OTD In Space - December 23: Giovanni Cassini Discovers Saturn's Moon Rhea
- last year
On Dec. 23, 1672, Italian astronomer Giovanni Cassini discovered Rhea, Saturn’s second-largest moon. [‘On This Day in Space’ Video Series on Space.com](https://www.space.com/39251-on-this-day-in-space.html)
Rhea is made up of rock and ice and is covered in craters. Rhea is also the only moon discovered to have an oxygen atmosphere. Rhea was the second moon that Cassini discovered. He discovered Saturn's moon Iapetus about a year earlier. Rhea wasn’t formally named until 1847. The British astronomer John Herschel suggested that Saturn’s moons should be named after the Titans. In Greek mythology, the Titans were the brothers and sisters of Cronus, who the Romans referred to as "Saturn." Cassini originally named the moons he discovered after the Sidera Lodoicea, meaning the "Stars of Louis," after King Louis XIV. Because Cassini discovered four of Saturn’s moons, NASA named a spacecraft after him.
Rhea is made up of rock and ice and is covered in craters. Rhea is also the only moon discovered to have an oxygen atmosphere. Rhea was the second moon that Cassini discovered. He discovered Saturn's moon Iapetus about a year earlier. Rhea wasn’t formally named until 1847. The British astronomer John Herschel suggested that Saturn’s moons should be named after the Titans. In Greek mythology, the Titans were the brothers and sisters of Cronus, who the Romans referred to as "Saturn." Cassini originally named the moons he discovered after the Sidera Lodoicea, meaning the "Stars of Louis," after King Louis XIV. Because Cassini discovered four of Saturn’s moons, NASA named a spacecraft after him.