We don't hear too much about natural dust, the kind that the winds loft from deserts and dry lakebeds into the air and carries for hundreds of kilometers, crossing oceans and continents, but we should. Plumes of dust connect the atmosphere, the oceans and the forests, and affect the most fundamental processes of life on our planet. Scientists believe that dust has profound and somewhat mysterious influences on atmospheric chemistry, solar heat exchange and nutrient supply to the oceans and rain forests. What those influences are, exactly, is the subject of much study and is still somewhat mysterious--the story of dust shows just how complex our natural world is, and how difficult it is to understand it. For more, see our February feature story, 'Swept From Africa to the Amazon'.
Here are some spectacular natural-color images of dust storms taken by NASA's Aqua satellite, which was launched on May 4, 2002. The images were all taken with an instrument called the Moderate Resolution Imaging Spectroradiometer MODIS, one of six aboard Aqua.
Cloud free skies on November 27, 2011 gave a clear view of dust storms over Baja, California and the Pacific coast of Mexico. The Ocean Color Team at NASA's Goddard lab uses these images for asses sediment and plankton levels in the ocean. The dust helps fertilize the waters with nutrients that promote phytoplankton blooms. In winter, the waters around Baja are often full of whales, which eat the plankton.
This image is a close up of the November 27, 2011 dust plume blowing off mainland Mexico over the Gulf of California. The dust apparently rose over the desert of Sonora, not shown.
That tan finger stretching north hundreds of miles across the Mediterranean Sea from just west of the Nile Delta to east of Crete is a plume of dust, most likely from desert regions of Egypt and Libya. The image was captured on February 23, 2011.
Dust blows off the southern shores of Oman in the Arabian Peninsula, across the Gulf of Oman, to the east coast of Pakistan, on March 30, 2011.
In the afternoon of May 26, 2011, dust crosses the Red Sea.
Two dust plumes blow southeastward through Iraq on June 19, 2011. The western plume, which blows over the border with Kuwait, probably arose from dry lake or riverbeds, which accounts for its beige color. The eastern, darker plume arose in southeastern Iraq and blows toward the Persian Gulf.
Dust plumes blow off the west coast of Africa and over the Atlantic Ocean in this image, captured in late September 2011. The dust plumes have a wave-like appearance, with bands of thick dust alternating with bands of relatively clear air. The plume appears to be headed towards Cape Verde, to the southwest.
Dust blows south-southwest about 100 kilometeres over the Gulf of Alaska in this early November 2011 image. It arose in the Copper River Valley, which zigzags through the Chugach Mountains. Glaciers grind bedrock into a powder, with a consistency similar to flour, which is lifted into the air by winds. The swirls of iridescent green in the waters along the shore are probably sediment and phytoplankton.
Dust plumes blow off the coast of Morocco, toward the north-northwest, just missing Lanzarote, the easternmost of the Canary Islands. A skinny cloud bank runs almost perpendicular to the dust plumes. This image was captured on December 29, 2010.
A large dust storm sweeps across the North China Plain, over the Yellow Sea towards the Korean Peninsula in this March 12, 2010 image. A bank of clouds, probably from the same weather system that caused the dust storm, frames the northern edge. The dust appears to come from somewhere to the west. The haze in the southwest portion of the image may contain dust, but it is likely smoke from widespread fires in Southeast Asia.