When you’re working in the yard this summer, take a look up: Using a satellite, NASA scientists are paying attention to how healthy your lawn and garden are.
Next month, the agency plans to launch the Orbiting Carbon Observatory-2. Its primary aim is to create a global map of carbon sources and carbon sinks. The OCO-2 mission will provide the most detailed map of photosynthetic fluorescence — that is to say, of how plants glow — ever created. Using this data, scientists should be able to estimate how quickly the world’s plants are absorbing carbon from the atmosphere.
The applications of the project are wide-ranging, but the science is easy enough to understand. During photosynthesis, a plant absorbs light, then re-emits it at a different wavelength. This is known as fluorescence. Botanists can measure the intensity of fluorescence to estimate how actively a plant is photosynthesizing. A satellite could, in theory, detect the light emitted by the world’s plants to estimate how much carbon the plants are absorbing. But there has always been a big, fiery problem: the sun.
There are huge swaths of the universe that we simply cannot see because the brightness of the sun obscures our view. In much the same way, the sun was thought to make it impossible to measure global photosynthetic fluorescence. The sun’s broad-spectrum rays were presumed to overwhelm the wavelengths of plant fluorescence, making them virtually impossible to detect.
That’s where NASA’s Joanna Joiner of the Goddard Space Flight Center in Greenbelt, Md., and Christian Frankenberg of the Jet Propulsion Laboratory in Pasadena, Calif., came in, with their innovative use of an electromagnetic phenomenon known as Fraunhofer lines. In the early 19th century, German optician Joseph Fraunhofer noticed that, in between the bands of colored light that emerged from a prism, several dark lines appeared. That’s because, by the time sunlight reaches Earth, molecules in the atmosphere have absorbed certain wavelengths of light. In other words, our atmosphere blocks out the sun in certain wavelength bands of the electromagnetic spectrum. Joiner and Frankenberg realized that they could look for plant fluorescence in the bands where the sun’s light has been dimmed.
A detailed map of photosynthetic activity and carbon absorption will better inform conservation efforts, possibly serving as an early warning system and highlighting when and where to focus such efforts.
Managing a garden from space sounds a bit futuristic, but horticulture is about to enter the Space Age. From now on, you’re not just trying to impress the neighbors with your green thumb.