This map shows a 2-month average of the abundance of nitrogen dioxide (NO2) in the air, as sensed from space by the new Sentinel-5P satellite from the European Space Agency.
Why it matters: The image, generated by scientists and data specialists at the space data analysis firm Descartes Labs, shows us the human footprint on the planet. "I find it fascinating that this image would be mostly blank if people weren't here burning stuff," says Tim Wallace, creative lead at Descartes Labs.
Nitrogen dioxide is part of a group of gases referred to as nitrogen oxides, or NOx. NOx is a key contributor to smog and a major health hazard, so monitoring it will help track its major sources.
"Whenever we're burning for either power production or transportation, anything that we’re burning is going to emit NOx," Laura Mazzaro, an atmospheric scientist and environmental engineer at Descartes Labs, tells Axios.
The big picture: NOx has a short atmospheric lifetime, on the scale of hours, so satellite sensors can give a near-real-time picture of combustion worldwide, from the cars leading to Los Angeles smog to biomass burning in the vast forests of Indonesia and South America.
"It affects people's quality of life directly," Mazzaro says.
A lot of point sources visible in the image are to be expected, such as major cities and oil production hubs. However, the hazy bands of NOx over the Amazon and sub-Saharan Africa may be clues to different sources of the compound, and interestingly, the satellite is even able to show typically used shipping routes.
Why you'll hear about this again: Mazzaro says the Sentinel satellite's capabilities could be used for monitoring compliance with environmental agreements, including air pollution reduction commitments on NOx, acid rain and any future regulations on methane pollution, given that it is a potent greenhouse gas that is on the increase.