As of today, nearly 10,000 satellites are orbiting the Earth and 75% or two-thirds of these 10,000 belong to SpaceX’s broadband constellation, Starlink.
SpaceX has launched more than 6,000 Starlink satellites to orbit, and the company’s promoter Elon Musk is hoping to build a massive constellation of 42,000 satellites. Besides SpaceX, Jeff Bezos promoted Blue Origin’s Project Kuiper also plans to send 3,000 satellites to space, while Airbus-owned OneWeb wants to build a constellation of 648 satellites.
With knack of competition, China too is working to send out whopping number of about 13,000 satellites in space, that will encircle the Earth in the lower orbit (LEO).
A typical 250-kg satellite can produce around 30 kg of aluminum oxide nanoparticles during its demise. These particles may persist in the atmosphere for decades.
The entire population of satellites reentering the atmosphere in 2022 generated approximately 17 metric tons of aluminum oxide compounds. Mega-constellations could lead to over 360 metric tons of aluminum oxide compounds per year, significantly affecting ozone levels. Byproducts from reentering satellites may take up to 30 years to settle from the mesosphere into the stratospheric ozone layer.
At the end of their short lifespan, the satellites generate pollutants as they fall through the atmosphere. Satellite re-entry produces tiny particles of aluminum oxide, which trigger chemical reactions that destroy the stratospheric ozone, according to the recent study published in Geophysical Research Letters. The oxides don’t react chemically with the molecules of the ozone layer; instead they set off destructive reactions between ozone and chlorine that end up depleting the protective layer in Earth’s atmosphere.
Mitigating the risk of ozone depletion due to satellite reentry involves several strategies including designing satellites with deorbiting mechanisms to ensure controlled reentry at the end of their operational life. This minimizes the risk of uncontrolled disintegration and aluminum oxide release.
Plan for reentry trajectories also minimizes the altitude at which satellites disintegrate. Lower altitudes reduce the chances of aluminum oxide reaching the stratosphere.
In addition, exploring materials other than aluminum for satellite construction. Choosing materials that don't produce harmful byproducts during reentry can help mitigate ozone depletion.
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