This Envisat image over the North Sea captures numerous aircraft condensation trails, or 'contrails', as well as parts of the Netherlands (upper right), Belgium (lower right) and England (lower left).
Exhaust emissions from jet aircraft contain large amounts of water vapour which, under certain atmospheric states, will condense to form ice crystals.
These act as condensation nuclei around which even more water vapour in the surrounding air condenses. The end result is the formation of an elongated cloud-like condensation trail in the sky.
Contrails can last anywhere from a few minutes to hours. They can also grow to form persistent artificial cirrus clouds that can last for days or weeks. Contrails and cirrus clouds could potentially have an impact on Earth’s climate by trapping the Earth's heat in our atmosphere in a similar way to greenhouse gases.
The various colours of green visible in the sea are due to sediments transported in the water.
This image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on 21 March 2009, working in Full Resolution mode to provide a spatial resolution of 300 m.