When you’re looking at images of cratered worlds taken from spacecraft, do you see domes, bumps or mounds instead of craters? That’s because our brains are used to perceiving images as lit from above. This optical illusion is called the crater-dome illusion, or relief inversion. One quick way to try to get the images to “pop” into their correct relief is to rotate the two-dimensional images until the light source is from above.
In the example above, do you see the two images of Victoria Crater on Mars as a dome in one and a crater in the other? Or maybe two craters or two domes? Perhaps they even switch while you’re looking at them. The Mars Reconnaissance Orbiter captured these images of the 1/2 mile-wide crater in 2006. It’s an impact crater with sand dunes on the crater floor.
The same illusion happens when we look at satellite images from Earth as well. We often see images of Earth with north at the top. But when the image is of the Northern Hemisphere, the angle of sunlight is coming from below, and we can experience relief inversion. So it can happen with more than just craters. Below is an image of the vast canyonland area of Grand Staircase-Escalante National Monument in the United States. The first shows the view with north up, like you would see on a map. But the view is lit from below.
Does the second image, rotated so that north is down, look more like a canyon system to you?
Usually we know if something is a crater versus, say, a volcano. But bizarre landscapes can be misleading. The image below shows pink sand dunes and white salt flats. But at first blush, with north up, it looks as if it’s pinkish canyons.
Below is a relatively recent crater on the moon. Again, we see the image on the left looks more like a raised dome, possibly a volcanic feature. But in reality, the landform is a crater.
Here are two more examples. Remember, if you want to invert the view, try rotating it!
Try the next one yourself. Don’t feel bad if you can’t make it stop looking like a bump. Once your brain sees it as such, it will try to hold onto that view!
Bottom line: The crater-dome illusion happens when you look at an image of a crater and the angle of the light causes it to appear as a dome, bump or mound instead of a crater.
The post The crater-dome illusion: When your brain inverts the image first appeared on EarthSky.
