The image is from [1] ("Blue Marble: Land Surface, Shallow Water, and Shaded Topography ", 2002). I took the two 21600x21600 images, land_shallow_topo_west.tif and land_shallow_topo_east.tif, and composed them. I cropped the resulting image at 8460x8900+19400+6200.

Regarding the source data of the original, NASA-Blue Marble file, it is being explained [2] that it

• used a set of satellite-based observations to yield an image with 1 km² (0.386 square mile) resolution
• most information comes from NASA’s MODIS instrument (Moderate Resolution Imaging Spectroradiometer)
• data were collected from June through September 2001
• ocean data has two sources: (i) shallow water true color data, and (ii) global ocean color/chlorophyll data
• elevation data stem from the GTOPO 30 dataset by the U.S. Geological Survey’s EROS Data Center