Recently tweeted from the International Space Station, this image of the extremely arid West African coast of the Atlantic Ocean looks otherworldly. The image shows 215 kilometers (134 miles) of the Saharan coastline. The main patterns seen from orbit are the straight lines produced by strong northerly winds that blow parallel to the coast, producing wind streaks of sand and sand-free surfaces.
The Sun’s rays are reflected off salty lagoons known as sabkhas near the coast. Reflected sunlight (sunglint) also highlights wave features on the ocean in the upper right corner of the image. Known as internal waves, the waves move in groups towards the coastline. Surface waves are responsible for the ocean’s green tint on the left. The waves erode the coastline, and the resulting sediment colors the water.
The bright straight line at image lower left is a transport corridor of roads, railroads and conveyor belt systems that transport phosphates 100 km (60 miles) from inland mines to the coast. Strong northerly winds blow dust and phosphate into the desert, giving a jagged edge to this line on its south side. The features in this image—unfamiliar to many—are common in other west coast deserts such as the Namib Desert of Namibia and the Atacama Desert of Chile and Peru.
Astronaut photograph ISS040-E-788 was acquired on May 20, 2014, with a Nikon D3S digital camera using a 80 mm 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 the Expedition 40 crew The image in this article has been enhanced to improve contrast. 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, Jacobs at NASA-JSC.