Tag Archives: oxygen

Earth’s inner core may be oxygen-rich

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Oxygen is the key substance for life and one of the most abundant elements in the Earth. However, it’s still unknown whether oxygen is present and in which form in the inner core with extreme high pressure and temperature conditions, and almost composed of pure iron. Scientists co-led by Dr. Jin Liu from HPSTAR (the Center for High Pressure Science &Technology Advanced Research) and Dr. Yang Sun from Columbia University reveal that Fe-rich Fe-O alloys are stable at extreme pressures of nearly 300 GPa and high temperatures of more than 3,000 K.

The results published in the journal of The Innovation prove that oxygen can exist in the solid inner core, which provides key constraints for further understanding of the formation process and evolution history of the Earth’s core.

The Earth’s solid inner core, as one of the most mysterious places on the planet, is in the most extreme temperature and pressure environment on Earth, with a pressure of more than 3 million atmospheres and a temperature close to the surface of the Sun, about 6000 K. Because the inner core is far beyond the reach of humans, we can only infer its density and chemical composition from the seismic signals generated by earthquakes.

Iron-rich Fe–O compounds at Earth’s core pressures/CREDIT:Jin Liu


Iron-rich Fe–O compounds at Earth’s core pressures/CREDIT:Jin Liu

At present, it is believed that light elements exist in the inner core, but the type and content are still debated. Cosmochemical and geochemical evidence suggests that it should contain sulfur, silicon, carbon, and hydrogen. Experiments and calculations also confirmed that these elements mix with pure iron to form various Fe alloys under high temperatures and high-pressure conditions of the deep Earth.

However, oxygen, which is closely related to us, is usually excluded from the inner core. This is mainly because Fe-O alloys with iron-rich compositions have never been found in the surface or mantle environments. The oxygen content in all known iron oxides is greater than or equal to 50 atomic percent. Although people have been trying to synthesize iron oxide compounds with iron-rich compositions, such substances have never been found yet. Is the Earth’s inner core so “anoxic”? To answer this question, a series of experiments and theoretical calculations were carried out in this study.

To be close to the temperature and pressure of Earth’s core, pure iron and iron oxide were placed on the tips of two diamond anvils and heated with a high-energy laser beam. After many attempts, it was found that a chemical reaction between iron and iron oxide occurs above 220-260 GPa and 3000 K. The XRD results reveal that the reaction product is different from the common high-temperature and high-pressure structure of pure iron and iron oxide.

Theoretical crystal structure search using a genetic algorithm proved that the iron-rich Fe-O alloy could exist stably at approximately 200 GPa. Under such conditions, the new Fe-rich Fe-O alloys form a hexagonal close-packed structure, where the oxygen layers are arranged in between Fe layers to stabilize the structure. Such a mechanism produces many close-packed arrangements forming a large family of Fe-rich Fe-O compounds with large configurational entropy.

Based on this theoretical information, an atomic configuration of Fe28O14 was found to match the experimentally measured XRD pattern. Further calculations showed that Fe-rich Fe-O phases are metallic, in contrast with common iron oxides at low pressures. The electronic structure depends on O concentration and the Fe and O layer arrangements. The mechanical properties and thermal properties of the alloy need to be further studied in the future.

Also Read:

What happens when weakening magnetic field creates 3 poles, instead of 2 on Earth?

2 billion years ago, Earth had higher oxygen levels, finds new study of ancient rocks in Russia

Christmas Day sees 61 earthquakes, more than six above average, USGS explains why

 

Wheat prices spike due to climate change: Study

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Rising temperatures are harmful to wheat yields. However, crop yields do not provide a holistic vision of food security. The impacts of climate change on wheat price, livelihood and agricultural market fundamentals are also important to food security but have been largely overlooked.

An international research team has now estimated the comprehensive impact of climate change and extreme climate events on global wheat supply and the demand chain in a 2 ℃ warmer world by using a novel climate-wheat-economic ensemble modelling approach.

The effect of CO2 fertilization could cancel out temperature stress on crops, with a slightly greater wheat yield under 2 ℃ warming as a result. However, increases in global yield do not necessarily result in lower consumer prices. Indeed, the modelling results suggest that global wheat price spikes would become higher and more frequent, thus placing additional economic pressure on daily livelihood.

The findings, by scientists from six countries, were published in One Earth on August 19.

“This counterintuitive result is initially driven by uneven impacts geographically. Wheat yields are projected to increase in high-latitude wheat exporting countries but show decreases in low-latitude wheat importing countries,” said lead author ZHANG Tianyi, an agrometeorologist at the Institute of Atmospheric Physics, Chinese Academy of Sciences.

Co-author Karin van der Wiel, a climate scientist at the Royal Netherlands Meteorological Institute, further explained: “This leads to higher demand for international trade and higher consumer prices in the importing countries, which would deepen the traditional trade patterns between wheat importing and exporting countries.”

Earlier researchers pointed out that trade liberalization would help mitigate climate stress via improving market mobility. The current research team revealed that such policies could indeed reduce consumers’ economic burden from wheat products. However, the impact on farmers’ income would be mixed. For example, trade liberalization policy under 2 ℃ warming could stabilize or even improve farmers’ income in wheat exporting countries but would reduce income for farmers in wheat importing countries.

“These results would potentially cause a larger income gap, creating a new economic inequality between wheat importing and exporting countries,” said WEI Taoyuan, co-author and an economic scientist at the CICERO Center for International Climate Research. ZHANG further explained more dependence on imports could lower the wheat self-sufficiency ratio, thus causing a “vicious negative cycle” for wheat importing and less-developed countries in the long term.

“This study highlights that effective measures in trade liberalization policies are necessary to protect grain food industries in importing countries, support resilience, and enhance global food security under climate change,” said Frank Selten, a researcher at the Royal Netherlands Meteorological Institute and co-author of the study.