914-mile-wide Iapetus, one of Saturn’s 61 moons, is crescent-lit in this raw image from the Cassini spacecraft.

Iapetus orbits Saturn at over 2 million miles away, 8 times farther than our moon is from us. Its surface is marked by a side covered in bright, reflective material and a side covered by dark material. The exact process that causes this is still undetermined.

Image: NASA/JPL/Space Science Institute