The plume of ash from Iceland's Eyjafjallajoekull volcano shows brown among the clouds as it is blown across Europe in this Envisat image from 6 May 2010.
At this stage in the eruption, the ash cloud stretched 1600km across the Atlantic Ocean, travelling first east and then south in the prevailing winds. The volcano began emitting steam and ash on 20 March 2010.
Envisat was launched into a polar orbit in 2002 in order to monitor environmental and climate changes. It is a joint mission of the European Space Agency and Canada and carries a range of instruments including synthetic aperture radar, radiometers, spectrometers and an altimeter. This image comes from the Medium Resolution Imaging Spectrometer (MERIS).