Today is the end of era and a project that has lasted around 30 years, given us a spectacular insight into one of the most beautiful objects in the solar system. Today is when the Cassini mission finally ends by plummeting into Saturn’s atmosphere and will be destroyed by re-entry and the intense pressure of it’s atmosphere.
When Cassini was first devised and started development started Ronald Regan was still president of the United States, Voyager 2’s final calling had not yet taken place and the internet was not widely used. The world was a very different place. Launched in 1997 and passing by Venus and Jupiter on the way to Saturn it saw in the new millennium on the way to it’s destination. Arriving after a seven year journey in 2004.
It’s mission was bold, to launch and land a small probe – Huygens onto the surface of Saturn’s’ largest moon Titan and run experiments to see what it’s surface and atmosphere are like while the Cassini orbiter relayed all the data back to Earth. After a short time the Huygens probe would stop operating, leaving the lone Cassini orbiter to carry on gathering data on Saturn and it’s system. Initially this was to only be for a few years, but two extensions have seen it last until 2017. Now, becasue of the orbiter’s dwindling fuel supply it will dive into Saturn’s atmosphere on September the 15th after a series of atmosphere skimming ring dives between the planet and it’s rings dubbed ‘The Grand Finale’. Cassini will be burned up in Saturn’s atmosphere becoming part of the planet, destroyed to stop it contaminating any of Saturn’s potentially life harbouring moons. This will ensure they are preserved untouched for future missions.
On the 15th October 1997 under the veil of night, Cassini was launched on the start of a seven year journey to Saturn on a course that would take it past Venus and Jupiter before arriving at Saturn in 2004.
On the 1st July 2004 Cassini entered orbit around Saturn and immediately began sending back pictures and data. One of Cassini’s first jobs was to map out the terrain of Saturn’s moon Titan so that a suitable landing site could be found.
On the 25th of December 2004 the Huygens probe was released from Cassini and began it’s approach and descent into Titan’s atmosphere. Titan is Saturn’s largest moon and is the only moon in the solar system with a thick methane atmosphere. This discovery was made by the Voyager 1 flyby mission and since then the possibility of liquid methane lakes and the possibility of some kind of life being able to exist on Titan has fascinated scientists.
Artists impression of Huygens on Titan
Huygens landed on Titan on the 14th of January 2005 on it’s way down it spent about 90 minutes descending through Titan’s atmosphere. Taking pictures that were relayed back home via the Cassini spacecraft.
Titan as taken by Huygens on the its descent
Huygens is the first and currently only spacecraft to land on a world in the outer Solar System. Once the small craft had landed it took the first pictures of the surface of this mysterious world.
The surface of Titan
The Huygens probe was expected to only have enough battery life for a few minutes on Titan. As it turned out Huygens lasted about 90 minutes, took pictures and analysed the surface. The stone seen in the picture are made of water ice and the red film is an outer layer of Methane. It was anticipated that Huygens could encounter and indeed land in a lake of Methane and was designed to be able to survive this. As it turned out it found no evidence of this. Since then, data returned from Cassini suggests these Methane lakes do exist particularly at the poles of the moon.
The Huygens probe is the first and currently remains the only man made object to land on a world in the outer solar system.
The Cassini orbiter lasted much longer than the little Huygens probe, much longer than it was originally meant to. The original mission was to observe the planet during it’s Equinox which occurred in 2009. The mission was extended to observe the planet at it’s summer solstice in 2017 which gave the orbiter another 155 orbits of Saturn and further observations of Titan and Enceladus. In that time Cassini has made observations on aurora at it’s poles, much like we have here on Earth.
At the poles, the clouds were found to form a hexagonal shape. This alone has kept scientists busy finding an explanation.
Haxagonal clouds at Saturn’s north pole
The magnificent rings of Saturn have been observed ever more closely in the last months as Cassini carries out it’s last flyby’s.
The majestic beauty of them hides a highly complex structure, shaped and formed by Saturn and it’s orbiting moons.
The size of the objects forming the rings sorted into a seemingly orderly fashion with larger like ice towers on the outer rings..
Close up of Saturn’s rings
Wave patterns on Saturn’s Rings
Gravity waves forming them into waves as you might find in water on Earth.
Close up of Saturn’s rings
Cassini has observed many of it’s moons in closer detail than ever before, giving us a greater insight into how this planet and it’s system was formed.
But the shining star of Saturn’s moons has been Enceladus. It’s surface showing signs of old and new activity and the greatest discovery being of it’s plume of water ice, shooting into space.
Keep an Eye on us
Despite the distance, Cassini has been keeping an eye on us too from time to time:
Earth and Saturn captured by Cassini
The tiny dot is all of us – once again put into perspective we are tiny, living on a spec in the cosmos. But Cassini has looked back at the planet from where it came for the last time…
As space probes go – Cassini has had a good running, but Cassini is at Journey’s end:
In order to preserve the purity of Saturn’s moons and not contaminate them with bacteria Cassini takes it’s plunge into Saturn’s atmosphere today. It will forever become a part of the planet which it helped it’s creators to study. Saturn and it’s majesty has forever captured human fascination and will continue to do so. As the tool which has brought us that much closer to the ringed planet Cassini has also captured our imaginations and a little of our hearts.
While it may not be preserved for all eternity like the Voyagers, Cassini’s legacy will last, long after it’s demise and what it has brought us will forever be remembered. As it takes it’s plunge it will send us back data and images of Saturn, closer and more intimate than we have ever had before. It will go where no human can or maybe ever will go.
Clouds of Saturn in false colour
That’s a crowning achievement and a fitting last act for perhaps one of the most successful and awe inspiring spacecraft ever built.
Farewell Cassini, we know you’ll do us proud one last time.
More information on the Cassini mission can be found on NASA’s Cassini page:
NASA’s Cassini Mission Page
Grand Finale Overview and Countdown
©Simon Farnell 2017
No Ownership claimed on any of the images or materials. Credit to NASA and JPL.