Washington: A new research has found evidence in meteorites on Earth that indicates Mars has a distinct and global reservoir of water or ice near its surface.
NASA and an international team of planetary scientists' research results support the hypothesis that a buried cryosphere accounts for a large part of the initial water budget of Mars.
Though controversy still surrounds the origin, abundance and history of water on Mars, this discovery helps resolve the question of where the "missing Martian water" may have gone.
The reservoir's existence also may be a key to understanding climate history and the potential for life on Mars. The team's findings are reported in the journal Earth and Planetary Science Letters.
Lead author Tomohiro Usui of Tokyo Institute of Technology in Japan said that there have been hints of a third planetary water reservoir in previous studies of Martian meteorites, but their new data require the existence of a water or ice reservoir that also appears to have exchanged with a diverse set of Martian samples.
The samples revealed water comprised of hydrogen atoms that have a ratio of isotopes distinct from that found in water in the Red Planet's mantle and current atmosphere. Isotopes are atoms of the same element with differing numbers of neutrons.
While recent orbiter missions have confirmed the presence of subsurface ice, and melting ground-ice is believed to have formed some geomorphologic features on Mars, this study used meteorites of different ages to show that significant ground water-ice may have existed relatively intact over time.
Researchers emphasized that the distinct hydrogen isotopic signature of the water reservoir must be of sufficient size that it has not reached isotopic equilibrium with the atmosphere.
Co author John Jones said that the hydrogen isotopic composition of the current atmosphere could be fixed by a quasi-steady-state process that involves rapid loss of hydrogen to space and the sublimation from a widespread ice layer.
Curiosity's observations in a lakebed, in an area called Mount Sharp, indicate Mars lost its water in a gradual process over a significant period of time.
Co-author Conel Alexander added that in the absence of returned samples from Mars, this study emphasizes the importance of finding more Martian meteorites and continuing to study the ones they have with the ever-improving analytical techniques at our disposal.
The study is published in the journal Earth and Planetary Science Letters.
