In a memorable chronicle, Gabriel Garcia Marquez He confessed, “without shame and even with a certain macho pride,” his fear of flying. Like this: “Perhaps because it is a different fear, one that has not existed since our origins, like the fear of the dark or the fear itself of being perceived as being afraid. On the contrary: the fear of flying is the most recent of all, since it has existed since the science of flying was invented.” An even more contemporary fear is that objects from space fall on our heads. It is worth remembering the panic caused in 1979, when the Skylab space stationalready empty of astronauts, disintegrated upon re-entering the Earth’s atmosphere.
What would become of those 91 tons of steel? The possibility that a piece, no matter how small, would reach a person was relevant; according to mathematical calculations, the pieces spread like viruses: one in 152. The possibility that it would reach a city of 100,000 inhabitants was one in seven. There was immense panic, despite the calm requested by the POT (the United States space agency), but the debris fell over the Indian Ocean and desert areas of Australia. The remains are now in museums.
Concern about what comes from space, however, did not stop there, with the Skylab misfortune, and has been the subject of new studies by international organizations that catalog space debris. There is millions of rubble, yes, from different origins. The problem grew at an accelerated pace, as a result of the space race and the entry on the scene of countries such as India, Japan and the United Arab Emirates, as well as private companies: SpaceX and Blue Origin.
With these new players launching devices through the sky, it is natural that the dirt will multiply. It’s clear: the more satellites sent into space, the greater the chance that objects will wander across the sky and get lost. Of the 15,000 probes placed in orbit since the beginning of space exploration, 7,500 remain operational around the world. In other words, half became floating trash, without any function. There is a tiny, almost zero, risk of hurting real people. However, contact with other machines is much more likely. From known and tracked space debris, 70 percent are in low Earth orbit, which extends approximately 2,000 kilometers above the Earth’s surface.
When turned off, these devices are pulled downward by the Earth’s gravitational force. They burn up upon returning to Earth’s atmosphere, but do not disappear completely. There are pieces left, but only the largest ones, measuring more than 10 centimeters, are cataloged and can be traced. Some objects are huge, the size of a school bus, like the Envisat satellite, launched in 2002 by the European Space Agency (ESA) and deactivated ten years later. With an unknown trajectory, smaller debris is also dangerous, because it can destroy spacecraft as a result of the speed it reaches.
Scope of space debris
To better measure the extent of the impact of space debris, a U.S. team of scientists from the National Oceanic and Atmospheric Administration (NOAA) recently analyzed air samples from the stratosphere and noted the presence of more than twenty types of metal particles: silver, nickel and aluminum, used in the construction of rockets and satellites. Bliss variety of metals comes from satellites and rocket boosters spent vaporized by the intense heat they receive when they re-enter the Earth’s atmosphere.
Metal dust does not directly contaminate the lower layers of the atmosphere nor does it negatively interfere with the quality of the air you breathe, which is already degraded. However, there is a risk of interference with the ozone layer, a natural protective shield against global warming. “There could be some damage to people’s health,” explains Daniel Murphy, who led a team that included scientists from CIRES, Purdue and the University of Leeds.
The discovery is one of the initial findings from the analysis of data collected by a high-altitude research plane over the Arctic during a NOAA Chemical Sciences Laboratory mission called SABER, abbreviation for stratospheric aerosol processes, budget and radiative effects. It is the agency’s most ambitious and intensive effort to date to investigate aerosol particles in the stratosphere, a layer of the atmosphere that moderates Earth’s climate and houses the protective ozone layer.
Using a custom-built instrument at NOAA in Boulder, Colorado, and mounted in the nose of a NASA WB-57 research plane, scientists found aluminum and exotic metals embedded in about 10 percent of the particles. of sulfuric acid, which constitute the vast majority of particles in the stratosphere. They were also able to compare the proportion of rare elements they measured with special alloys used in rockets and satellites, thus confirming their origin as vaporized metal from spacecraft re-entering the Earth’s atmosphere. The research findings were published in the prestigious journal Proceedings of the National Academy of Sciences (PNAS).
“Two of the most surprising elements we saw in these particles were niobium and hafnium,” explains Daniel Murphy. “They are both rare elements that are not expected in the stratosphere. It was a mystery where these metals come from and how they end up there.”
Pioneer, SABER mission
The SABER mission focused on aerosols, small particles that absorb and reflect the Sun’s rays, shielding the Earth and that, under the right conditions, serve as surfaces for chemical reactions that destroy the ozone layer. It is the first time that research directly links stratospheric pollution to the re-entry of space debris.
Niobium and hafnium are not found as free elements in nature, but are refined from minerals. They are used in semiconductors and super alloys. In addition to these two unusual elements, a significant number of particles contained copper, lithium and aluminum in concentrations much higher than those found in meteorites or “space dust.” “The combination of aluminum and copper, plus niobium and hafnium, which are used in high-performance, heat-resistant alloys, drew us to the aerospace industry,” Murphy said.
In total, scientists identified more than 20 different elements from spacecraft and satellite reentry in the particles sampled during SABER, including silver, iron, lead, magnesium, titanium, beryllium, chromium, nickel, zinc and lithium.
NOAA scientists were able to accurately identify so many different metals thanks to a custom instrument called PALMS (for Particle Analysis by Laser Spectrometry) that analyzes the chemical composition of individual particles in the air one by one while the plane is in flight.
Scientists are eager to understand how these aerospace debris particles interact with other aerosols in the stratosphere due to the expected increase in space traffic and its potential impact on the ozone layer. They also want to explore the impact of possible future proposals to seed the stratosphere with millions of tonnes of sulfur aerosols to slow the pace of global warming by reflecting sunlight back into space.
“At 10%, the current fraction of stratospheric aerosols with metallic nuclei is not large,” study co-author Martin Ross told The Aerospace Corporation. “But in the last five years more than 5,000 satellites have been launched. “Most of them will return in the next five years and we need to know how this could further affect stratospheric aerosols.”
In 1996, a fragment from the disintegration of a rocket caused damage to a French military satellite installed 660 kilometers from Earth. Spacewalks around the International Space Station (ISS) were interrupted due to contact with debris in orbit. Therefore, regulating space exploration to stop pollution is the best way to prevent the cosmos from becoming a hostile environment.
