APOD: Over Saturn's Turbulent North Pole (2016 Dec 12)

[APOD Robot]

Over Saturn's Turbulent North Pole

Explanation: The Cassini spacecraft's Grand Finale at Saturn has begun. The Grand Finale will allow Cassini to explore Saturn and some of Saturn's moons and rings in unprecedented detail. The first phase started two weeks ago when a close flyby of Titan changed Cassini's orbit into one that passes near Saturn's poles and just outside of Saturn's outermost F-ring. Featured here is an image taken during the first of Cassini's 20 week-long F-ring orbits around Saturn. Visible are the central polar vortex on the upper left, a hexagonal cloud boundary through the image center, and numerous light-colored turbulent storm systems. In 2017 April, Cassini will again use the gravity of Titan to begin a new series of 22 Proximal orbits -- trajectories that will take Cassini inside of Saturn's rings for the first time. Cassini's new science adventure is scheduled to end on 2017 September 17, though, when the robotic spacecraft will be directed into a dramatic mission-ending dive into Saturn's atmosphere.

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[Curious22]

Isn't there a (remote) risk of contaminating Saturn with 'alien' metals, materials and even bugs when Cassini is ordered into Saturns atmosphere ?

[Chris Peterson]

Isn't there a (remote) risk of contaminating Saturn with 'alien' metals, materials and even bugs when Cassini is ordered into Saturns atmosphere ?

There are no elements present in Cassini that aren't already in Saturn. And the energy released when Cassini burns up will certainly vaporize anything alive.

[JohnD]

I read that while as Chris says, it would make no difference to Saturn, crashing it into a satellite could be the reverse, and leaving it in orbit is just vandalism!
John

[heehaw]

Isn't there a (remote) risk of contaminating Saturn with 'alien' metals, materials and even bugs when Cassini is ordered into Saturns atmosphere ?

There are no elements present in Cassini that aren't already in Saturn. And the energy released when Cassini burns up will certainly vaporize anything alive.

I wonder about that: stuff knocked off Mars has landed in Antarctica (and of course elsewhere more congenial to life) with complex chemicals intact! Most interesting, would be for us to deliberately seed the atmosphere of Venus with microbes that would convert all the CO2 to O2 which would remove the greenhouse effect and make Venus a candidate for human colonization.

[JohnD]

"Life" on Earth has had more opportunity to diversify than on Mars. It seems likely that a Martian organism would be overwhelmed by things evolved to grow faster and to take advantage of more plentiful resources. While the opposite would be true, but we want to know if there was anything there in the first place, not adapted Earth germs.

Terraforming should surely take place AFTER we know the native ecology, or lack of it.

JOhn

[saturno2]

Cassini into Saturn´s atmosphere
It is a " impossible mission "

[JohnD]

Why?

[heehaw]

Most interesting, would be for us to deliberately seed the atmosphere of Venus with microbes that would convert all the CO2 to O2 which would remove the greenhouse effect and make Venus a candidate for human colonization.

Oops, I googled a bit: unfortunately Venus is "bone dry." Without water, the microbes would be extinct very quickly. Oh well! We humans seem to have nowhere to go except a) asteroid (but why?) b) Mars (you can go; not me! And again, not nearly enough water even if there are aquifers here and there) c) our own Moon once again. On that last, I have a question: would a nuclear electric generator have cooling problems being in direct sunlight for two solid weeks? Maybe it is not a problem; there is still dark sky to radiate excess heat to. Launching a nuclear plant would have been a no-no before, but maybe after January 20 it could happen. I must say I'd kind of like it!

[BobStein-VisiBone]

Really hoping we get to see a closeup of the actual rings, and to finally obsolete all those "artists renderings" we've had to put up with forever.

[Chris Peterson]

Isn't there a (remote) risk of contaminating Saturn with 'alien' metals, materials and even bugs when Cassini is ordered into Saturns atmosphere ?

There are no elements present in Cassini that aren't already in Saturn. And the energy released when Cassini burns up will certainly vaporize anything alive.

I wonder about that: stuff knocked off Mars has landed in Antarctica (and of course elsewhere more congenial to life) with complex chemicals intact!

Saturn is a factory for complex organic molecules. There's nothing on Cassini that Saturn isn't making somewhere.

[appz]

Are these circles 3 dimensional? Are they deep vortexs like a funnel or are the just flat spinning things?

[Seaquest]

"Life" on Earth has had more opportunity to diversify than on Mars. It seems likely that a Martian organism would be overwhelmed by things evolved to grow faster and to take advantage of more plentiful resources. While the opposite would be true, but we want to know if there was anything there in the first place, not adapted Earth germs.

Terraforming should surely take place AFTER we know the native ecology, or lack of it.

JOhn

We are certainly terraforming earth making it habitable for alien lifeforms adopted to toxic environments. Maybe they're in charge of business, politics and the family home down here?

[MarkBour]

Really hoping we get to see a closeup of the actual rings, and to finally obsolete all those "artists renderings" we've had to put up with forever.

I loved your 7th rendering image.

[Curious22]

There are no elements present in Cassini that aren't already in Saturn. And the energy released when Cassini burns up will certainly vaporize anything alive.

Cassini is powered by a plutonium generator, 33kg of it in fact. !!
Do we KNOW that there is plutonium in Saturns atmosphere, or on Saturn itself ??
(if there is a solid surface in there anywhere) ?.

Wasn't it quipped that if the Cassini launch vehicle had failed in earths atmosphere, the consequences could have been pretty dire.
And plutonium, in any quantity, has only appeared on earth since nuclear weapons testing proliferated.
??

[Chris Peterson]

There are no elements present in Cassini that aren't already in Saturn. And the energy released when Cassini burns up will certainly vaporize anything alive.

Cassini is powered by a plutonium generator, 33kg of it in fact. !!
Do we KNOW that there is plutonium in Saturns atmosphere, or on Saturn itself ??
(if there is a solid surface in there anywhere) ?.

There is certainly plutonium in Saturn's atmosphere in trace amounts (and another 33 kg distributed over its atmosphere is just a trace of a trace). There is uranium everywhere in the solar system, and there are natural mechanisms which result in the conversion of U to Pu. (And there is a surface of sorts on Saturn- a core.)

Wasn't it quipped that if the Cassini launch vehicle had failed in earths atmosphere, the consequences could have been pretty dire.

Not really. One reason we allow ourselves to launch RTGs is because even if they fail catastrophically, the consequences are not large.

And plutonium, in any quantity, has only appeared on earth since nuclear weapons testing proliferated.
??

No, Pu appears as a natural trace element on Earth, too. And the Pu-238 used with the RTG has a very short half-life, just 88 years. And to the extent it presents any danger, it's to lifeforms, which are very unlikely on Saturn.

The bottom line is that the probe represents no appreciable risk to Saturn or our future studies of Saturn, but could potentially contaminate one of the much smaller moons enough to interfere with future research in those places.

[neufer]

Are these circles 3 dimensional? Are they deep vortexs like a funnel or are the just flat spinning things?

• The central vortex is probably relatively deep.

[b][color=#0000FF]Closer view of the large northern vortex inside the hexagon on Saturn.[/color][/b]

---

<<Saturn's hexagon is a persisting hexagonal cloud pattern around the north pole of Saturn, located at about 78°N. The sides of the hexagon are about 13,800 km long, which is more than the diameter of Earth (about 12,700 km). It rotates with a period of 10h 39m 24s, the same period as Saturn's radio emissions from its interior. The hexagon does not shift in longitude like other clouds in the visible atmosphere.

Saturn's south pole does not have a hexagon, according to Hubble observations; however, it does have a vortex, and there is also a vortex inside the northern hexagon.

Saturn's polar hexagon discovery was made by the Voyager mission in 1981–82, and it was revisited since 2006 by the Cassini mission. Cassini was only able to take thermal infrared images of the hexagon, until it passed into sunlight in January 2009. Cassini was also able to take a video of the hexagonal weather pattern while traveling at the same speed as the planet, therefore recording only the movement of the hexagon. After its discovery, and after it came back into the sunlight, amateur astronomers managed to get images showing the hexagon from Earth.

One hypothesis, developed at Oxford University, is that the hexagon forms where there is a steep latitudinal gradient in the speed of the atmospheric winds in Saturn's atmosphere. Similar regular shapes were created in the laboratory when a circular tank of liquid was rotated at different speeds at its centre and periphery. The most common shape was six sided, but shapes from three to eight sided were also produced. The shapes form in an area of turbulent flow between the two different rotating fluid bodies with dissimilar speeds. A number of stable vortices of similar size form on the slower (south) side of the fluid boundary and these interact with each other to space themselves out evenly around the perimeter. The presence of the vortices influences the boundary to move northward where each is present and this gives rise to the polygon effect. Polygons do not form at wind boundaries unless the speed differential and viscosity parameters are within certain margins and so are not present at other likely places, such as Saturn's south pole or the poles of Jupiter.>>

[neufer]

Wasn't it quipped that if the Cassini launch vehicle had failed in earths atmosphere,
the consequences could have been pretty dire.

Not really. One reason we allow ourselves to launch RTGs is because
even if they fail catastrophically, the consequences are not large.

<<The failure of the Apollo 13 mission in April 1970 meant that the Lunar Module reentered the atmosphere carrying an RTG and burned up over Fiji. It carried a SNAP-27 RTG containing 44,500 Ci of plutonium dioxide in a graphite cask on the lander leg which survived reentry into the Earth's atmosphere intact, as it was designed to do, the trajectory being arranged so that it would plunge into 6–9 kilometers of water in the Tonga trench in the Pacific Ocean. The absence of plutonium-238 contamination in atmospheric and seawater sampling confirmed the assumption that the cask is intact on the seabed. The cask is expected to contain the fuel for at least 10 half-lives (i.e. 870 years). The US Department of Energy has conducted seawater tests and determined that the graphite casing, which was designed to withstand reentry, is stable and no release of plutonium should occur. Subsequent investigations have found no increase in the natural background radiation in the area. The Apollo 13 accident represents an extreme scenario because of the high re-entry velocities of the craft returning from cis-lunar space. This accident has served to validate the design of later-generation RTGs as highly safe.>>

And plutonium, in any quantity,
has only appeared on earth since nuclear weapons testing proliferated??

No, Pu appears as a natural trace element on Earth, too.

[Chris Peterson]

<<The failure of the Apollo 13 mission in April 1970 meant that the Lunar Module reentered the atmosphere carrying an RTG and burned up over Fiji. It carried a SNAP-27 RTG containing 44,500 Ci of plutonium dioxide in a graphite cask on the lander leg which survived reentry into the Earth's atmosphere intact, as it was designed to do, the trajectory being arranged so that it would plunge into 6–9 kilometers of water in the Tonga trench in the Pacific Ocean. The absence of plutonium-238 contamination in atmospheric and seawater sampling confirmed the assumption that the cask is intact on the seabed. The cask is expected to contain the fuel for at least 10 half-lives (i.e. 870 years). The US Department of Energy has conducted seawater tests and determined that the graphite casing, which was designed to withstand reentry, is stable and no release of plutonium should occur. Subsequent investigations have found no increase in the natural background radiation in the area. The Apollo 13 accident represents an extreme scenario because of the high re-entry velocities of the craft returning from cis-lunar space. This accident has served to validate the design of later-generation RTGs as highly safe.>>

I think we can safely assume, however, that the Cassini RTG casing will fail during entry. (And the RTG safety analysis does include the possibility of a casing failure at launch, even though such a failure is very unlikely.)

[DavidLeodis]

In the explanation it states "Cassini's new science adventure is scheduled to end on 2017 September 17". I wonder if the 17 in "September 17" is a typing error as in information brought up from links in the explanation and elsewhere it states the mission will end on September 15 2017 . The date does not seem to be a time zone difference as the end date is reported to be on September 15 2017 even under Universal Time.

[Chris Peterson]

In the explanation it states "Cassini's new science adventure is scheduled to end on 2017 September 17". I wonder if the 17 in "September 17" is a typing error as in information brought up from links in the explanation and elsewhere it states the mission will end on September 15 2017 :?. The date does not seem to be a time zone difference as the end date is reported to be on September 15 2017 even under Universal Time.

All official indications are that the data collection part of the mission will end when Cassini hits Saturn's atmosphere at UT 2017.09.15 12:07.

[DavidLeodis]

In the explanation it states "Cassini's new science adventure is scheduled to end on 2017 September 17". I wonder if the 17 in "September 17" is a typing error as in information brought up from links in the explanation and elsewhere it states the mission will end on September 15 2017 . The date does not seem to be a time zone difference as the end date is reported to be on September 15 2017 even under Universal Time.

<br abp="372">All official indications are that the data collection part of the mission will end when Cassini hits Saturn's atmosphere at UT 2017.09.15 12:07.

Thanks Chris . Your help continues to be much appreciated.

[BobStein-VisiBone]

...all those "artists renderings"....

I loved your 7th rendering image.

The best fake news would be simultaneously horrible, and so effing interesting, if it were true.