Cassini's 20-year mission exploring Saturn

NASA's Cassini spacecraft completes its 20-year mission exploring Saturn on Friday, when it will send final images before plunging into the planet's atmosphere.

CASSINI'S MISSION EXPLORING SATURN:

Since leaving Earth in October 1997, the spacecraft:

* Travelled for seven years to reach the gas planet

* Spent 13 years orbiting it, equal to 293 times

* Discovered six moons

* Took 450,000 images

* Collected 635GB of data

* Carried the Huygens probe, which landed on Saturn's largest moon, Titan

* The Titan landing was the most distant landing from Earth to date

* Discovered rain, rivers, lakes and seas of liquid methane on Titan

* Found active water/ice plumes on the moon Enceladus

* Showed structures 2.5km high in Saturn's rings

* The mission cost $US3.26 billion ($A4.06 billion)

Source: CSIRO