it's genuine
The photo's been making the rounds since 2005, long enough to make it into the snopes.com urban legend site, where it's listed as genuine. It's a National Geographic cover photo by photographer George Steinmetz, who, it's reported, flies a motorized paraglider over the desert to take photos like that. It's offered for download as wallpaper from NatGeo, and there's a larger version available, and though it has more detail, the shadows remain just as sharp, just as "painted on". I find it remarkable and beautiful image.