A team led by scientists at Caltech and the Jet Propulsion Laboratory (JPL), which Caltech manages for NASA, has developed a model, according to which, the levels could even, in theory, exceed the threshold needed to support simple aerobic life.
That finding runs contrary to the current, accepted view of Mars and its potential for hosting habitable environments. The existence of liquid water on Mars is not a given, though.
Discovering liquid water on Mars is one of the foremost goals of NASA's Mars program. In recent months, data from a European spacecraft have suggested that liquid water may lie underneath a layer of ice at Mars's South Pole. It has also been theorized that water could be present in salty subsurface pools.
Oxygen enters water from the atmosphere, dispersing into the liquid to preserve an equilibrium between the water and the air. If salty water were close enough to the surface of the Martian soil, then it could well absorb oxygen from the thin atmosphere.
The team found that, at low-enough elevations, and at low-enough temperatures, an unpredictably high amount of oxygen could exist in the water. This value is quite a few orders of magnitude above the threshold needed for aerobic respiration in Earth's oceans today.