This east-looking photograph, taken by astronauts from the International Space Station, shows the arid landscapes of the Sahara and the darker vegetation of the wetter, semi-arid woodland known as the Sahel.
The dark green marshes of Lake Chad stand out in the foreground. Even though it is more than 200 kilometers (120 miles) long, modern Lake Chad is just a small remnant of a vast lake that has repeatedly occupied the most of this landscape in the recent geological past. This lake basin stretches almost 1000 kilometers (600 miles) from the foreground of the image to the foot of the Tibesti Mountains. The lowest slopes of the Tibesti show the remnants of great deltas.
The image also captures an active dust plume, though it is partly obscured by the “Canada Arm” of the Space Station. The dust rises from the white mud flats of the ancient lake bed, likely from the Bodele Depression. Lofted into the atmosphere by northeasterly winds, dust from this basin often reaches the Atlantic Ocean, which is thousands of kilometers to the west. Occasionally this dust is even carried by weather systems as far as the Americas.
Astronaut photograph ISS042-E-244403 was acquired on February 12, 2015, with a Nikon D4 digital camera using a 32 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by a member of the Expedition 42 crew. The image has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by M. Justin Wilkinson, Texas State University, Jacobs Contract at NASA-JSC.