have a similar hydrogen isotope composition. This composition is also similar to more recent material from the planet’s crust, indicating that the composition of water has been consistent for the past 3.9 billion years. The authors compared this to data from other Martian meteorites and found that Mars’s mantle contains at least two reservoirs of mineral-bound water that have distinct hydrogen isotope compositions.
The authors suggest that the differing composition of these reservoirs indicates that Mars may not have been homogenized by a global magma ocean after it formed, as previous research suggested.