Strong winds lift mineral dust from Earth’s desert and dryland regions and carry the dust particles great distances. Depending on its color and composition, mineral dust can affect Earth’s environment in different ways. Dark particles absorb sunlight and heat our planet, while light-colored particles can have a cooling effect.

Minerals containing iron tend to be dark, and those with clay tend to be lighter in color. To improve global science models and understand how dust heats and cools the Earth’s environment, scientists need to know the dust’s mineral composition as it blows around Earth.

For the first time, the NASA Earth Surface Mineral Dust Source Investigation (EMIT) mission will comprehensively measure the mineral composition of Earth’s dust source regions to help scientists understand how they heat or cool our planet. EMIT’s science objectives are specifically focused on better understanding this heating and cooling effect, which is called radiative forcing. The first objective is to deliver a new improved assessment of the heating and cooling effects of mineral dust in the Earth’s atmosphere. The second objective is to predict how future climate scenarios might change the amount and type of mineral dust emitted into the Earth’s atmosphere.

data visualization
One of NASA’s airborne missions has been used to test EMIT’s spectroscopic approach to mapping mineral composition. In the Salton Sea region of California, the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument collected the large data set in the figure below. By obtaining a spectrum for every point in the image, AVIRIS successfully mapped the minerals hematite, goethite, calcite, and kaolinite based on their distinct spectral signatures. These are key minerals for the EMIT investigation.

To achieve these objectives, EMIT will use imaging spectroscopy, an advanced technology invented by NASA, and widely used in the agency’s space missions. For each location in an image, EMIT will measure the spectrum of light — ranging from visible into the infrared — reflecting from Earth’s surface. The measurements will reveal distinct spectral signatures (or ‘fingerprints’) of the minerals in dust source regions. Scientists will then use those observations to generate new, more accurate mineral composition maps of Earth’s dust source regions.

EMIT observation chart
The EMIT science team will use the mission’s new maps to initialize advanced Earth System Models. The updated models will help scientists better understand the effect of mineral dust composition, and allow them to reduce uncertainty in dust-related heating and cooling effects on Earth. Researchers will also run the models for future climate scenarios to assess how dust sources could change, which will help them understand how dust’s heating and cooling effects might change as well.
EMIT global picture
Model runs of these ESMs initialized with EMIT measurements will be used to assess and update of current and future predicted radiative forcing to achieve the EMIT science objectives. An example of current assessment of radiative forcing from mineral dust aerosols is shown below.

EMIT is a NASA Earth Venture Instrument investigation focused on achieving its two objectives. But the mission is also committed to ensuring that its measurements are made available for the additional science and applications that they will enable. All EMIT measurements and data products will be made available publicly through the NASA Land Processes Distributed Active Archive Center.

Now in development, the EMIT instrument builds upon NASA’s long history of developing advanced imaging spectrometers for new science and applications. EMIT is planned to launch to the International Space Station (ISS) in the year 2022.