The Cassini space probe’s 20-year journey has come to an end.
Prof. John Zarnecki, President of the Royal Astronomical Society, said:
“I worked on Cassini/Huygens for more than 20 years so of course I feel slightly sad. But it’s given me the most wonderful ride and it delivered my instrument to the surface of Titan where it’s still sitting! It has shown Titan to be even more wonderful than we had ever imagined – we’ve seen seas and lakes and rivers and dune fields and clouds and rain and more.
“The data we collected is unlikely to be bettered for many decades to come. The mission has not only been a wonderful scientific success but has also shown what can be achieved when scientists and engineers from across the world can work together with a common purpose to realise lofty goals.”
Prof. Jeffrey Kargel, Senior Associate Research Scientist at the University of Arizona, said:
“The Cassini mission is soon to end in a programmed, fiery plunge into Saturn. The mission design has a brief transition from a Saturn orbital mission to a Saturn atmospheric probe mission. Data about Saturn’s atmospheric composition will be gathered and relayed to Earth as it starts atmospheric entry above the cloud tops until its thrusters become unable to deal with the aerodynamic forces and it first spins out of control, losing contact with Earth, then almost immediately breaks up– the first human-made meteor in Saturn’s sky.
“I am not on the Cassini Team, but I have been among the scientists thrilled by the data and have worked on modeling the composition of the tenuous organic clouds and hazes in Titan’s atmosphere and the composition of that moon’s surface lakes and seas. The greatest thrill of the mission for me was the discovery of giant geyser-like plumes blasting from the south polar region of the tiny icy satellite Enceladus, and then a recognition that this object has a thin icy shell overlying a still-liquid ocean of saline water. What an amazing pair of discoveries! It should not have been a total surprise to me, because the first two scientific presentations I ever made, back in 1983 and 1984, were based on Voyager 2 images of Enceladus, where I used surface features to infer the occurrence of explosive cryovolcanic jetting from a chains of pits, and the shifting and compressive crumpling of an icy shell over a possible liquid water ocean. But nothing– not even with my prior expectations of something amazing at Enceladus– could prepare me for what was actually seen. Geysers jetting off into the blackness of space around Saturn– that’s pretty amazing. The sodium carbonate and bicarbonate composition of the geysers and by extension of the ocean came as a big surprise and has me looking here on Earth for evaporative saline lakes that have similar compositions– and lots of well-adapted microbial life. So, yes, Encleadus could have life despite its caustic hypersaline ocean composition.
“A tremendous pleasure– something very directly connected to the human spirit and appreciation of beauty– has been the endless stream of stunning vistas of moons and rings and Saturn’s cloud tops. The Cassini teams from the engineers to the scientists deserve a global round of applause for what they have accomplished for all of us.”
Prof. Mathew Owens, Professor of Space Physics at the University of Reading:
“Cassini made many, many discoveries; about Jupiter and Saturn’s atmospheres, magnetic fields and aurora and Saturn’s highly structured rings. But some of the most exciting discoveries are about Saturn’s moons and what they tell us about the possibility of life on other planets. On a flyby of the moon Enceladus, it was found to have giant plumes of material streaming away from its surface which contained ice, suggesting the moon may have a subsurface ocean. And the Huygens probe was the first to land on the moon of another planet. On Titan’s surface, it found evidence of “rain” erosion and dry lake beds, though likely from liquid methane, rather than water. Titan’s atmosphere was found to contain complex molecules that may be the building blocks of life.”
Prof. Martin Rees, Astronomer Royal, said:
“We’ve now reached the grand finale of what’s surely one of the greatest scientific and engineering achievements in space exploration. Cassini has given us a cornucopia of information about Saturn, its rings and its moons.
“Moreover, it carried in its cargo bay a smaller robotic probe, Huygens, built by the European Space Agency, which achieved a ‘soft landing’ on Saturn’s giant moon Titan, revealing lakes and rivers of liquid methane on that exotic world. Close flybys of a smaller moon, Enceladus, confirmed that there was an ocean under the ice – perhaps the most likely location in our solar system for life.
“It’s more than 20 years since Cassini started its journey. It was built using 1990-s era technology. When we realize how spectacularly robotics and smartphones have advanced since then, we realize how amazing Cassini’s achievements have been – and how much more we well learn from state-of-the-art follow-up missions.”
Dr Phil Sutton, Astrophysicist at the University of Lincoln, said:
“Friday 15th September signals the end of the Cassini spacecraft after more than 13 years successfully in orbit around Saturn. Many of the latest images Cassini has sent back to Earth are showing features in Saturn’s rings, its atmosphere and its many moons that we aren’t currently able to explain. The Cassini mission may have ended, but it has left behind a legacy of data surrounding one of the most exciting and dynamic systems in our solar system, which it will take another decade for scientists to try and understand.”
Prof. Emma Bunce, Department of Physics and Astronomy at the University of Leicester, said:
“My involvement in the Cassini mission began not long after the end of my PhD work in around 2002. My PhD supervisor Stan Cowley was a Co Investigator on the Imperial College led magnetometer (he still is, and I am too now), and he decided it was time to switch our attention from Jupiter to Saturn around that time. We started to work on the magnetometer data from interplanetary space as Cassini made its long journey to Saturn. From there, I was welcomed into the team and have worked on many aspects of the structure of Saturn’s magnetosphere and nature of the aurora in the upper atmosphere since that time. The unprecedented data from the Cassini mission has enabled the magnetometer team to make many amazing discoveries about the Saturn environment, and we still have much to learn from the Grand Finale orbits which we will be analysing for months to come.
“I owe a great deal to this mission, and I am so grateful for the opportunity to have been involved – in the lifetime of Cassini my career has progressed from new post-doctoral researcher to Professor and a significant fraction of that progression is owed to the fact that I was given the opportunity to be part of this fantastic team.”
Dr Jane Hurley, Project Manager at Science and Technology Facilities Council RAL Space, said:
“Cassini has provided the international science community with decades of irreplaceable insight into Saturn and its moons, and inspiration to generations of scientists and engineers. As part of both the CIRS instrument science team and operations team, I have been very lucky to be part of such a successful mission – not least because of the collaborations and working relationships that become lifelong friendships. I shall be raising a pint or two with the Oxford team at lunch tomorrow; and a toast to the Cassini/CIRS operations team in the UK, Europe, at NASA/Goddard and NASA/JPL for the years of hard work behind the scenes that have given us the mission we’re celebrating today.”
Dr Caitriona Jackman, Associate Professor in Physics and Astronomy at the University of Southampton, said:
“I’ve had the immense privilege of working with Cassini data from the very beginning of my PhD which started back in 2003 when the probe was just on its way to Saturn. My supervisor was part of the magnetometer team – the instruments on the spacecraft that measure the magnetic field, – so I was analysing that data throughout my PhD.
“Saturn is a really beautiful planet; the rings are iconic and everybody can picture what it looks like in the night sky. And, as the seasons change and the tilt of the rings change, you get a different view of Saturn every time which is very special.
“Over the years, my research has been to study the magnetic field of Saturn, to study the aurora (the northern and southern lights), so having spent most of my waking hours for the last 13 years thinking about Saturn, it’s going to be quite strange for Cassini to no longer be actively taking data.
“We went there with certain questions. We wanted to chart the magnetic field of the planet, we wanted to examine the moons, we wanted to land on Titan – which we did successfully – but we’ve also had many surprises.
“For example, in charting the moons of Saturn we discovered many more moons and we also discovered that one of the moons – Enceladus – is producing geysers of water vapour from cracks on the surface. Such unexpected discoveries can change the course of a mission.
“I think it is important to emphasise that the mission doesn’t end on the 15 September in the sense that the data will be there and will be actively analysed for many, many years to come.”
Prof. Stanley Cowley, Professor of Solar Planetary Physics, University of Leicester Department of Physics and Astronomy:
“The Cassini mission to Saturn has represented a massive chunk of my scientific career, having originally been involved in the successful bid to NASA to build its magnetic field instrument when working as Professor of Physics at Imperial College in 1990. Since moving to Leicester in 1996 Cassini-related work has been a central part of my research programme, consisting of both data analysis and related theoretical studies, leading to the publication of over a hundred research articles in international journals and the training of a dozen doctoral research students.
“Our work has focused on the magnetic effects of the electric currents that flow in Saturn’s outer environment, figuring out the physical origins of the mega-amp currents that flow around Saturn in the equatorial plane, making the first observations of the polar currents that light up Saturn’s polar auroras, and characterizing the weird oscillations in the gas and field near the ~11 hour planetary rotation period that pervade Saturn’s outer regions.
“It will be sad to see Cassini go on Friday, especially as the instrument we built is still working perfectly after 20 years in space, but we recognise that it is important to bring the mission to an end in a tidy and controlled manner.”
Dr Leigh Fletcher, Senior Research Fellow in Planetary Science, University of Leicester Department of Physics and Astronomy:
“The most important credential that this mission can be proud of is its international nature. 27 nations, including the UK, were involved in this fantastic mission. Cassini-Huygens will truly be the benchmark against which all future missions are compared.
“This has been a bittersweet week, watching as my Cassini colleagues gather for the final time to watch the end of this 20-year journey. This heroic spacecraft has done everything we’ve ever asked of it, even fighting with its last moments to deliver new scientific insights back to Earth. So although I’m sad that Cassini’s exploration will now be a part of the history books, I think we can be proud of everything that this mission has accomplished.
“It just shows what wonders can be achieved when 27 nations work together.”
Prof. Andrew Coates, Professor of Physics, Head of Planetary Science Group, Mullard Space Science Laboratory, said:
“The Cassini-Huygens mission has been one of humankind’s great voyages of discovery, and it’s been a privilege to be part of this stunning adventure for the last 28 years. The mission has changed the way we think of where life may have developed beyond our Earth. As well as Mars, outer planet moons like Enceladus, Europa and even Titan are now top contenders for life elsewhere. We’ve completely rewritten the textbooks about Saturn, the rings, Titan and Enceladus, and the other icy satellites, and Huygens landed on Titan for the first time. With our own instrument, the Electron Spectrometer, part of CAPS on the Cassini orbiter, we discovered complex prebiotic chemistry in Titan’s atmosphere, water clusters and ice grains from Enceladus’ subsurface ocean, found atmospheres of Saturn’s rings and of Rhea and Dione, measured surface charging at Hyperion, and detected the electrons causing Saturn’s aurora. Cassini data have already provided great opportunities for generations of PhD students and postdocs, with much more to come.”
Dr Dave Clements, Astrophysicist at Imperial College London, said:
“Cassini has turned the moons of Saturn from dots of light into places, from Huygens landing on Titan, with its ice rocks and seas of methane, to the plumes of water being ejected from Enceladus, to bizarrely shaped moons like Hyperion and Pan. It has shown us that the Solar System is an even more bizarrely wonderful place than we had previously thought.”
Dr Marina Galand, Reader in Planetary Sciences at Imperial College London, said:
“Despite all the amazingly rich and unexpected dataset that the Cassini spacecraft has been sending us back from the Saturnian system since its arrival in 2004, we are deeply excited by the dataset which Cassini has been returning over the past weeks due to its uniqueness (e.g., first ever in situ gas and plasma measurements in the upper atmosphere of a giant planet). This dataset is filled with unanticipated findings. Cassini has not finished to surprise us all the way to the very end.
“Tomorrow is going to be greatly exciting to get data so close to the planet as well as extremely sad with the destruction of the spacecraft… but the Cassini scientific adventure is going to continue over the coming decade(s) with further analysis and interpretation of the fantastic dataset returned by Cassini over the past 13 years!”
Prof. Mathew Owens, Professor of Space Physics at the University of Reading:
“In its 20-year mission, Cassini’s numbers alone are astonishing. It’s discovered six Moons, taken half a million images and returned nearly a terabyte of data that has underpinned more than 4,000 scientific papers. No doubt scientists will be analysing the information from its final, one-way trip into Saturn’s atmosphere for years to come. This has been a hugely successful mission and a testament to all involved.”
Dr Marek Kukula, Public Astronomer at the Royal Observatory Greenwich, said:
“The Cassini mission has been a tremendous adventure. It’s completely changed our understanding of Saturn while sending back a stream of astonishingly beautiful images of the planet’s clouds, rings and moons, allowing us to feel almost like we’re out there with the spacecraft. I’ll definitely shed a tear when Cassini sends its last data back to Earth but I’ve no doubt that the achievements of the mission are going to be celebrated for decades to come”.
Prof. Michele Dougherty, Professor of Space Physics at Imperial College London, said:
“I have a mixture of emotions; sadness that it is coming to an end, we have worked together so well and have produced such spectacular results and I feel so privileged to have been a part if it; real pride at what we have achieved over the years but also some feeling of relief now, the last 6 months have been very intense and I am pretty exhausted!”