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So Long Cassini
1997 may feel a billion miles distant, the internet, digital technology that promises smart this that and the other didn't exist on October 15th, where the world had not long recovered from the seismic shock of Princess Diana's death, and the World Trade Center remained a fixture on the New York skyline. Two decades though are less than a blink of an eye regarding the dance of the planets around the Sun, but the space of this time (pun intended) has changed the way that we realise the laws of physics can manipulate our Solar System. Saturn has captured people's imaginations almost as much as Mars; the complex ring system always remained a cause for speculation as for the planet and its numerous moons resembles a kind of mini Solar System that is easier to investigate than the vaster one we occupy. The gravity that keeps the rings apart and causes them to smash together, as well as moons acting out tidal forces on them and Saturn, in particular, exerting pressure on its satellites, were all aspects that we couldn't have guessed at 20 years ago.
Launched from Cape Canaveral, Florida in 1997, Cassini had an extended journey around Venus, Earth and Asteroid 2685 Masursky. Cassini travelled for more than seven years and a billion miles; the probe reached the ringed planet in the summer of 2004, and the mysteries began to unfold thick and fast. A second probe existed attached to Cassini, manufactured by the European Space Agency, known as Huygens that had a particular destination, where Cassini aimed for the entire Saturn system, where Huygens set its sight on the planet's largest moon - the second biggest in the Solar System overall - Titan. Observations of the moon hinted at dense cloud cover and cosmologists believed it could provide clues to how life on Earth began deep in our world's past. On Christmas Day, 2004, Huygens detached from Cassini and started its journey into the thick clouds of Titan. The view Huygens offered when it penetrated the atmosphere stunned astronomers as a live feedback revealed the world as far more exciting than anyone could guess. Unveiling a moon riven with rugged, mountainous landscapes and what's more, liquid flowing on the surface!
However, the liquid on Titan's surface consists of methane and not water, the temperatures of -180ºc allow what we know as a gas on Earth to flow in a fluid state. Methane rain also falls from the Titan sky as slow as a gentle snowstorm on Earth, pooling into rivers and lakes, a stunning revelation that held many implications for astronomers on Earth who felt Titan allowed them to glimpse back through the clouds of 3-4 billion years. The marvels of Cassini did not end there though; the probe took images of the moon, Jupiter and its faint rings, as well as Asteroid 2685 Masursky, additionally confirming Einstein's theory of General Relativity. Beaming radio waves that travel past the sun, it used the mass of our star to spot warps in radio waves and further bolster Einstein's discoveries. Cassini also spent 13 years studying Saturn and found three new moons orbiting the planet, watching the formation of rings while shepherded by smaller moons.
Saturn's atmosphere also got a closer peek thanks to Cassini, witnessing the Great Storm in 2010, a hexagonal jet stream that flowed over the vast world's poles and aurorae similar to what we see on Earth. The probe also glimpsed the wider Solar System beyond Saturn, recording the transit of Venus with the Sun for the last time in two centuries and a couple of snapshots of a distant azure Earth. Saturn's family of moons displayed a vast array of oddities, such as Hyperion that resembled a rocky sponge, Phoebe has water ice and Iapetus demonstrated a massive ridge running around the entire satellite but that data nearly lost due to Cassini getting hit by a cosmic ray. Though Cassini's magnum opus was the moon Enceladus, which in 1997 the best minds thought of as merely an icy globe smaller than our moon. However, one flyby witnessed plumes erupting from Enceladus's south pole, a second flyby directed Cassini into one of the plumes, learning they originated as jets of water, containing organic material akin to hydrothermal vents at the bottom of Earth's oceans. We now understand that Enceladus endures such tidal forces from Saturn's immense gravity that the moon stretches, putting friction on an otherwise frozen core, making it molten, thus cooling ice into a vast ocean beneath a crust of ice.
As of September 15th, 2017, Cassini's 20-year journey came to an end, allowing scientists to learn more about the way physics can manipulate its surroundings, providing insight into how potentially rich with life our Solar System could be, especially in a place so barren it makes Antartica look tropical! Though now it took a nose dive into Saturn's enormous atmosphere where it will burn up, to preserve any potential life that may exist on any of the moons, ending its 13 years of service to scientific endeavour and service to science. Anyone watching the sky and curious of our life in the universe will bid the probe a fond farewell!