Over 170 million pieces of space junk pose spacecraft navigational risks in low-earth orbit (LEO). About 30% of all cataloged debris result from two “fragmentation events.” First happens with explosion of Fengyun-1C meteorological satellite in 2007 during Chinese anti-satellite missile test. Second occurs in 2009 when Iridium 33 satellite collides with end-of-life Russian Cosmos 2251 military satellite.
In 1978, Donald J. Kessler anticipates scenario (aka Kessler Syndrome) where object density in LEO causes cascade in future successive collisions, generating effectively impenetrable debris field. Kessler proclaims, “The cascade process can be more accurately thought of as continuous and as already started, where each collision or explosion in orbit slowly results in an increase in the frequency of future collisions.”
International space station repositions more than 30 times to avoid orbital debris. Yet, there’s another larger, growing concern. It’s impact on stratospheric ozone from space debris reentering Earth’s upper atmosphere.
About two decades ago, atmospheric scientists directly sample stratosphere. They document that chemical composition of particulates match naturally occurring meteorites. A decade ago, U.S. General Accounting Office (GAO) claims 200 tons of defunct satellites and upper-stage-rocket boosters annually vaporize in atmosphere. Now, according to Aerospace Corporation data, 800 tons vaporize per year.
Recently, direct samples from stratosphere contained spacecraft metals. These weren’t present before in such high concentrations or just absent. Metals of lithium, aluminum, copper, lead, magnesium and sodium were found in ratios aligning with spacecraft composition. These trace metals resided in 10% of stratospheric-aerosol particles.
Satellite tracking website “Orbiting Now” lists 9,494 active satellites. GAO estimates 58,000 satellites will launch within next six years. Subsequent decommissioning of more LEO satellites raises legitimate concerns about impact on ozone layer. Accounting for recent rocket launches, scientists (Daniel M. Murphy et al., PNAS, Vol. 120, No. 43, 2023) predict that stratospheric-aerosol particulates containing satellite-trace metals will likely rise to 50% upon debris reentry.
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