The USGS Landsat archive has over 3 million images from around the globe and spans over 4 decades. The products displayed in this service are 3-band composites called LandsatLook. These data cannot be used for rigorous scientific analysis, but are intended for visual interpretation and education. For more information on LandsatLook products, please visit: http://landsat.usgs.gov/LandsatLookImages.php. For more information about full Landsat data products, resolutions, map projection and so forth, please visit: http://landsat.usgs.gov/Landsat_Processing_Details.php.