A thrilling epoch in the exploration of our solar system came to a close today, as NASA’s Cassini spacecraft made a fateful plunge into the atmosphere of Saturn, ending its 13-year tour of the ringed planet.

Cassini carried a passenger to the Saturn system, the European Huygens probe—the first human-made object to land on a world in the distant outer solar system. After 20 years in space — 13 of those years exploring Saturn — Cassini exhausted its fuel supply.

To its very end, Cassini was a mission of thrilling exploration. Launched on Oct. 15, 1997, the mission entered orbit around Saturn on June 30, 2004 (PDT), carrying the European Huygens probe. After its four-year prime mission, Cassini's tour was extended twice.

Artist's concept of Cassini 's controlled atmospheric entry into Saturn. The Cassini space probe was deliberately disposed of via a controlled fall into Saturn's atmosphere on September 15, 2017, ending its nearly two-decade-long mission.

The Cassini spacecraft, in orbit around Saturn since mid-2004, will plunge into Saturn’s atmosphere in the early morning hours of Sept. 15. A flyby of Saturn’s largest moon, Titan, on Sept. 11...