At most, dust is seen as a nuisance for most people. However, its impact on the ecology of planet Earth has not yet been scientifically examined barring a few studies. NASA’s imaging spectroscopy technology seeks to chart these unknown territories as it measures the mineral composition of Earth’s arid land dust source regions.
What is already established is the fact that the arid land in northern Africa is the biggest source of dust in the world. NASA’s Earth Surface Mineral Dust Source Investigation (EMIT) mission, to be launched in June 2022, aims to deepen scientific understanding of fine particles of soil, silt, and clay from Earth’s deserts and, ultimately, how they affect climate.
A bulletin issued by the World Meteorological Organization (WMO) reported how mineral dusts impact weather as well as global and regional climate. While the aerosols absorb and scatters solar radiation entering Earth’s atmosphere, reducing the amount reaching the surface, and absorbs long-wave radiation bouncing back up from the surface, re-emitting it in all directions, they can also adversely impact human health, society, and the environment.
“Different kinds of dust have different properties – they’re acidic, they’re basic, they’re light-colored, they’re dark – that determine how the particles interact with Earth’s atmosphere, as well as its land, water, and organisms,” said Robert O. Green, EMIT’s principal investigator and a longtime researcher at NASA’s Jet Propulsion Laboratory in Southern California. With the EMIT data, he added, “we’ll be on track to map the world’s dust-source regions and understand how dust heats and cools the planet, as well as how that might change under future climate scenarios.”
EMIT is a state-of-the-art imaging spectrometer that will be aboard the International Space Station (ISS) to map the world’s mineral-dust sources, gather information about particle color and composition. It will focus on 10 important dust varieties.
“There is a lot of variability in the dust emissions – every second there’s some variability due to shifts in wind or rain, and there is seasonal, annual, and longer-term variability,” said Natalie Mahowald, EMIT’s deputy principal investigator and an Earth system scientist at Cornell University in Ithaca, New York.
EMIT’s spectrometer receives sunlight reflected from Earth, then divides it into hundreds of distinct colors and records it on a grid of light detectors. The grid has 1,280 columns, each with 480 elements, and every column is effectively its own spectrometer, reading the colors of a soccer-field-size patch of Earth’s surface. Together, the instrument’s detectors can scan a strip of land 50 miles (80 kilometers) wide, at a rate of more than 4.4 miles (7 kilometers) each second.
The above-mentioned bulletin by WMO lists surface dust deposits as a source of micro-nutrients for both continental and maritime ecosystems. It goes on to say that Saharan dust is thought to fertilize the Amazon rainforest, and dust transports of iron and phosphorus are known to benefit marine biomass production in parts of the oceans suffering from the shortage of such elements.
But it also lists negative impacts of dust on agriculture, quality of water in streams and rivers, transportation, and machinery. In fact, lack of data on dust composition means that it is still unclear whether dust particles cool the atmosphere or warm it.
Once EMIT begins operation, its data will be delivered to the NASA Land Processes Distributed Active Archive Center (DAAC) for use by other researchers and the public. EMIT is being developed at NASA’s Jet Propulsion Laboratory, which is managed for the agency by Caltech in Pasadena, California.
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