NASA's Cassini spacecraft will make its final plunge into Saturn's atmosphere in just 30 days, ending a 13-year mission around our solar system's second largest planet.

Since arriving at the planet on July 1, 2004, the first spacecraft to orbit Saturn has made several landmark discoveries and beamed a vast array of stunning images back to Earth.

Here, looks back at the mission's most important revelations before the probe burns up in Saturn's atmosphere on September 15, bringing an end to its incredible 2.2 billion-mile journey.

1. Enceladus could harbor alien life

New research suggest warm oceans beneath Enceladus' icy crust.
Cassini detected hydrogen from hydrothermal vents in ice plumes from Saturn's ocean-bearing moon Enceladus. The discovery makes Enceladus the only place beyond Earth where scientists have found direct evidence of a possible energy source for life.

"Enceladus has almost all of the ingredients you would need to support life as we know it on Earth," NASA said.

2. Titan is an Earth-like world
Titan moon
Little was known about Saturn's largest moon until Cassini sent the Huygens probe to land there - making it the first landing in the outer solar system and the farthest moon where any probe has landed.

The spacecraft found an Earth-like world with lakes and seas composed of liquid methane and ethane near its poles and, deep below its surface, a large internal ocean.

"Titan is the only other place in the solar system known to have an Earth-like cycle of liquids flowing across its surface as the planet cycles through its seasons," NASA said.

3. Saturn's rings are not uniformly flat
Saturn's rings
Images captured by Cassini in 2009 revealed that, contrary to previous belief, Saturn's rings are not uniformly flat, showing ridges similar in height to the Rocky Mountains within the rings.

NASA said of the discovery: "It's like putting on 3-D glasses and seeing the third dimension for the first time. This is among the most important events Cassini has shown us."

4. The region between Saturn and its rings is 'the big empty'

Cassini began its Grand Finale in April, starting a series of 22 weekly dives between Saturn and its rings. The dives have so far revealed that the gap itself is free of almost anything at all - even spacedust.

"The region between the rings and Saturn is 'the big empty,' apparently," NASA said.

5. Saturn has seven hidden moons

Seven previously unknown moons were discovered by the spacecraft during its orbit of Saturn. These include Methone, Pallene, Polydeuces, Daphnis, Anthe and Aegaeon. The seventh moon, discovered in 2009, is named S/2009 S 1.

In January 2017 Cassini obtained the closest view yet of Daphnis - the 'wavemaker moon.'

Saturn moon