Meteoric Evidence Suggests Mars May Have a Subsurface Reservoir

It is a scientific fact that water exists on Mars. Though most of it today consists of water ice in the polar regions or in subsurface areas near the temperate zones, the presence of H²O has been confirmed many times over. It is evidenced by the sculpted channels and outflows that still mark the surface, as well as the presence of clay and mineral deposits that could only have been formed by water. Recent geological surveys provide more evidence that Mars’ surface was once home to warm, flowing water billions of years ago.

But where did the water go? And how and when did it disappear exactly? As it turns out, the answers may lie here on Earth, thanks to meteorites from Mars that indicate that it may have a global reservoir of ice that lies beneath the surface.

Together, researchers from the Tokyo Institute of Technology, the Lunar and Planetary Institute in Houston, the Carnegie Institution for Science in Washington and NASA’s Astromaterials Research and Exploration Science Division examined three Martian meteorites. What they found were samples of water that contained hydrogen atoms that had a ratio of isotopes distinct from that found in water in Mars’ mantle and atmosphere.

This new study examined meteors obtained from different periods in Mars’ past. What the researchers found seemed to indicate that water-ice may have existed beneath the crust intact over long periods of time.

As Professor Tomohiro told Universe Today via email, the significance of this find is that “the new hydrogen reservoir (ground ice and/or hydrated crust) potentially accounts for the “missing” surface water on Mars.”

Basically, there is a gap between what is thought to have existed in the past, and what is observed today in the form of water ice. The findings made by Tomohiro and the international research team help to account for this.

“The total inventory of “observable” current surface water (that mostly occurs as polar ice, ~10E6 km3) is more than one order magnitude smaller than the estimated volume of ancient surface water (~10E7 to 10E8 km3) that is thought to have covered the northern lowlands,” said Tomohiro. “The lack of water at the surface today was problematic for advocates of such large paleo-ocean and -lake volume.”

In their investigation, the researchers compared the water, hydrogen isotopes and other volatile elements within the meteorites. The results of these examinations forced them to consider two possibilities: In one, the newly identified hydrogen reservoir is evidence of a near-surface ice interbedded with sediment. The second possibility, which seemed far more likely, was that they came from hydrated rock that exists near the top of the Martian crust.

“The evidence is the ‘non-atmospheric’ hydrogen isotope composition of this reservoir,” Tomohiro said. “If this reservoir occurs near the surface, it should easily interact with the atmosphere, resulting in “isotopic equilibrium”.  The non-atmospheric signature indicates that this reservoir must be sequestered elsewhere of this red planet, i.e. ground-ice.”

While the issue of the “missing Martian water” remains controversial, this study may help to bridge the gap between Mars supposed warm, wet past and its cold and icy present. Along with other studies performed here on Earth – as well as the massive amounts of data being transmitted from the many rover and orbiters operating on and in orbit of the planet – are helping to pave the way towards a manned mission, which NASA plans to mount by 2030.

The team’s findings are reported in the journal Earth and Planetary Science Letters.

Further Reading: NASA