NASA/JPL/Space Science Institute

Saturn's moon Mimas as imaged by NASA's Cassini mission.NASA/JPL/Space Science Institute

NASA’s Saturn-orbiting Cassini spacecraft this month made its closest pass yet of the odd, eyeball-shaped moon Mimas, which bears the scar of a massive, violent impact from its past.

The 88-mile wide Herschel crater is about one-third the diameter of Mimas, an inner moon of Saturn measuring about 246 miles in diameter. Herschel’s walls extend about three miles above the moon’s surface and parts of its floor are six miles deep.

Scientists aren’t sure why the giant impact that caused the crater didn’t cause the moon to break apart. Scientists may have more answers soon. On Saturday, Cassini passed within 5,900 miles of Mimas, taking pictures, temperature readings and measurements to learn more about what’s on its surface. The first images were released by NASA on Monday.