Plants grow and thrive through photosynthesis, a process that converts sunlight into energy. During photosynthesis, plants emit what is called fluorescence – light invisible to the naked eye but detectable by satellites orbiting hundreds of miles above Earth. NASA scientists have now established a method to turn this satellite data into global maps of the subtle phenomenon in more detail than ever before.
Machinery inside the chloroplasts of plant cells converts sunlight to energy, emitting fluorescence in the process. Scientists can detect the fluorescence fingerprint in satellite data.
Image Credit: NASA Goddard's Conceptual Image Lab/T. Chase
Healthy plants use the energy from sunlight to perform photosynthesis, and re-emit some of that light as a faint but measureable glow. In short, abundant fluorescence indicates active photosynthesis and a well functioning plant, while low or no fluorescence can mean that the plant is stressed or shutting down. Maps of the phenomenon give scientists a direct look at plant health.
The new maps – produced by Joanna Joiner of NASA's Goddard Space Flight Center in Greenbelt, Md., and colleagues – boast 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 from a different satellite instrument. Improved global measurements could have implications for farmers interested in early indications of crop stress and ecologists looking to better understand global vegetation and carbon cycle processes.
"For the first time, we are able to globally map changes in fluorescence over the course of a single month," Joiner said. "This lets us use fluorescence to observe, for example, variation in the length of the growing season."
Vegetation dynamics, including the northward migration of plant growth during the northern hemisphere springtime, is already observed indirectly by satellite data used measure the "greenness" of light reflected from Earth's surface. Fluorescence measurements complement the greenness measurements by providing direct and immediate information about plant productivity. For example, the researchers saw plants start to shut down in the fall before their leaves turned colors. They also clearly detected early plant growth during the warm spring of 2012.
The maps were possible due to the development of a new 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. Acquiring the measurement is complicated by the fluorescence signal mixing with that of sunlight reflected from Earth's surface and clouds, and the absorption of sunlight by gases in the atmosphere.
To identify fluorescence, Joiner and colleagues took advantage of that fact that each of these signals has its own unique spectral signature akin to a fingerprint – whether from fluorescence, Earth's surface or the atmosphere. Match the fingerprint associated with fluorescence and scientists can tease out that data from the rest of the light.
Detangling the signal from atmospheric influences was a complexity not present in the pioneering research in 2011, when Joiner and colleagues produced the first global maps that proved the concept of measuring global land plant fluorescence from space. That study relied on data from a spectrometer aboard a Japanese satellite called the Greenhouse Gases Observing Satellite (GOSAT). Researchers analyzed an unusually dark section of the infrared portion of the solar spectrum where there is little background light, making it possible to distinguish the faint fluorescence signal.
Despite its complexities, the new method allows for more frequent measurements capable of producing higher resolution maps. Previous observations with GOSAT relied on averaging the data over areas of 200 square kilometers every month. Now, with GOME-2, scientists average the data over areas of just 50 square kilometers about every 10 days. The study was published online for review in April in Atmospheric Measurement Techniques.
"The more precise and more frequent sampling is valuable, allowing us to zoom in on the regions with the highest fluorescence signals," Joiner said. "Our data indicate that agricultural areas in the U.S. Midwest are some of the most productive lands on Earth. We can also now correlate our satellite fluorescence measurements with tower-based observations of carbon dioxide taken up by plants."
The research also paves the path for fluorescence studies based on measurements from future atmospheric or fluorescent-specific observations. Such observations could come from NASA's Orbiting Carbon Observatory-2, a mission designed to measure carbon dioxide that will launch no sooner than July 2014, and the European Space Agency's Fluorescence Explorer mission, which could be selected in 2015 for launch toward the end of the decade.Kathryn Hansen
Kathryn Hansen | EurekAlert!
Observations of nearby supernova and associated jet cocoon provide new insights on gamma-ray bursts
18.01.2019 | George Washington University
A new twist on a mesmerizing story
17.01.2019 | ETH Zurich Department of Physics
The scientific and political community alike stress the importance of German Antarctic research
Joint Press Release from the BMBF and AWI
The Antarctic is a frigid continent south of the Antarctic Circle, where researchers are the only inhabitants. Despite the hostile conditions, here the Alfred...
World first experiments on sensor that may revolutionise everything from medical devices to unmanned vehicles
The new sensor - capable of detecting vibrations of living cells - may revolutionise everything from medical devices to unmanned vehicles.
Dead and alive at the same time? Researchers at the Max Planck Institute of Quantum Optics have implemented Erwin Schrödinger’s paradoxical gedanken experiment employing an entangled atom-light state.
In 1935 Erwin Schrödinger formulated a thought experiment designed to capture the paradoxical nature of quantum physics. The crucial element of this gedanken...
Cellulose obtained from wood has amazing material properties. Empa researchers are now equipping the biodegradable material with additional functionalities to produce implants for cartilage diseases using 3D printing.
It all starts with an ear. Empa researcher Michael Hausmann removes the object shaped like a human ear from the 3D printer and explains:
The phenomenon of so-called superlubricity is known, but so far the explanation at the atomic level has been missing: for example, how does extremely low friction occur in bearings? Researchers from the Fraunhofer Institutes IWM and IWS jointly deciphered a universal mechanism of superlubricity for certain diamond-like carbon layers in combination with organic lubricants. Based on this knowledge, it is now possible to formulate design rules for supra lubricating layer-lubricant combinations. The results are presented in an article in Nature Communications, volume 10.
One of the most important prerequisites for sustainable and environmentally friendly mobility is minimizing friction. Research and industry have been dedicated...
16.01.2019 | Event News
14.01.2019 | Event News
12.12.2018 | Event News
18.01.2019 | Materials Sciences
18.01.2019 | Life Sciences
18.01.2019 | Health and Medicine