The 22 March is World Water Day, which focuses on the importance of freshwater. The Sustainable Development Goals of the United Nations aim to achieve a better and more sustainable future.
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.
From an altitude of 225 nautical miles, one of the Expedition 40 crew members aboard the International Space Station was looking almost straight down when he photographed this picture of Lake Chad.