Because Earth can sometimes look like an Impressionist painting from space, NASA added colours to the Mount Etna volcano eruption to separate what from what. The false-color image combines shortwave infrared, near-infrared and green light in the RGB channels. It looks like Earth on acid.
As you can imagine, the bright red in the image is scorching hot lava. The blue-green shows snow, the white is clouds and the green is the forest and other vegetation. NASA explains:
In the image, fresh lava is bright red, as the hot surface emits enough energy to saturate the instrument's shortwave infrared detectors but is dark in near-infrared and green light. Snow is blue-green because it absorbs shortwave infrared light, but reflects near-infrared and green light. Clouds made of water droplets (not ice crystals) reflect all three wavelengths of light similarly and appear white. Forests and other vegetation reflect near-infrared more strongly than shortwave infrared and green, and so appear green. Dark grey areas are lightly vegetated lava flows, 30 to 350 years old.
Without the added colour, the eruption would look like this from space:
Not so interesting anymore! Mount Etna has been at a low simmer for the past 10 months but exploded on February 19th to February 20th, with three outbursts in 36 hours. Volcanoes are better viewed from far, far away. [NASA via NPR]