Magma’s Surprising Oxygen Capacity Challenges Earth Science Paradigms
Scientists have discovered that molten rock deep within Earth can store far more oxygen than previously believed. This revelation, published in National Science Review, challenges long-held assumptions about magma’s chemical behavior and suggests a potential mechanism for oxygenating Earth’s early atmosphere. The findings, led by Dr. Yanhao Lin and Dr. Ho-kwang Mao of the Center for High Pressure Science and Technology Advanced Research (HPSTAR), show that under extreme pressures, magma can absorb more than 5% excess oxygen by weight, a capacity not accounted for in traditional models.
High-Pressure Experiments Reveal Oxygen Storage Mechanism
Researchers recreated deep-Earth conditions in laboratories, heating synthetic mid-ocean ridge basalt to 1,200–1,800°C under pressures up to 7 gigapascals—roughly 69,000 times atmospheric pressure. By adding platinum oxide to create an oxygen-rich environment, they found that magma absorbed far more oxygen than expected. At 7 gigapascals, excess oxygen accounted for over 5% of the sample’s weight, compared to just 0.2–0.5% without added oxygen.
Raman spectroscopy detected no sign of gas bubbles, suggesting the oxygen was integrated into the melt’s structure. This suggests magma’s oxygen storage capacity may be even higher than measured, as some oxygen likely escaped during cooling. The results align with computer simulations showing concentrations increasing under pressure.
Oxygen Release from Magma May Have Shaped Earth’s Atmosphere
The study proposes that magma rising from the interior could have released oxygen as pressure decreased, potentially boosting atmospheric oxygen levels billions of years ago. This proposed mechanism may help explain an intriguing coincidence: between approximately 2.5 billion and 2.0 billion years ago, atmospheric oxygen levels underwent major increases.
This mechanism could explain the link between massive volcanic eruptions, such as those forming large igneous provinces (LIPs), and Earth’s atmospheric evolution. However, the exact volume of oxygen reaching the surface remains uncertain, requiring further study.
Implications for Planetary Science and Habitability
The discovery could reshape understanding of magma oceans on early Earth and other rocky planets. If oxygen can be stored and released independently of other elements, models of planetary atmospheric development must account for this process.
However, real basalt's complex chemistry likely allows higher oxygen retention than simplified models indicate.
How Magma Stores Oxygen Under High Pressure?
How does magma store extra oxygen?
Magma absorbs oxygen under high pressure, with experiments showing it can hold more than 5% excess oxygen by weight at 7 gigapascals. This oxygen becomes part of the melt’s structure rather than escaping as gas.
What role did pressure play in the experiments?
Pressure directly influenced oxygen absorption. At normal atmospheric pressure, little excess oxygen was detected, but at 7 gigapascals, concentrations rose sharply. This mirrors how water and carbon dioxide behave under pressure.
Could this explain Earth’s oxygen-rich atmosphere?
The study suggests magma could have released oxygen during volcanic eruptions, potentially contributing to increases in atmospheric oxygen between 2.5 billion and 2.0 billion years ago. However, the exact contribution remains under investigation, with researchers emphasizing the need for further data.
Experimental Pressure Equals 1 Million Pounds per Square Inch
The 7 gigapascal pressure used in experiments equals approximately 1 million pounds per square inch.
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