The Earth is not a desert, but there are at least ten immense deserts on its surface. Their boundaries are not well-defined as they expand and contract, but mostly expand, under the watchful eyes of satellites. In the driest of them all, the Atacama Desert in Chile, not a drop of rain has fallen for at least four hundred years. They are packed in between the Tropic of Cancer and the Tropic of Capricorn, although they tend to escape those confines. Deserts cover tens of millions of square kilometres; a third of the Earth’s land surface comes under the scientific definition of desert. National borders are buried beneath their sand and rock. They separate, but also unite: the nine million square kilometres of the Sahara cover twelve nations. On the edge between environmental assets and liabilities, deserts are the sentries of climate change. Sadly, as James Lovelock, the father of the Gaia hypothesis, observed, it is much easier to create a desert than a forest. In the meantime, other planets are revealing their deserts: alien, and yet somehow familiar. Click here to download the Calendar (pdf)

Messak Plateau, Sahara Desert, Libya 24° 54’ N, 12° 12’ E Landsat-7 ETM+, courtesy Global Land Cover Facility     Taklamakan Desert, China 38° 41’ N, 79° 48’ E http://www.telespazio.com/calendar10/taklamakan.html Landsat-7 ETM+, courtesy Global Land Cover Facility     Date palm cultivations, El Oued, Sahara Desert, Algeria, 33° 27’ N, 6° 55’ E COSMO-SkyMed © ASI/Italian MoD     Solar energy plant, Mojave Desert, California, USA, 35° 01’ N, 117° 20’ O GeoEye-1 © GeoEye Inc. 2009     Darfur village, Sudan 14° 21’ N, 24° 25’ E GeoEye-1 © GeoEye Inc. 2009     Atacama Desert, Chile 24° 35’ S, 68° 59’ O Landsat-7 ETM+, courtesy Global Land Cover Facility     Click on the images to know more details