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Aluminium Oxide: A Growing Threat to the Ozone Layer
Context:
A study published in Geophysical Research Letters reveals an 8-fold increase in aluminium oxides between 2016 and 2022 expected to continue as the number of low-Earth-orbit satellites increases.
More on News
- A study by the University of Southern California Viterbi School of Engineering provides an estimate of the extent of long-lived satellite pollution in the upper atmosphere.
- The 1987 Montreal Protocol regulated CFCs to protect the ozone layer, shrinking the Antarctic ozone hole within 50 years, but the growth of aluminium oxide could reverse this progress.
Key Highlights
- Ozone Threat: The huge constellation of satellites launched to meet global internet demand releases ozone-destroying pollutants aluminium oxide during re-entry as they burn up.
- Unanticipated Challenge: Companies like SpaceX and Amazon have launched thousands of low-Earth-orbit satellites, with plans for even more constellations.
- 6,000 of the 8,100 low Earth orbit objects are recently launched Starlink satellites.
- SpaceX is to launch 12,000-42,000 Starlink satellites, while Amazon is to launch constellations of 3,000-13,000 satellites.
- Aluminium Increase in Atmosphere: In 2022, reentering satellites increased atmospheric aluminium by 29.5% over natural levels.
- A 250-kilogram satellite with 30% aluminium mass generates about 30 kilograms of aluminium oxide nanoparticles during reentry.
- Most pollutant particles are created in the mesosphere (50-85 kilometres above Earth’s surface).
- Impact on the Ozone Layer
- Internet Satellites: Internet satellites have a short lifespan (about five years). The continuous replacement of satellites is a contributor to ongoing pollution.
- The stratospheric ozone layer is being destroyed.
- The oxides do not react chemically with ozone molecules, instead causing destructive reactions between ozone and chlorine.
- The aluminium oxides are not consumed by these chemical reactions but instead continue to drift down into the stratosphere, destroying ozone molecules for decades.
- Long-Term Impact: It takes up to 30 years for aluminium oxides to drift to the stratosphere, where 90% of Earth’s ozone is located.
- Accurate pollution modelling: Researchers performed molecular and atomic level modelling of satellite materials.
- Providing information about the chemical composition and interactions of these substances with various energy inputs.
- Future projections:
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- Completion of the planned satellite constellation will result in 912 metric tons of aluminium falling to Earth annually.
- This will release approximately 360 metric tons of aluminium oxide annually, 646% more than natural levels.
Aluminium Oxide (Al2O3) Pollution From Satellites:
- Satellites are often constructed using aluminium alloys due to their lightweight and durable properties. These satellites experience extreme heat and friction during re-entering the atmosphere, causing them to burn up.
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- The burning process breaks down the aluminium and reacts with oxygen to form aluminium oxide nanoparticles.
- Environmental Concerns: It is suspected to react with ozone molecules in the stratosphere, a layer protecting us from harmful ultraviolet radiation.
- Uncertainties and Ongoing Research: The exact extent is still being investigated.
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- Factors like the rate of satellite re-entries, their composition, and the behaviour of aluminium oxide nanoparticles in the atmosphere.
- Potential Solutions:
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- Satellite Design: Exploring alternative materials for satellites with lower environmental impact during re-entry.
- Active Debris Removal (ADR): Developing technologies to remove defunct satellites from orbit before re-entry.
- International Regulations: Establishing international guidelines for satellite design and operation to minimise environmental risks.
- Further Considerations: Research on minimising the environmental impact of satellite re-entry is crucial for sustainable space exploration, balancing its potential benefits like communication, navigation, and Earth observation.