Why is Callisto so bright?

Callisto: Facts About Jupiter's (Not So) Dead Moon. Voyager 1 image of Jupiter's moon Callisto from a distance of 350,000 km. The large 'bulls-eye' at the top is believed to be an impact basin formed early in Callisto's history. read more

Callisto is tidally locked, so the same side always faces Jupiter. Size: At 3,000 miles (4,800 km) in diameter, Callisto is roughly the same size as Mercury. It is the third largest moon in the solar system, after Ganymede and Titan. read more

Even though at a distance of 628,300,000 km Callisto is 180 times further away from us than our moon is from us, it is many times brighter than our moon when viewed through a telescope. read more

Callisto / k ə ˈ l ɪ s t oʊ / (Jupiter IV) is the second-largest moon of Jupiter, after Ganymede. It is the third-largest moon in the Solar System after Ganymede and Saturn's largest moon Titan, and the largest object in the Solar System not to be properly differentiated. Callisto was discovered in 1610 by Galileo Galilei. read more