Nasa's Cassini spacecraft will boldly go where no probe has gone before on Wednesday as it begins its descent to the region between Saturn and its innermost ring.
The spacecraft's “Grand Finale” will see it dip in and out of the planet's rings 22 times over the coming months before it enters the planet's atmosphere, burning up in the process.
Cassini, which launched two decades ago, has been circling the planet for 13 years but it has finally begun to run low on the propellant used to adjust its course, and scientists fear it damaging one of the moons it was sent to space to study for signs of life.
Nasa will hold a press conference on Wednesday at 11am BST as Cassini begins its first descent. Google has built a commemorative Doodle featuring the probe to mark the occasion.
What is Cassini?
Cassini-Huygens was a joint project between Nasa, the European Space Agency and the Italian Space Agency when the probe first launched in 1997. After seven years it arrived at Saturn on July 1, 2004 and it has been orbiting it ever since.
The Huygens probe attached to the spacecraft and travelled with Cassini until 2005, when it detached and landed on Titan in 2005. Both have beamed back invaluable images about Saturn and its moons.
What has it discovered?
The probe has been crucial to findings that Saturn's moons are among the most hospitable places in the Solar System for potentially supporting life. Only two weeks ago Nasa announced that Cassini had detected chemical reactions happening below the icy surface of Enceladus, suggesting life is possible there.
The mission also found that the moon Titan contains many earth-like features such as wind, rain and seas. Cassini recently flew closely by Titan in order to slingshot the spacecraft on its way into Saturn's inner orbit.
What will happen now?
Cassini may be beginning its journey to destruction, but the process will take several months. It will dip in and out of Saturn's rings 22 times over the next 142 days before its mission finally ends on September 15, reaching a top speed of 76,806 miles per hour.
The mission has been extended by Nasa three times, but with Cassini finally running out of fuel, scientists fear that it could crash into one of the planets that may support life. While unlikely, Nasa wants to avoid any microbes from earth that might remain on the probe contaminating the surface.
What does it hope to achieve now?
Although Cassini's time is nigh, its mission is hardly over: the probe will continue to relay back valuable information and images as it swoops between Saturn's rings.
Happening NOW: our final close flyby of #Saturn's moon #Titan, simulated here in @NASA_Eyes. Details: https://t.co/0QmYqS0KZR pic.twitter.com/PSf582lsjy
— CassiniSaturn (@CassiniSaturn) April 22, 2017
The mission will study the huge planet's gravity, as well as helping to establish how it and its rings were originally formed, examining its material in a way that has never before been done. Even as the spacecraft breaks up as it enters Saturn's orbit, it will be sending data back to earth in real time.
What can I see on Wednesday?
Nasa is holding a press conference at 11am BST – an hour after Cassini begins its dive, where it is expected to unveil the first live information about the mission.
The Telegraph website will be hosting the footage and providing live coverage of the event.