Nitrogen dioxide (NO₂)

A reddish-brown gas produced mainly by burning fuel — cars, power plants, and industry. Satellites map how much of it sits in the air below them.

Why it matters

NO₂ is a marker of combustion pollution, irritates lungs, and helps form smog and ground-level ozone, so its maps reveal traffic corridors, factories, and how air quality shifts with policy and the economy.

Where you’ll meet it

• TEMPO measures NO₂ hourly across North America during daylight, tracking pollution through the day.
• TROPOMI on Sentinel-5P maps global NO₂ at high resolution.
• OMI on Aura built the long-term global NO₂ record.

In plain terms

It’s like spotting the exhaust haze hanging over a busy highway from space — the more traffic and smokestacks below, the more NO₂ shows up.