Just like radiant skin is considered a sign of good health in humans, plants also glow when they are well.
A potential new ESA satellite could use this fluorescence to track the health and productivity of vegetation worldwide.
The Florescence Explorer, or FLEX for short, is a candidate for ESA's eighth Earth Explorer. It aims to provide global maps of vegetation fluorescence, which can be used to work out actual photosynthetic activity.
This information would improve our understanding of the way carbon moves between plants and the atmosphere and how it affects the carbon and water cycles.
In addition, by offering new information that can be used to improve the management of water and fertilisers, FLEX could also improve agricultural productivity.
After the chlorophyll in a plant has absorbed sunlight, the core of the photosynthetic machinery gives off a red glow - fluorescence. This reflects how efficiently the plant is photosynthesising, or how well it is "breathing" and, therefore, how healthy it is.