Paris: What happened to all the water that once sloshed in lakes and oceans on Mars? Much of it, researchers proposed Wednesday, may be locked up in stone.

 Previous studies had concluded that the water was swept into space by powerful solar winds when the planet’s magnetic field collapsed, while some was captured in sub-surface ice.

 But this did not account for all the missing water.

 To try to track down the rest, an international team of researchers put scientific modelling to the test.

 “The results revealed that the basalt rocks on Mars can hold approximately 25 percent more water than those on Earth, and as a result drew the water from the Martian surface into its interior,” said a statement from Oxford University, where scientists took part in the study.

 As on Earth, chemical weathering and hydrothermal reactions can change minerals in rock from dry to water-bearing, study co-author Jon Wade of Oxford told AFP.

Agence France-Presse