Satellites burning up on re-entry could cause climate change
Companies are launching thousands of satellites in worldwide networks, creating “mega-constellations” of satellites in low Earth orbit at 330km-2,000km altitude, and the number of satellites is expected to reach more than 60,000 by 2030.
The skies are becoming overcrowded, and many older, obsolete satellites are becoming space junk. Elon Musk’s SpaceX has been deorbiting its old Starlink satellites into the Earth’s upper atmosphere, where they burn up. In future, thousands of old satellites are expected to be burnt up this way each year. But using the atmosphere as a rubbish incinerator may cause grievous harm to the atmosphere and to global weather patterns. When Starlink satellites re-enter and burn up in the atmosphere, they create about 30kg of aluminium oxide vapour, a substance that damages the ozone layer in the stratosphere. The ozone layer helps to shield the Earth’s surface from the sun’s harmful ultraviolet radiation, which can lead to skin cancer and cataracts in humans. And the pollutants from old satellites can remain suspended in the upper atmosphere for decades.
This problem first came to light in February 2023 when Nasa flew an aircraft over Alaska at 60,000ft (18km) to collect aerosol particles in the stratosphere. It found these samples contained aluminium and other metals that came from satellites burning up in the upper atmosphere. Flights over the stratosphere in Antarctica found similar particles. “Our measurements were not looking for the metals from spacecraft re-entry and we were surprised to find them,” Dan Murphy at the US National Oceanic and Atmospheric Administration said.
The re-entry of satellites and space debris can not only damage the Earth’s atmosphere but also pose risks to the global climate. Studies suggest that the aluminium dust could accumulate between 10km and 30km above the Earth’s surface and heat the stratosphere and the layer of atmosphere above that, the mesosphere, by up to 1.5C over Antarctica. That in turn could lead to a weakening of the Antarctic polar vortex in the stratosphere, a key component of the climate, and possibly changing global wind patterns.