This satellite image was captured over southeastern Algeria in the heart of the Sahara desert. The heat and lack of water render vast desert areas highly unwelcoming, making satellites the best way to observe and monitor these environments on a large scale. Satellites provide information on desert ecosystems and their expansion, and about areas at risk of soil degradation, erosion and desertification. Data from spaceborne sensors also assist in the water management of inhabited arid regions, and can track and help predict the movement of dust storms. Optical imagery of deserts from space is arguably the most fascinating: the diversity and untouched state of these landscapes produce unique and striking scenes. In this image, a large area of rock appearing purple stretches across the right side of the image, with fluvial erosion patterns testament to an earlier time when the area received more rainfall. Today, this area sees an average of about 10 mm of rainfall per year. Wind-shaped sand dunes are visible on the left. The area at the bottom appears to be flat, with tiny specks of vegetation. Just south of this image lies the Tassili n’Ajjer National Park and UNESCO World Heritage Site, renowned for its 10 000 year-old cave art. The drawings and engravings depict culture and the environment from a time when climatic conditions were more favourable to human occupation. Japan’s ALOS satellite recorded this image on 28 January 2011. ALOS was supported as a Third Party Mission, which means that ESA used its multimission ground systems to acquire, process, distribute and archive data from the satellite to its user community.