Using Satellites to Precisely Measure Plant Health from Space
During photosynthesis, plants emit fluorescence - light invisible to the naked eye but detectable by satellites orbiting above Earth. NASA scientists have established a method to turn this satellite data into global maps of the subtle phenomenon in more detail than ever before. The new maps, produced at NASA's Goddard Space Flight Center, have a 16-fold increase in spatial resolution and a three-fold increase in temporal resolution over the first proof-of-concept maps released in 2011. The new maps were possible due to the development of a way to identify the very faint fluorescence signal collected by the Global Ozone Monitoring Instrument 2 (GOME-2) instrument on Metop-A, a European meteorological satellite. Fluorescence measurements like these are important because they can be used to develop improved vegetation models, and this will lead to better predictions of how plants will interact with the Earth's environment in a changing climate.
Transcript
00:00:08 Light gives plants the energy they need to grow. But what happens if plants receive too much light? The answer is they glow. This neon glow is actually happening around us all the time. The result of a cellular process where light from the sun is transformed and released as fluorescent light.
00:00:33 A journey into the plant cell reveals how it works. This is a chloroplast, the energy producing organ found inside the cells of plants. When sunlight strikes a plant, disc-like structures within the chloroplast absorb the light and convert it into energy. However, a small fraction of this light, about one percent, is emitted as fluorescent light. The light exits the plant cell and is released into the atmosphere.
00:01:11 The amount of light released can vary depending on factors like the time of day, time of year, and how much sunlight is being absorbed. Humans can't see this light. Our eyes just aren't that sensitive. To see the fluorescent light that's emitted from plants all over the world, we have to use scientific instruments that are placed on satellites. Earth observation satellites outfitted with special sensors are able to detect this light from space. After multiple orbits, scientists can construct a detailed view of the data.
00:01:48 This is what plant fluorescence looks like on a global scale. The visualization was created from five years of satellite measurements analyzed by a team of researchers led by scientists at NASA's Goddard Space Flight Center. Each point of light on this globe represents fluorescent light exiting a plant cell. The greater the intensity of light, the brighter the color. By observing changes in intensity over time, scientists can distinguish stressed, dead or dormant plants from healthy and growing vegetation.
00:02:27 Fluorescent measurements like these are important because they can be used to develop improved vegetation models. And this will lead to better predictions of how plants will interact with the Earth's environment in a changing climate.