The death of Cassini

The spacecraft Cassini was launched nearly twenty years ago—on October 15, 1997—to study Saturn and its moons. After two decades of faithful service, it took its “suicide plunge” yesterday, incinerating itself in Saturn’s atmosphere. Both NASA and the New York Times (100 pix!) have images from the mission, and here are a few. NASA’s images depict the final photos sent by Cassini, while the NYT gives a panoply of pictures over the vehicle’s history. (The head of Cassini imagine was, of course, Carolyn Porco.)

The sites’ captions are indented:

(NASA): Impact Site—Cassini’s Final Image: This monochrome view is the last image taken by the imaging cameras on NASA’s Cassini spacecraft. It looks toward the planet’s night side, lit by reflected light from the rings, and shows the location at which the spacecraft would enter the planet’s atmosphere hours later.

(NASA): Enceladus setting behind Saturn:

This view of Enceladus was taken by NASA’s Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back.

(NASA) The “final ringscape”:

This image of Saturn’s rings was taken by NASA’s Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back to Earth.

Here’s NASA’s video, accompanied by mournful music, of the last pictures transmitted by Cassini. I have to say, this self-destructive plunge into Saturn is saddening, even though it’s a machine : it’s almost as if a friend we’d known for a long time suddenly died. But that machine carried with it the best of humanity—an insatiable curiosity and the brainpower to satisfy it.

The rest of the photos are from the NYT, with their captions:

Cassini arrives at Saturn. Cassini arrived at Saturn in 2004, after a seven-year voyage. It was the first spacecraft to orbit the ringed planet.

Northern winter. Like Earth, Saturn has a tilted axis. Cassini arrived in the depths of northern winter, with Saturn’s rings tipped up and its north pole in darkness.

A yearlong storm. The change in seasons brought a huge storm that wrapped around Saturn’s northern hemisphere. Cassini detected lightning deep within the planet.

Saturn’s rings. Cassini used Titan’s gravity to tour Saturn’s rings, climbing high above the ring plane and threading gaps between the rings.

 A detailed view of the B ring.

For 13 years, Cassini joined the intricate dance of Saturn’s 62 moons.

The moons Rhea and Epimetheus.

But of all of Saturn’s moons, Enceladus was the most surprising.

The icy crust of Enceladus encases an ocean of water, dotted with hydrothermal vents and warmed by the stretching and squeezing of Saturn’s gravity.

Cassini flew through the plumes many times. The spacecraft’s instruments detected several molecules associated with life, but were not designed to search for microbes.

Geysers erupting during a Cassini flyby.

Spray from Enceladus forms Saturn’s diffuse E ring.

The Times has a gazillion more pictures, including many of Saturn’s moons. Go have a look.



  1. Laurance
    Posted September 16, 2017 at 8:39 am | Permalink

    Who needs woo-woo when Real Science is so glorious and beautiful?

    • Ben Ricker
      Posted September 16, 2017 at 12:44 pm | Permalink

      Exactly my thoughts. Who needs a God when we have this. We are the Gods…flawed Gods though we be.

  2. ThyroidPlanet
    Posted September 16, 2017 at 8:41 am | Permalink

    Thanks for writing something about this.

    The only image I really needed – in addition to the absolute final in Cassini’s life – was the setting Enceladus, gave me a little flutter in my chest.

    • gravelinspector-Aidan
      Posted September 16, 2017 at 12:11 pm | Permalink

      Emily Lakdawalla, a journalist for the Planetary Society, put together some of the last images into an animation.
      Better check you’ve got your nitroglycerine to hand.
      Blog. And hopefully the image.

  3. David Harper
    Posted September 16, 2017 at 9:26 am | Permalink

    Whilst Cassini was managed by NASA through the Jet Propulsion Laboratory, it was an international project. Major spacecraft components were built in Europe, and the Huygens lander was built by the European Space Agency. The science teams included astronomers and engineers from many countries. This is something else which should be recognised and celebrated. The world came together to explore Saturn.

    • nwalsh
      Posted September 16, 2017 at 11:55 am | Permalink

      Indeed, well said

    • Diane G.
      Posted September 17, 2017 at 4:10 am | Permalink

      Thank you.

    • Posted September 19, 2017 at 11:46 am | Permalink

      Gene Roddenberry used to say that the expense of space flight was a good thing, because it forces people to work together.

  4. Posted September 16, 2017 at 9:38 am | Permalink

    Anybody else experience an optical illusion from the storm photo?

    • gravelinspector-Aidan
      Posted September 16, 2017 at 12:14 pm | Permalink

      Which illusion? That the storm clouds are floating above the main part of the cloud decks?
      I don’t think it’s an illusion. As systems for pumping heat out of the atmosphere faster, storm clouds typically do rise above the level of regular clouds.

      • Ben Ricker
        Posted September 16, 2017 at 12:47 pm | Permalink

        Also, Saturn is a gas giant so its all cloud deck. Its all “regular clouds”.

        • gravelinspector-Aidan
          Posted September 17, 2017 at 6:38 am | Permalink

          Welllll, until you get above the critical point of 25:75 He:H mixture (with dirt), at which point it becomes somewhat academic.
          One of the as-yet unanswered questions about both Jupiter and Saturn is whether they contain an inner core of metallic hydrogen demiscing from liquid (supercritical) helium. Both should, according to our experimental work (Carnegie, Washington published on the question a few months ago) but the helium and dirt makes it less than certain. The magnetic fields argue for a liquid conductor, but it’s still not clear. The moment of inertia might help us to tell (but we don’t know how much dirt there is in either planet, and in particular the size of the core in Jupiter before it started to accrete gas big-style).All of which were questions that the close late-mission orbits of Cassini and Juno were planned to illuminate. And which will be the subject of intense study this weekend and in coming weeks.

          • Diane G.
            Posted September 17, 2017 at 4:54 pm | Permalink

            Very interesting, thanks, Aidan.

            • gravelinspector-Aidan
              Posted September 18, 2017 at 8:55 pm | Permalink

              @PlutoKiller (Mike Brown, CalTech) was going on about it to moderate length in a course on building solar systems on Coursera a few months ago. The course has (or is about to) respawn.

              • Diane G.
                Posted September 19, 2017 at 3:40 am | Permalink

                Thanks again, but I think your level of explanation is probably all my brain can wrap around these days… 😉

      • Posted September 16, 2017 at 8:12 pm | Permalink

        I see the clouds moving.

        • gravelinspector-Aidan
          Posted September 17, 2017 at 6:40 am | Permalink

          It’s certainly a very dynamic photo. Reminds me – unsurprisingly – of turbulence behind a boat. But I don’t have an illusion of motion.

  5. Posted September 16, 2017 at 10:00 am | Permalink

    The collection of Cassini pictures in the NYT is spectacular.

  6. Richard Bond
    Posted September 16, 2017 at 10:58 am | Permalink

    One of the minor (!) achievements of James Clerk Maxwell was to calculate (published in 1859, a good year: he also presented the Newtonian anomaly of the specific heat of gases, which could only later be explained by quantum mechanics) that Saturn’s rings could only be stable if they were composed of small solid particles. That was confirmed 120 years later by one of the Voyager spacecraft.

    • gravelinspector-Aidan
      Posted September 16, 2017 at 12:22 pm | Permalink

      If I recall correctly, that was in response to a competition of some sort. Ah, found it – the Adams Prize.

    • Posted September 19, 2017 at 11:48 am | Permalink

      I’ll have to check to see if any of my (popularizations and biographies) mention this connection: I do remember that he had calculated that the rings cannot be solid, but I don’t remember any details of how. I guess it is a bit too advanced for _Matter and Motion_ to even mention (if he’d done it by then).

  7. Genghis
    Posted September 16, 2017 at 11:15 am | Permalink

    We have seen the face of God: Saturn be praised!

    • gravelinspector-Aidan
      Posted September 16, 2017 at 12:34 pm | Permalink

      For you, Sithrak is oiling a stake, completely similar to the myriad of other stakes he makes. Sithrak is an angry, but scrupulously fair, god. My sucking up might have an effect on Oglaf, but Sithrak will be unmoved and I’ll get the same eternity of torment as everyone else.
      (Beware, while those links are “safe”, the rest of the web comic is … it has a certain direction.)

  8. Posted September 16, 2017 at 12:02 pm | Permalink

    Reblogged this on The Logical Place.

  9. gravelinspector-Aidan
    Posted September 16, 2017 at 12:42 pm | Permalink

    In other space news, there are rumours that New Horizons might have fuel to examine a third (or fourth) and even fourth (or fifth) Kuiper Belt object. The analysis of the data from July’s occultation by MU69 shows a lot of evidence for a bi-lobe shape (“rubber duck”, per comet 67P/Churyumov–Gerasimenko), or possibly even two objects in mutual orbit. But the light curve is pretty flat, suggesting that any rotation axis passes pretty close to our direction. Which means that planning to use New Horizon’s engines to try to get a better view is unlikely to be helpful. So, more fuel for a third encounter.
    Discussions continue. It is rumoured.

  10. Mark R.
    Posted September 16, 2017 at 12:58 pm | Permalink

    That was emotional. There was a photo in the Los Angeles Times showing some people at NASA crying. I can understand.

    • David Harper
      Posted September 16, 2017 at 2:17 pm | Permalink

      I made a small scientific contribution to the pre-launch planning of Cassini back in the early 1990s, and even I got emotional when loss-of-signal was announced yesterday. I can only imagine how it felt for the scientists and engineers who have spent their entire working lives on this mission.

      • Mark R.
        Posted September 16, 2017 at 7:21 pm | Permalink

        Indeed. All who worked on it (including you) should be (and I’m sure are) proud of this mighty accomplishment.

  11. Posted September 16, 2017 at 4:41 pm | Permalink

    Cassini’s been an amazing mission – an awesome amount of science, and an awesome collection of photos.

  12. Posted September 16, 2017 at 5:30 pm | Permalink

    In case your interested here is a pretty cool look at science’s graveyard (or is that junkyard) spread all over the solar system. No place is safe anymore but out there we must go.
    Commiserations to the Cassini team what a way to go and what a great job.

    JPL also released some neat downloadable posters for the Voyager I & II commemorations.

  13. eric
    Posted September 16, 2017 at 8:21 pm | Permalink

    I partly wish they had kept the camera on for the ride down. I know why they didn’t (it’s a data stream hog; you are trading away atmospheric and magnetic data to get it)…however, if you look at various lists of ‘top discoveries’, it seems to me that most of them are visual spectrum discoveries. Hexagonal storm? The camera. Enceladus’ eruptions? Visual. The ‘propellers?’ Visual.

    Now I’m sure a lot of good papers will come out of the last few minutes of data stream. But I wonder if more revolutionary discoveries would’ve come from the camera, even though it would’ve meant less overall data content.

  14. Posted September 19, 2017 at 11:50 am | Permalink

    _sic transit gloria mundi_, or rather worlds rather than world …

    Darwin’s “endless forms most beautiful” must be added to with those of the planetary scientists, I think.

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