Over the recent years, more and more spacecraft have been lifted off into Earth's orbit, and more launches are expected in the near future. The growing number of satellites burning up in Earth's atmosphere has concerned experts, as the environmental impacts of spaceflight are becoming increasingly clear.
Threat From Spacecraft Dust
Satellites from private companies have been a serious concern for astronomers because of their tendency to block cosmic images and interfere with radio telescopes. They also pose increased risk of collisions with other spacecraft.
But the real threat from private satellites actually comes after they die. When satellites end their space missions, most of them deorbit and get burned up in the atmosphere in order to minimize the amount of space debris circling the Earth. However, as they fall apart in flames, the dying satellites leave the upper atmosphere with vaporized metal pollution.
In a new theoretical paper, Sierra Solter-Hunt proposed that this space dust may compromise the magnetosphere, the part of the Earth's magnetic field which protects us from solar radiation. She warns that if the megaconstellations from spacecraft evolve, the amount of dust they release could create a magnetic shield that can limit the reach of the magnetosphere.
Solter-Hunt estimated that around 500,000 to one million private satellites might orbit the Earth in the coming decades. When all of them get burned in orbit, they could increase the amount of dust in the atmosphere up to billions of times its present level.
It is still unclear where all of the dust will end up. However, Solter-Hunt believes that it will settle in the upper layer of the ionosphere and just stay there forever. At this region, the spacecraft dust can create a perfect conductive net around the Earth, capable of carrying an electric charge. If this happens, the magnetosphere would be distorted to stay under the conducting material instead of extending thousands of miles into space.
The reduced magnetic field could expose satellites to high levels of radiation and solar storms, potentially knocking them out of the sky. This means that satellite companies could weaken the magnetosphere with their spacecraft launches, putting themselves at risk as a result.
Even if the magnetosphere does not shrink, the growing amount of spacecraft dust can still make it harder for rockets to lift off new satellites and other spacecraft into Earth's orbit. This is due to the fact that magnetic particles can interfere with onboard electronics. The magnetosphere also undergoes natural weakening as the core of the Earth grows and solidifies. It is still unclear if spacecraft dust can accelerate this process or not.
Other experts are skeptical of the paper's claims, although they agree that there is an urgent need to measure the scale of the space dust problem.
Worst-Case Scenario
In the worst-case scenario, the unchecked expansion of spacecraft dust could create enough invisible conductive shields around our planet, potentially leading to atmospheric stripping. Increased levels of radiation hitting the upper ionosphere could blow away the outer edges of the atmosphere, a phenomenon which has naturally occurred on planets like Mercury and Mars. Solter-Hunt noted that the most extreme cases may take centuries, if not millenia, to happen.
Even if the atmosphere remains intact, it can still get damaged by spacecraft dust. Past studies have shown that some components of space dust, like aluminum oxide, can deplete atmospheric ozone and increase the size of holes above the Earth's polar regions.
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