All of us air breathers won't asphyxiate to death anytime soon but news from the science world the Earth's oxygen levels continue to drop is a puzzle begging to be solved.

The Earth's not losing life threatening amounts of oxygen, however. Scientists trying to explain the mystery of the vanishing oxygen said oxygen levels have only fallen by 0.7 percent over the past 800,000 years. But it's a trend and that's worrisome.

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A new study published in the journal, Science, by Princeton University professor Daniel Stolper presents data measured from small air bubbles trapped in ice on Greenland and Antarctica that suggest Earth's oxygen levels continue to fall.

Air bubbles trapped within ice provides clues to the atmospheric composition at the time of "deposition" and can be analyzed for paleo-oxygen levels. The study found that over the past 800,000 years, the amount of oxygen in the atmosphere fell by 0.7 percent and continues to drop. It reassures everyone that the 0.7 percent decline can't cause significant problems for life on Earth.

Scientists said oxygen levels are controlled by complex global systems that tend to regulate and dampen large swings from the average. This makes it a difficult task to pinpoint why exactly oxygen levels have been falling for almost a million years.

Scientists, however, have several hypotheses to explain the steady and persistent decline.

One hypothesis is a global increase in erosion rates has led to a steady decline in free oxygen within the atmosphere. In a process similar to iron rusting (where iron binds with oxygen during oxidation), weathering rocks can remove free oxygen from the atmosphere.  Good receptors for oxygen during oxidation are pyrite, or fool's gold, and organic carbon.

Another hypothesis is tied to the global on-average cooling seen for the past 56 million years since the Paleocene-Eocene Thermal Maximum (PETM). This prolonged cooling period cooled the global oceans, allowing them to hold more dissolved oxygen through increased solubility.

It's a scientific fact liquids can hold more dissolved gas when cooler and this might have led to more oxygen dissolved into the Earth's oceans. This, in turn, might be responsible for the gradual decline in atmospheric oxygen concentrations.

TagsOxygen, Earth, Daniel Stolper, Princeton University, erosion, weathering, oceans, water