The scientists analysed what are called shergottite meteorites. These are fairly young meteorites that originated by partial melting of the Martian mantle — the layer under the crust — and crystallised in the shallow sub-surface and on the surface.
They came to Earth after they were ejected from Mars some 2.5million years ago. Investigating their geochemistry tells scientists a lot about the geological processes the planet underwent.
'We analyzed two meteorites that had very different processing histories,' explained Dr Hauri. 'One had undergone considerable mixing with other elements during its formation, while the other had not.
'We analyzed the water content of the mineral apatite and found there was little difference between the two even though the chemistry of trace elements was markedly different.
'The results suggest that water was incorporated during the formation of Mars and that the planet was able to store water in its interior during the planet's differentiation.'Based on the mineral's water content, the scientists estimated that the Martian mantle source from which the rocks were derived contained between 70 and 300 parts per million (ppm) water. By way of comparison, the upper mantle on Earth contains approximately 50-300 ppm water.