- A spacecraft that burns up in the atmosphere leaves behind metal particles.
- Scientists are racing to figure out whether it affects the climate.
- One risk is that these particles can cause iridescent clouds and damage the ozone layer.
Satellites and spacecraft that burn up in the atmosphere leave behind metal particles in the stratosphere. Scientists are concerned that it could harm the planet.
Currently, about 10% of particles floating in the stratosphere come from the aerospace industry, but we don't know if this has an impact on the climate.
One risk is that these new particles could seed polar stratospheric clouds. The cloud is a spectacular iridescent cloud that could damage the ozone layer, experts told Business Insider.
“This really shows how important basic research on the stratosphere is,” Daniel Murphy, a researcher at the National Oceanic and Atmospheric Administration's Institute of Chemical Sciences who led the particle study, told BI.
“There's something going on here that we didn't expect, and we don't fully understand the impact,” he said.
Particles in the stratosphere can form the ozone layer
Remember the ozone layer? If you lived in the 80's, you probably associated it with that era.
This important layer of the atmosphere, mostly contained in the stratosphere, protects us from ultraviolet radiation from the sun. About 40 years ago, when scientists warned that chlorofluorocarbons (CFCs) rising unchecked into the atmosphere were leaving a gaping hole in the pole, the topic was frequently in the headlines. I did.
The ozone hole doesn't make much news today. Thanks to the 1987 Montreal Protocol, a global agreement that set out to phase out gases harmful to the ozone layer, the ozone layer has been steadily recovering.
However, they are not gone. In September 2023, the hole above Antarctica grew to the sixth largest size ever observed, and then returned to normal. This is probably due to the effects of particles ejected by the 2022 eruption of the Hunga Tonga submarine volcano.
Therefore, it is important to keep an eye on stratospheric particles. These nanometer-sized debris arise naturally from meteors impacting the planet and can dramatically change the chemical makeup of the stratosphere.
Clouds do not usually form in the stratosphere because it is much drier than the troposphere, where most clouds form.
By incorporating elements not normally found in the sky, such as metals, these particles combine with sulfuric acid naturally present in the stratosphere, causing a chemical reaction that sucks in passing water vapor and creates ice crystals.
That could cause a chain reaction that could create rainbow-colored clouds in the polar stratosphere.
This spectacular cloud is harmless on its own, but when mixed with man-made gases it can become terrifying. The edge of the cloud provides the perfect conditions to convert harmful chlorine and bromide into their active, ozone-depleting forms.
Metals from satellites and spacecraft are evaporating into the atmosphere
Murphy and his colleagues recently conducted a study of stratospheric particle conditions over Alaska using a sensitive detector aboard NASA's High Altitude Research Vehicle WB-57.
The findings, published in October 2023 in the peer-reviewed journal PNAS, revealed that about 10% of the stratospheric sulfuric acid particles they picked up could not be explained by natural causes.
“We weren't actually looking for spacecraft, but the data showed that there were elements that couldn't possibly come from a meteor,” Murphy told BI.
The particles “have too much aluminum, too much lithium, and a few other elements to be coming from a meteor,” he said.
Murphy said two elements found in the particles were particularly surprising: niobium and hafnium.
These do not occur naturally and need to be improved, the scientists said.
“The combination of aluminum and copper, as well as niobium and hafnium used in high-performance, high-temperature alloys, suggested potential for the aerospace industry,” Murphy added.
At this point, we have no idea what these new particles can do. But scientists are hard at work trying to figure it out.
“This is an emerging problem, and we're just beginning to understand it,” Murphy said.
It may be possible to generate polar stratospheric clouds. If so, this could be a big problem in the short term, Martin Chipperfield, a professor of atmospheric science at the University of Leeds in the UK, told BI.
“Chlorine is decreasing so slowly that the timescale for the ozone hole to disappear is about 2060 years, based on current projections,” said Chipperfield, who was not involved in the study. .
“So even if we significantly increase space debris burnout over the next few decades, there is still plenty of room in the short term because the ozone hole will get worse before it gets better,” he said.
These new particles can also migrate into the troposphere, where they can influence the formation of feathery cirrus clouds. Unlike other clouds, cirrus clouds retain heat in the atmosphere, which can worsen the climate crisis.
The particles could also cause entirely new phenomena. Or maybe you can't do anything at all.
Their composition is unique, so it's unclear what to expect. Murphy said scientists need to perform experiments in the lab to verify this.
“The space industry is growing rapidly, so it's really important to understand that,” Murphy told BI.
“If there is an impact, it is better to understand it now before it grows, rather than after it has already grown significantly.”
we are realizing how little we know
Due to falling launch costs, the number of satellites orbiting the Earth is expected to increase from around 8,000 today to more than 50,000 by 2030. Many of these satellites are expected to have short lifetimes.
“If you multiply those numbers together, you end up with a satellite re-entering the atmosphere about once every hour on average,” Murphy said.
Murphy and his co-authors estimate that aerospace debris could account for 50% of stratospheric particles within the next few decades, further increasing the need to understand its impact. It is said that
Chipperfield said decommissioning the spacecraft is only part of the equation.
“Increasingly, rockets are being launched for small satellites and tourism purposes, burning kerosene and other fuels and emitting them into the atmosphere. Some satellites and orbits are then loaded with the possibility of returning to the atmosphere. “There's some fuel in there, like iodine, and then that disappears,” he said. He said.
“I think the whole life cycle of a satellite is definitely something to look at, and this burnup is part of that,” Chipperfield said.
Scientists are also seriously considering atmospheric environmental engineering to send billions of sulfuric acid particles into the stratosphere to protect Earth from the sun's heat.
For Murphy, this all goes to show how little we know about how humans are impacting the stratosphere as we take to the skies more and more.
“The fact that there were still surprises in our understanding of the composition of stratospheric particles is relevant to the discussion about adding more particles,” Murphy said.
