APOD: Saturn's Rings from the Inside Out (2017 Sep 04)

[APOD Robot]

Saturn's Rings from the Inside Out

Explanation: What do Saturn's rings look like from Saturn? Images from the robotic spacecraft Cassini are providing humanity with this unprecedented vantage point as it nears the completion of its mission. Previous to Cassini's Grand Finale orbits, all images of Saturn's majestic ring system were taken from outside of the rings looking in. Pictured in the inset is the remarkable video, while the spacecraft's positions are depicted in the surrounding animation. Details of the complex rings are evident as the short time-lapse sequence begins, while the paper-thin thickness of the rings becomes apparent near the video's end. The featured images were taken on August 20. Cassini has only a few more orbits around Saturn left before it is directed to dive into the giant planet on September 15.

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[distefanom]

I wonder WHY they left the Cassini Probe whizzing around Saturn for so many years, actually so far away from saturn, and they NEVER thought to put in a stable Inside-outside ring's orbit to have to possibility -over years- to map Saturn "surface" evolution down to the kilometer (if not even more) feature and also (maybe) it's the planetary system.
I think these latest images are a scientific well of information for the future.
If not for tech reasons I don't know, It's sad not have done it before!

[geckzilla]

I wonder WHY they left the Cassini Probe whizzing around Saturn for so many years, actually so far away from saturn, and they NEVER thought to put in a stable Inside-outside ring's orbit to have to possibility -over years- to map Saturn "surface" evolution down to the kilometer (if not even more) feature and also (maybe) it's the planetary system.
I think these latest images are a scientific well of information for the future.
If not for tech reasons I don't know, It's sad not have done it before!

It was too dangerous to risk the craft at any point earlier in the mission.

[Boomer12k]

Outstanding view... interesting animation...

:---[===] *

[heehaw]

I am still annoyed that they did not have Cassini simply gently become a particle in one of the rings. We'd have seen a ring from inside!

[distefanom]

Hi geckzilla
Due to the longevity of the spacecraft (it started in 1998!!!) I think a way longer "retirement plan" could be made.
Just as every probe space mission, I think "the nearer, the better" is a key factor to get valuable, precise and accurate data from the spacecraft itself.
This is the main reason, NASA sends things like Opportunity, Curiosity, Spirit rovers... to have the BEST quality data, from any mission.
I think Cassini has been neglected from it's own capabilities....
The same has been for the Huygens probe... Why make a probe who could survive that harsh environment only for 90 minutes....
It's pitiable at least...

[geckzilla]

Hi geckzilla
Due to the longevity of the spacecraft (it started in 1998!!!) I think a way longer "retirement plan" could be made.
Just as every probe space mission, I think "the nearer, the better" is a key factor to get valuable, precise and accurate data from the spacecraft itself.
This is the main reason, NASA sends things like Opportunity, Curiosity, Spirit rovers... to have the BEST quality data, from any mission.
I think Cassini has been neglected from it's own capabilities....
The same has been for the Huygens probe... Why make a probe who could survive that harsh environment only for 90 minutes....
It's pitiable at least...

I just kinda trust that the people who have been with Cassini all this time are professionals and know better than any of us. They said Cassini's navigation fuel has run out, and the best outcome to preserve the Saturn system is to deorbit. I believe them. The rationale is sound. I couldn't do better. I don't think anyone could.

[HellCat]

The same has been for the Huygens probe... Why make a probe who could survive that harsh environment only for 90 minutes....

You make a probe to accomplish its mission, with some allowance for a margin of safety. Going any further adds time and cost, and probably weight. NASA doesn't get enough money to do as much as it could.

Ring insertion would have been "fun" but NASA is overly concerned with contaminating other possible ecosystems. Apparently the chances of hitting a Saturnian on the head is less than infecting Enceladas or Tethys with E. coli or Zika.

[heehaw]

The same has been for the Huygens probe... Why make a probe who could survive that harsh environment only for 90 minutes....
It's pitiable at least...

I am happy to say that we may be going BACK to Titan, this time to use a quadcopter to explore and analyze that fascinating world...
http://www.jhuapl.edu/newscenter/pressr ... 170823.asp

[Ann]

Why make a probe who could survive that harsh environment only for 90 minutes....
It's pitiable at least...

I don't agree with you at all. I think the Cassini mission has been a stunning success. To pull all of this off is not pitiable, it's fabulous!

What makes you think it is easy to send not just a superbly functioning probe to Saturn, but a probe that could keep functioning for much longer than its fuel will allow, and a probe that is sturdy enough to sink deep into the atmosphere of Saturn and return data to the Earth all the time?

Do you really think that would be easy? Do you really think that NASA's Cassini mission is not a success?

Ann

[neufer]

Due to the longevity of the spacecraft (it started in 1998!!!) I think a way longer "retirement plan" could be made.
Just as every probe space mission, I think "the nearer, the better" is a key factor to get valuable, precise and accurate data from the spacecraft itself. The same has been for the Huygens probe... Why make a probe who could survive that harsh environment only for 90 minutes....It's pitiable at least...

[img3="Chronos and his child by Giovanni Francesco Romanelli, National Museum in Warsaw, a 17th century depiction of Titan Cronus/Saturn as "Father Time," wielding a harvesting scythe"]https://upload.wikimedia.org/wikipedia/ ... _child.jpg[/img3]

<<Chronos (Greek: Χρόνος, "time", Latinised as Chronus) is the personification of Time in pre-Socratic philosophy and later literature. Chronos governed linear, chronological time. The other Greek word for time is kairos, meaning the indeterminate moment that is right for something to occur. The original meaning and etymology of the word chronos are uncertain. Some of the current English words whose etymological root is khronos/chronos include chronology, chronometer, chronic, anachronism, and chronicle.

Chronos already was confused with, or perhaps consciously identified with, the Titan Cronus/Saturn in antiquity due to the similarity in names. The identification became more widespread during the Renaissance, giving rise to the allegory of "Father Time" wielding the harvesting scythe. In addition to the name, the story of Cronus eating his children was also interpreted as an allegory to a specific aspect of time held within Cronus' sphere of influence.

As the theory went, Cronus represented the destructive ravages of time which consumed all things, a concept that was definitely illustrated when the Titan king devoured the Olympian gods — the past consuming the future, the older generation suppressing the next generation. During the Renaissance, the identification of Cronus and Chronos gave rise to "Father Time" wielding the harvesting scythe.>>

[distefanom]

I'm not saying that one could do it better than NASA; I simply can't, since I'm not a scientist NASA director...
I'm only saying it could have been done a bit DIFFERENTLY.
If you think that a hitch to those places is not a thing that happens everyday (1998!!!), why not "stuff" more things is possible on a mission?
A longer living Huygens probe, won't mean necessarily more weight, maybe only MORE FUNDS...
I THINK this IS THE MAIN PROBLEM.... EVER!
HellCat is right stating this...
I dont' mean that smashing Cassini in saturn is safer than hitting a Saturnian on Saturn's moon.
But if we are afraid to infect... we should NEVER go anywhere.... Instead we *are LITTERING* planets with malfunctioning probes...
because we usually play "passing the buck" when it comes to "international cooperations"

[MarkBour]

I agree, this is a remarkable video. It was a great idea to use one of the last orbits to capture that view. I was a little disappointed that the rings did not stay in frame a little longer, to get a good comparative view of their darker side. But I'll bet Cassini could not have rotated its camera any faster than it was doing, which makes this a very fine piece of photography -- I think it was balanced beautifully for the brief pass as well as possible (and therefore, that probably took some planning). Besides, I'll bet the scientists already have plenty of images of Saturn's rings from both sides if they wanted to determine reflectivity / opacity or whatever. And I agree with Ann, this has been an amazingly successful mission.

I am happy to say that we may be going BACK to Titan, this time to use a quadcopter to explore and analyze that fascinating world...
http://www.jhuapl.edu/newscenter/pressr ... 170823.asp

Thanks for sharing that, heehaw, looks like a fascinating mission plan. I wonder what the competition will dream up?

Although this is just really ambitious thinking, I assume that eventually we have to begin thinking more long-term? What are the chances, in the next couple of decades, of sending a mission to another planet that could actually

• obtain fuel on-site
• self-repair
• provide an asset that additional probes could re-use

so that not every launch into deep space needs to carry everything it needs in one package?

[neufer]

• James Clerk Maxwell on the nature of Saturn's rings

<<In 1859 James Clerk Maxwell published On the Stability of the Motion of Saturn's Rings. Maxwell was awarded the Adams Prize for his essay which contained many pages of detailed mathematical calculations [and concluded thusly]:

... Let us now gather together the conclusions we have been able to draw from the mathematical theory of various kinds of conceivable rings.

We found that the stability of the motion of a solid ring depended on so delicate an adjustment, and at the same time so unsymmetrical a distribution of mass, that even if the exact condition were fulfilled, it could scarcely last long, and if it did, the immense preponderance of one side of the ring would be easily observed, contrary to experience. These considerations, with others derived from the mechanical structure of so vast a body, compel us to abandon any theory of solid rings.

We next examined the motion of a ring of equal satellites, and found that if the mass of the planet is sufficient, any disturbances produced in the arrangement of the ring will be propagated round it in the form of waves, and will not introduce dangerous confusion. If the satellites are unequal, the propagation of the waves will no longer be regular, but disturbances of the ring will in this, as in the former case, produce only waves, and not growing confusion. Supposing the ring to consist, not of a single row of large satellites, but of a cloud of evenly distributed unconnected particles, we found that such a cloud must have a very small density in order to be permanent, and that this is inconsistent with its outer and inner parts moving with the same angular velocity. Supposing the ring to be fluid and continuous, we found that it will be necessarily broken up into small portions.

We conclude, therefore, that the rings must consist of disconnected particles; these may be either solid or liquid, but they must be independent. The entire system of rings must therefore consist either of a series of many concentric rings, each moving with its own velocity, and having its own systems of waves, or else of a confused multitude of revolving particles, not arranged in rings, and continually coming into collision with each other.

...Finally, the two outer rings have been observed for 200 years, and it appears, from the careful analysis of all the observations by Struve, that the second ring is broader than when first observed, and that its inner edge is nearer the planet than formerly. The inner ring also is suspected to be approaching the planet ever since its discovery in 1850. These appearances seem to indicate the same slow progress of the rings towards separation which we found to he the result of theory, and the remark, that the inner edge of the inner ring is most distinct, seems to indicate that the approach towards the planet is less rapid near the edge, as we had reason to conjecture. As to the apparent unchangeableness of the exterior diameter of the outer ring, we must remember that the outer rings are certainly far more dense than the inner one, and that a small change in the outer rings must balance a great change in the inner one. It is possible, however, that some of the observed changes may be due to the existence of a resisting medium. If the changes already suspected should be confirmed by repeated observations with the same instruments, it will be worth while to investigate more carefully whether Saturn's Rings are permanent or transitionary elements of the Solar System, and whether in that part of the heavens we see celestial immutability, or terrestrial corruption and generation, and the old order giving place to new before our own eyes.>>

[Enoch Hammerslob]

Does anyone know if there are plans to watch Cassini make it's swan dive from any of the large earth based observatories? Will it even be visible from earth, for that matter?

[neufer]

Does anyone know if there are plans to watch Cassini make it's swan dive from any of the large earth based observatories? Will it even be visible from earth, for that matter?

No plans to watch Cassini make it's belly-flop from any of the large earth based observatories as it won't even be visible from Earth, for that matter.

[Enoch Hammerslob]

Does anyone know if there are plans to watch Cassini make it's swan dive from any of the large earth based observatories? Will it even be visible from earth, for that matter?

No plans to watch Cassini make it's belly-flop from any of the large earth based observatories as it won't even be visible from Earth, for that matter.

https://commons.wikimedia.org/wiki/File ... 170915.jpg