Space Perspective: Pollution Visible From Space?

The ability to observe Earth from space has provided invaluable insights into the planet's health and the impact of human activity. Among the pressing issues that can be monitored from space is air pollution, which the World Health Organization deemed the world's largest single environmental health risk in a 2014 report. NASA and other space agencies have employed a range of satellite technologies to track and measure air pollution, providing data that helps researchers, policymakers, and communities address this global challenge.

NASA's satellite technology, TEMPO, provides hourly observations of air pollution in North America

NASA's satellite technology has been instrumental in monitoring Earth's air pollution, which has been identified as the "world's largest single environmental health risk" by the World Health Organization. The space agency's fleet of Earth-observing satellites includes instruments that detect air pollutants worldwide, with data being utilised by researchers and air quality managers to understand the impact of air pollution on human health and agriculture.

Building on this, NASA's TEMPO (Tropospheric Emissions: Monitoring of Pollution) satellite technology is a significant advancement in air quality monitoring over North America. TEMPO is NASA's first Earth-observation satellite in geostationary orbit, providing hourly observations of air pollution across the continent. This high-frequency sampling is a notable improvement over previous satellites, which sampled air quality at lower levels, limiting their coverage to certain parts of the day.

TEMPO's geostationary orbit at 22,000 miles above Earth's equator allows it to remain fixed above the same point on the Earth's surface. This unique perspective enables it to capture hourly measurements of air pollution from sunrise to sunset, providing a comprehensive view of pollution throughout the day. The satellite's high resolution is another key advantage, enabling the collection of detailed data with a neighbourhood-scale focus.

The satellite technology observes primary pollution, which is directly emitted from vehicles and smokestacks, as well as secondary pollution, which is formed through chemical reactions in the atmosphere. TEMPO specifically monitors pollutants such as nitrogen dioxide, sulfur dioxide, ozone, and formaldehyde, all of which have significant impacts on public health.

By utilising TEMPO's data, scientists, air quality agencies, public health officials, and policymakers can gain valuable insights into the dynamics of air pollution. This information is crucial for addressing environmental justice issues, as it reveals disparities in pollution exposure between neighbourhoods, with lower-income areas often bearing the brunt of poor air quality due to their proximity to industrial sites.

Nitrogen Dioxide (NO2) is a harmful air pollutant, primarily produced by burning fossil fuels

NO2 is a highly reactive gas and has negative effects on human health. It is unhealthy to breathe and can irritate the airways in the human respiratory system, causing increased inflammation, worsened cough and wheezing, reduced lung function, and greater asthma attacks. Scientific studies suggest that exposure to NO2 may cause asthma in children and increase the risk of emergency department and hospital admissions. It also has adverse effects on pregnancy and birth outcomes and is potentially linked to an increased risk of kidney and neurological harm, autoimmune disorders, and cancer.

NO2 is a significant contributor to particle pollution and the formation of ground-level ozone (O3), which is also harmful to human health and negatively impacts plants, reducing crop yields. The dominant sources of NO2 are thermal power plants and automobiles, as they involve the combustion of fossil fuels.

NASA has employed a fleet of Earth-observing satellites to monitor air pollutants like NO2 around the world. The data collected by these satellites are used by air quality managers and researchers to study the impact of air pollution on human health and agriculture. The Tropospheric Emissions Monitoring of Pollution instrument (TEMPO) is a new satellite technology that will provide hourly observations of air quality in North America, offering a more comprehensive and accurate view of air pollution.

NASA satellites observed the impact of COVID-19 lockdowns on air pollution levels

Yes, pollution can be seen from space. NASA uses satellites to monitor Earth's air pollution, which has been deemed "the world's largest single environmental health risk" by the World Health Organization. These satellites observe air pollutants like nitrogen dioxide (NO2) and particulate matter (PM) around the world.

One such pollutant is PM 2.5, tiny airborne particles often produced by human activity that are about 30 times smaller than the width of a human hair. These particles are small enough to linger in the atmosphere and pose serious health risks when inhaled, including an increased risk of heart attack and cancer.

By combining NASA spacecraft data with ground-based monitoring and computer modeling, scientists mapped PM 2.5 levels across China, Europe, and North America during the early months of the pandemic. They found that seasonal differences in PM 2.5 between recent years were driven primarily by natural meteorological variability rather than pandemic lockdowns. The most significant lockdown-related differences were detected in China, specifically over the North China Plain, where the strictest lockdowns were in place.

In contrast, a gas pollutant known as nitrogen dioxide (NO2) did see dramatic declines during the lockdowns. NO2 is a major byproduct of fuel burning by vehicles, and its decline was visible from space and the ground. Images of clear, blue skies in places once shrouded by heavy smog flooded popular news and social media, suggesting that COVID-19 had drastically reduced all types of pollution.

However, the relationship between NO2 and PM 2.5 is not linear. Half as much NO2 in the atmosphere does not necessarily lead to half as much PM 2.5 produced by NO2. PM 2.5 often comes from similar sources as NO2, so researchers questioned whether the lockdowns resulted in a decline in PM 2.5 levels.

To investigate this further, the team led by Melanie Hammer at Washington University in St. Louis compared monthly estimates of PM 2.5 levels from January to April in 2018, 2019, and 2020. They found that the most significant lockdown-related differences were in China, specifically the North China Plain, where strict lockdowns were implemented. To confirm that the lockdown was responsible for the decrease in PM 2.5, the team ran "sensitivity simulations" using a chemical transport model.

The findings of this study highlight the complexity of tackling PM 2.5 pollution, which has multiple sources beyond just transportation emissions. The research also underscores the importance of satellite data in providing a global perspective on air quality, especially in regions without extensive ground monitoring systems.

The ESA is exploring how satellites can help tackle ocean plastic pollution

The European Space Agency (ESA) is exploring how satellites can help tackle the pressing issue of ocean plastic pollution. Around 10 million tonnes of plastic waste enter the oceans annually, threatening the health of marine life, humans, and the planet. While it is easy to see plastic waste washed up on beaches, litter can also be found far out at sea and has even been discovered in frozen polar ice.

The ESA is currently funding 26 innovative projects that are mapping the direction of satellite usage in detecting and tracking ocean plastic. Satellites can be pivotal in tackling this enormous environmental problem in several ways. Firstly, they can spot build-ups of marine litter by observing infrared light reflected by the litter and looking for a "fingerprint" that indicates the presence of plastic. This technology is already used in recycling factories to sort plastics. Secondly, satellite maps of ocean currents are used to predict litter accumulation in the Pacific, Atlantic, and Indian Oceans. By combining these two methods, scientists can create accurate maps of ocean plastic pollution, helping to understand the true scope of the problem and enabling the formulation of effective solutions.

Additionally, the ESA has launched spacecraft like the Sentinels, which orbit the Earth, capturing images and data for scientists. This information is used to monitor water levels, prepare for floods, and ensure adequate water availability. The Sentinel satellites are aptly named after soldiers who watch out for danger, as they keep a vigilant eye on our planet.

The use of satellites to monitor pollution is not limited to plastic waste in oceans. NASA, for example, employs a fleet of Earth-observing satellites to monitor air and water pollution. These satellites observe air pollutants like nitrogen dioxide (NO2), ozone (O3), and particulate matter (PM), providing data that helps air quality managers and researchers studying the health and agricultural impacts of pollution. Furthermore, new satellite technology called "TEMPO" will provide hourly observations of air quality in North America, offering a more comprehensive view of air pollution throughout the day and at a neighborhood-level scale.

Burning space junk in the Earth's atmosphere creates air pollution that can affect climate change

It is possible to see air pollution from space, and NASA has a fleet of Earth-observing satellites that do just that. These satellites can observe the planet's oceans, biosphere, and atmosphere, collecting data on air pollutants that is then used by researchers and air quality managers. NASA's satellites have also been used to monitor the impact of COVID-19 lockdowns on air pollution levels.

Now, turning to the issue of space junk, the burning of this debris in the Earth's atmosphere has been found to create air pollution that can affect climate change. Scientists have long suspected that the burning of space junk in the Earth's atmosphere could lead to air pollution, and recent research has confirmed the presence of these pollutants in the stratosphere. This is the second-lowest layer of the Earth's atmosphere, extending from about 6 to 30 miles (10 to 50 kilometers) above the planet's surface.

Using high-altitude NASA aircraft, researchers detected traces of lithium, aluminum, copper, and lead in the stratosphere. The concentrations of these pollutants were much higher than what could be attributed to natural sources, such as the evaporation of cosmic dust or meteorites upon entering the atmosphere. Instead, the ratios of these chemical compounds matched those found in alloys used in satellite manufacturing.

The presence of these pollutants in the stratosphere is concerning because it is the atmospheric region that contains the Earth's protective ozone layer. Aluminum oxide, a product of burning aluminum-based alloys, is known for its ability to destroy ozone. Additionally, high concentrations of aluminum oxides can alter the Earth's albedo, or its ability to reflect light, which could lead to unforeseen temperature changes in the stratosphere and potential consequences for the planet's climate.

The rise of space tourism and the increasing number of rocket launches and satellite re-entries are expected to exacerbate this issue. With the proliferation of satellite mega-constellations, such as SpaceX's Starlink, the number of satellites launched into orbit is projected to increase sharply in the coming years, resulting in a corresponding rise in satellite re-entries and the burn-up of chemical compounds in the upper atmosphere.

While the ultimate impacts of spacecraft-sourced metals on the Earth's climate and habitability are still uncertain, it is clear that this form of metallic pollution will intensify as space activity increases.

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