Saturn is the second-largest planet in the solar system after Jupiter. By diameter, it is about nine times Earth's size, and its mass is 95 times greater. The chance has come to see this giant planet up close. The National Aeronautics and Space Administration (NASA) released a three-minute video on the 23rd (local time) as the "Astronomy Picture of the Day," showing the unmanned probe Cassini approaching Saturn.
Cassini was launched on Oct. 15, 1997, and entered Saturn's orbit in 2004. The first probe to make a close flyby of Saturn was the United States' Pioneer 11, which arrived in 1979, but Cassini was the first to orbit Saturn and conduct exploration.
The video is part of the 2018 IMAX space documentary In Saturn's Rings (2018), directed by U.S. filmmaker Stephen van Vuuren. Cassini approached Saturn in 2004 and took thousands of high-resolution photos, and after entering orbit it captured hundreds of thousands more.
NASA digitally corrected and edited some of the early images taken by Cassini at the time to create this video. The background music is "Adagio for Strings" by U.S. composer Samuel Barber, performed by the New York Philharmonic.
At first, the video shows Titan, shrouded in clouds, quickly passing at the lower left of Saturn. Titan has a diameter of about 5,150 km and is the largest of Saturn's 274 moons.
Saturn then appears larger and larger, and a small white dot approaches above it. That is Mimas, one of Saturn's moons. Recently, a wobble was observed, raising the possibility of liquid water inside.
Cassini flies over Mimas and shows the giant Herschel crater in sharp detail. The Herschel crater is named after Sir William Herschel, the British astronomer who discovered Mimas in 1789. Its diameter reaches 130 km.
Mimas is also famous for resembling the Death Star, the Galactic Empire's fortress with planet-destroying power in the movie Star Wars. In the film, the Death Star appears as a massive spherical fortress about 160 km in diameter, while Mimas is more than twice as large at 396 km.
After Cassini passes Mimas, Saturn's majestic rings fill the screen, and the shadows cast by the rings fall across Saturn's surface. In the final scene, the moon Enceladus approaches from a distance at the bottom of the frame.
Enceladus, along with Jupiter's moon Europa, is considered one of the most likely bodies to harbor an ocean capable of supporting life beneath a thick icy crust. In 2005, Cassini first observed plumes of water erupting through fractures in the crust at Enceladus' south pole, like geysers on Earth.
When Cassini ran out of fuel and could no longer carry out its mission, it deliberately dove into Saturn's atmosphere on Sept. 15, 2017, burning up from frictional heat and concluding its 20-year mission. The probe's official name is Cassini-Huygens. Cassini, the orbiter around Saturn, was developed by NASA, and Huygens, the lander that descended to Titan, Saturn's largest moon, was developed by the European Space Agency (ESA). Huygens landed on Titan, Saturn's largest moon, on Jan. 4, 2005.