Pronounced: "yoo ROH puh"

Orbit: Sixth of Jupiter's known satellites (670 900 km away), second of the Galilean moons.

Size: fourth largest of Jovian satellites; slightly smaller than Earth's moon.

Diameter: 3138 km

Mass: 4.80e22 kg (not quite sure what this means; a bit above Grade 9 Science/math)

Discovered By: Galileo and Marius

…When: 1610 AD

Primarily Composed of: Silicate rock

Crater count: very few

Size of Craters that ARE there: only three larger than 5k in diameter (have been found).

Atmosphere: Yes! Barely.

…Consists mostly of: Oxygen

Seen by spacecraft: Voyagers (not very well) and Galileo