Measuring dust on Earth from space

  The instrument for NASA’s Earth Surface Mineral Dust Source Investigation (EMIT) mission launches in July 2022. EMIT itself is not a spacecraft, but an instrument mounted on the International Space Station. Its main purpose is to study dust in Earth’s atmosphere, which is blown up by winds in arid regions and carried around the globe. Dust affects the globe, adversely affecting human health. The researchers hope to use EMIT to understand where the dust comes from, what it’s made of, and, in turn, what role dust plays in influencing climate.
  EMIT’s spectrometer takes sunlight reflected from Earth and separates it into hundreds of different colors, which are eventually recorded on a grid of light detectors. The grid has 1,280 columns, each with 480 elements, and each column is effectively its own spectrometer, responsible for reading the color of an area the size of a football field on the Earth’s surface. Because each type of dust has a unique light-reflecting signature, researchers use it to determine the mineral and chemical composition of material on Earth’s surface. The precision of these observations makes EMIT’s instrument one of the most complex Earth-facing imaging spectrometers ever sent into space.

Space Mineral Map of Southwestern Libya in the Sahara Desert

  This state-of-the-art imaging spectrometer can be used to map the source of mineral dust, gathering information on particle color and composition while the instrument is operating over dry, sparsely vegetated areas. EMIT is known to focus on 10 important dust species. Darker, iron-rich dust absorbs heat from the sun, warming the air around it; lighter, clay-rich particles do the opposite. With EMIT data, researchers can map the world’s dust source regions and understand how dust heats and cools the Earth, and how that might change under future climate conditions.
  The front of the stereo image in this article shows the color view of the southwestern Libya region as observed by the EMIT Imaging Spectrometer. The profile depicts an area about 800 kilometers south of the Libyan capital Tripoli.
  Analysis of the patterns showed that the surface of the area contained kaolinite, a light-colored clay mineral, and two darker iron oxide species — goethite and hematite. When dust from areas dominated by kaolinite is thrown into the atmosphere, the particles tend to scatter sunlight and reflect it back into space, cooling the air. Iron oxide particles in the air have the opposite effect, they tend to absorb heat and heat the surrounding air.