This is Blue Marble. It was the most accurate, highest resolution image of Earth ever—until they created the next-gen Blue Marble. It's the most famous, since it's the iPhone's default image. Now its creator has revealed all its secrets.
Unlike Apollo 17's photograph of the whole Earth, NASA's Blue Marble is not a real photograph. It's a composite made of many other images. A synthetic, but accurate and deliciously crispy representation of our home planet made by Robert Simmon:
One of the best surprises of my life was turning on my brand-new iPhone-before it had even been activated-glancing down at the screen, and seeing an image I had made. Apple chose the NASA Blue Marble for the default welcome screen and wallpaper, and I had no idea beforehand.
Simmon created the image using a 43,200-pixel by 21,600-pixel map of the Earth stitched together by Reto Stöckli. Stöckli used about ten thousand 300-megabyte satellite scenes captured by the Terra satellite over a period of 100 days. (Back then, Terra was NASA's latest Earth-monitoring satellite.) Stöckli took out all the clouds and left that huge image clean. Then Simmon came in and added some details: "To make the Earth look realistic, or at least how I imagined the Earth would look, I needed to do some work."
He used NASA's data on chlorophyll levels in the ocean—which is "a way of monitoring phytoplankton"—and textured Earth's water according to it. At the same time, he added the ice to the base texture, resulting in the image above.
Then he created a "map of clouds stitched together from 200 satellite scenes" as well as a topographic map to add elevation to our planet's land masses. Some of the clouds are cloned because, as he told me via email, "there are gaps between orbits near the equator, and there's no way to fill them with real data."
He entered all these textures into Electric Image, a classic Mac-based 3D software that was popular at the time, and the magic started to take form. (Ultra-nerd bonus: Electric Image was used by Industrial Light & Magic's John Knoll to create the space battle scenes in the original Star Wars trilogy remake too.)
There he mapped them onto a sphere, rendering separate images for everything: "land and ocean, specular highlight, clouds, a couple day/night masks, and atmospheric haze".
He finally brought these images into Photoshop and combined them for hours, "tweaking and re-tweaking transparency, layer masks, hue, saturation, gaussian blur, and curves to get an image that looked like the picture I had in my head." The result is beautiful. A sweet, beautiful lie. [Earth Observatory]
