The new Copernicus Sentinel-4 mission has delivered its first images, highlighting concentrations of atmospheric nitrogen dioxide, sulphur dioxide and ozone. Despite being preliminary, these images mark a major milestone in Europe’s ability to monitor air quality all the way from geostationary orbit, 36 000 kilometres above Earth.
Earth has a long, 4.5 billion history full of momentous twists and turns. Multiple prominent events played leading roles in Earth's story. One of them is the catastrophic impact with another planetesimal early in Earth's history that not only created the Moon, but altered Earth's chemistry forever.

