Day: March 6, 2021

In our photo-saturated world, it’s natural to think of the images on NASA’s Earth Observatory website as snapshots from space. But most aren’t. Though they may look similar, photographs and satellite images are fundamentally different. A photograph is made when light is focused and captured on a light-sensitive surface such as film or a charge-coupled device in a digital camera. A satellite image is created by combining measurements of the intensity of certain wavelengths of light that are visible and invisible to human eyes.

Why does the difference matter? When we see a photo where the colors are brightened or altered, we think of it as artful (at best) or manipulated (at worst). We also have that bias when we look at satellite images that don’t represent the Earth’s surface as we see it. “That forest is red,” we think, “so the image can’t possibly be real.”

In reality, a red forest is just as real as a dark green one. Because satellites collect information beyond what human eyes can see, images made from other wavelengths of light look unnatural to us. We call these false-color images. To understand what they mean, it’s necessary to understand exactly what a satellite image is.