APOD: Behind Saturn (2016 Aug 01)

[APOD Robot]

Behind Saturn

Explanation: What's behind Saturn? The first answer is the camera itself, perched on the Cassini spacecraft currently orbiting behind the planet with the most grand ring system in our Solar System. The unusual perspective places Cassini on the far side of Saturn from the Sun so that more than half of Saturn appears dark -- a perspective that no Earth-based observer could achieve. Behind Saturn, in the context of the featured infrared image, is Saturn's moon Tethys, visible as the small speck above the unusual hexagonal cloud pattern that encompasses Saturn's North Pole. Tethys actually orbits Saturn right in the ring plane, which places the 1000-km moon much farther from Cassini than the planet itself. Cassini has been studying Saturn and its moons for 12 years, but, unfortunately, its amazing mission will soon come to an end. In order to protect life that may exist on or inside Saturn's moons, the robotic spacecraft will be directed to crash into Saturn's thick atmosphere next September.

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[ShaileshS]

It's too difficult to imagine "Tethys actually orbits Saturn right in the ring plane". We can see it high above Sun's north pole, I agree, if it's toooooo far then it's possible that it's really in the same plane as rings but it's difficult to imagine and believe with this angle .. Right ? Thanks.

[geckzilla]

It's too difficult to imagine "Tethys actually orbits Saturn right in the ring plane". We can see it high above Sun's north pole, I agree, if it's toooooo far then it's possible that it's really in the same plane as rings but it's difficult to imagine and believe with this angle .. Right ? Thanks.

Cassini's camera has a tendency to flatten things out, perspective-wise. This is very confusing for a human whose eyes do not have the same optical characteristics that a telescope does. Notice, for example, that the front part of the rings do not look any larger than the back part of the rings. Humans are used to things in the foreground being bigger and things in the background being smaller. Our brain uses these contextual clues to build its model of reality. Unfortunately, it breaks down once those clues go missing.

[hardware dealer]

end the mission to saturn ??

why ??

the mission to saturn has been successful technically and should be allowed to continue for at least another five years after which time the space craft may be directed to return to the earth for terrestrial related work.

dumping a functional space probe for no reason is sheer insanity.

perhaps a glimpse of saturn cloud tops in a descending mode is desired. but the spaceprobe will eventually burn up in saturn's upper atmosphere preventing collection of adequate data. artists renderings have envisioned such vistas which may be generated by computer.

the reasonable thing to do would be to cancel other space exploration projects and allow the saturn mission to continue until such time as when e.t. aliens may be called upon to recover the spacecraft and return it to the earth.

if a space craft cannot be recovered then it should not be sent off. any space exploration project which relies on use and throw away of hardware is non sense and not science.

[Ann]

Imagine that Cassini has spent twelve years investigating Saturn and its rings and moons. I certainly agree that it has been well worth the money it has cost.

That's why I think it's a pity that Jupiter gets so little attention, and that the Juno mission will be so short. Jupiter is arguably the most "important" planet in the solar system, the one that influences its environment the most.

Ann

[heehaw]

if a space craft cannot be recovered then it should not be sent off.

Ummmm.... New Horizons?

[geckzilla]

end the mission to saturn ??

why ??

It's at the point where the probe's navigational fuel is nearly depleted. What you may not know is that Cassini performs many maneuvers around Saturn. It is not simply orbiting it along the same path over and over. They're using the last of it to get it to a safe spot. Safe for the environment around Saturn, that is. Can't have that pristine system mucked up with our microbes.

[Case]

end the mission to saturn? why?
[...] after which time the space craft may be directed to return to the earth for terrestrial related work.
dumping a functional space probe for no reason is sheer insanity. if a space craft cannot be recovered then it should not be sent off. any space exploration project which relies on use and throw away of hardware is non sense and not science.

Cassini is old tech by todays standards. It was launched in 1997, meaning the electronics tech used was probably many years older (design lockdown and testing). (Are you interested in buying my 28k8 modem that is gathering dust?) If you would recover the probe, you'd have a museum piece, not a modern functional satellite that anyone is willing to re-use. Recycling would be insane as well, as it isn't worth millions to recover just several hundred dollars of precious metals. The sensible thing to do with this project is in only returning signals (data), not the probe itself. The science is independent of how much hardware is left at the end of the project.

[Chopper]

Can someone explain why the cloud at Saturn's north pole has a hexagonal shape instead of circular?

[Case]

Can someone explain why the cloud at Saturn's north pole has a hexagonal shape instead of circular?

https://en.wikipedia.org/wiki/Saturn%27 ... xplanation
http://www.space.com/30608-mysterious-s ... ained.html

[Animal of Stone]

It seems to me that after we have finished exploring our neighbours we plunge our devices into them. Could they not be programmed to explode somewhere in deep space or directed away from our planets and into deep stellar space.

[Asterhole]

It seems to me that after we have finished exploring our neighbours we plunge our devices into them. Could they not be programmed to explode somewhere in deep space or directed away from our planets and into deep stellar space.

As stated before, Cassini is running low on fuel it uses for orbital maneuvers. To escape Saturn's gravity to a "safe spot" may impossible with what little of its fuel remains, so it could very well just loop back toward the planet and hit a moon along the way. I sure hate to see this trusty hard-working little probe come to such a ignoble end, but I guess it's safer that way.

[Fred the Cat]

What became of Emily's "crazy" idea? Will "plunging through a point just outside the narrow F ring (the edge of the main rings)" give more information about the rings? After re-reading the "The Grand Finale" perhaps that is the plan.

[Chris Peterson]

It seems to me that after we have finished exploring our neighbours we plunge our devices into them. Could they not be programmed to explode somewhere in deep space or directed away from our planets and into deep stellar space.

There is no way for a probe like this to get out of Saturn orbit. Gravitationally, it is essentially a part of Saturn. So the only viable option to avoid contamination of the system is to crash into that planet.

[Dustdreamer]

So the only viable option to avoid contamination of the system is to crash into that planet.

Why?
What would the problem be with trying to force the probe into so nearly a low polar orbit of Saturn as the remaining fuel can achieve? That way, Cassie can image Saturn and The Rings for us for a while and she will eventually drop to the "surface" of her own volition when atmospheric drag takes her down?

Also, has no one at NASA/JPL read "Encounter With Medusa", by Clarke? If they are imaginative enough to dream that alien bugs might live on Titan and Europa, Mimas and Io so Jovian and Saturnian orbiters must avoid those places, don't they consider that Jupiter and Saturn, too may have indigents?
I would.
Sure, burning up could crispy-fry everything terrestrial but it might not. Lumps might survive.
Do we really want to find Earthman-type bugs in the airs of Saturn in a few centuries?

Also, in the realm of "Trek" and "Dr. Who", refuelling tanker?

[Chris Peterson]

So the only viable option to avoid contamination of the system is to crash into that planet.

Why?
What would the problem be with trying to force the probe into so nearly a low polar orbit of Saturn as the remaining fuel can achieve? That way, Cassie can image Saturn and The Rings for us for a while and she will eventually drop to the "surface" of her own volition when atmospheric drag takes her down?

I don't think anybody is comfortable leaving a spacecraft in orbit that cannot be controlled. And FWIW, changing orbital eccentricity tends to be expensive. It's likely that putting Cassini into a nearly circular orbit well inside the ring system is either not possible with the remaining fuel, or would use so much that the remaining science mission would be impacted.

Also, has no one at NASA/JPL read "Encounter With Medusa", by Clarke? If they are imaginative enough to dream that alien bugs might live on Titan and Europa, Mimas and Io so Jovian and Saturnian orbiters must avoid those places, don't they consider that Jupiter and Saturn, too may have indigents?

Not a problem, because the entry velocity is so high that anything biological remaining on the craft will be completely burned away. Lumps will not survive. The same can't be said for crashing into a moon.

[Catalina]

How is NASA insuring that NO microbes are planted on Mars with all of the rovers making soft landings and cruising such distances on the martian surface?

[Chris Peterson]

How is NASA insuring that NO microbes are planted on Mars with all of the rovers making soft landings and cruising such distances on the martian surface?

They aren't. Because they can't. They do their best to sterilize what they can, but it's quite possible that some living microbes have made it to the surface of Mars. Luckily, that's a very inhospitable place for Earth life, so it's improbable that anything would survive long. But not impossible.

[ShaileshS]

How is NASA insuring that NO microbes are planted on Mars with all of the rovers making soft landings and cruising such distances on the martian surface?

They aren't. Because they can't. They do their best to sterilize what they can, but it's quite possible that some living microbes have made it to the surface of Mars. Luckily, that's a very inhospitable place for Earth life, so it's improbable that anything would survive long. But not impossible.

Who knows, maybe some would survive and 10-20 yrs down the road, folks visiting from earth would "discover" new life on Mars (yeah, right !) and some human beings will be elated (as in "Finally, we found LIFE somewhere else") and some would predict the doom soon (as in "This confirms there's aliens out there more intelligent than us who'd come and destroy us soon !"). No one knowing that time (or would realize that time) that these were left there (and survived) by our own missions 10-20 yrs back.

[Boomer12k]

They grow up sooooo fast....

But really...."TO PROTECT LIFE"?????????? Gimme a break.....

:---[===] *

[Dustdreamer]

if a space craft cannot be recovered then it should not be sent off.

Ummmm.... New Horizons?

Newby could be retrieved. All we need to do is slingshot her past her next target so she falls towards another falling rock then bounce her from rock to rock until one of the gravitational slingshots gives her an Earthward trajectory.
It might take a few centuries, and it would require us to find suitable rocks and ice-balls in appropriate orbits but those JPL guys are very, very good at this sort of stuff.
They got Voyager to Neptune using this technique, bouncing Newby around should be easy for them.

Chris is going to give us pages of why this is a ludicrous idea.

[Dustdreamer]

So the only viable option to avoid contamination of the system is to crash into that planet.

Why?
What would the problem be with trying to force the probe into so nearly a low polar orbit of Saturn as the remaining fuel can achieve? That way, Cassie can image Saturn and The Rings for us for a while and she will eventually drop to the "surface" of her own volition when atmospheric drag takes her down?

I don't think anybody is comfortable leaving a spacecraft in orbit that cannot be controlled. And FWIW, changing orbital eccentricity tends to be expensive. It's likely that putting Cassini into a nearly circular orbit well inside the ring system is either not possible with the remaining fuel, or would use so much that the remaining science mission would be impacted.

Also, has no one at NASA/JPL read "Encounter With Medusa", by Clarke? If they are imaginative enough to dream that alien bugs might live on Titan and Europa, Mimas and Io so Jovian and Saturnian orbiters must avoid those places, don't they consider that Jupiter and Saturn, too may have indigents?

Not a problem, because the entry velocity is so high that anything biological remaining on the craft will be completely burned away. Lumps will not survive. The same can't be said for crashing into a moon.

Cool, thanks, but what about a refuelling tanker? Maybe with some updated electronics boxes and a better camera?

Yes, I know, Cassini-2 would be faster and vastly cheaper and would give us more Science. But it's a shame that we have to keep expending these robots when they have given us so much.

I just had a brilliant idea ... something truly amazing and paradigm shattering ... we could send a human engineer to update and refuel Cassie.
I volunteer.
I'll even supply my own screwdriver sets.

[geckzilla]

Please stop anthropomorphizing spacecraft and using feminine pronouns. They're not women.

[Dustdreamer]

Please stop anthropomorphizing spacecraft and using feminine pronouns. They're not women.

True, they are not women, they are not even alive. However, they are either ships or aircraft and both of those are, by tradition, commonly referred to with the feminine pronoun in English.
Even ships with masculine names, such as U. S. S. Nimitz and which are actually named after masculine humans, such as Admiral Nimitz, are considered to be female -ish.
The robots we drop around, onto and into planets and moons are spaceships - a type of ship, or unmanned aerial vehicles - a type of heavier than air flying machine, both of which classes of instrumentality are usually give feminine pronouns.
It has nothing to do with anthropomorphism, it is simply a correct use of the language.

Planets, stars, galaxies, moons and even the falling rocks variously termed "Asteroids", "Minor Planets" or "Dwarf Planets" are also feminine, even those, such as Jupiter, whose names are most certainly male. Even countries and cities can be female.

It's a thing. Don't blame me for it, I only live here I didn't design the language. English, she is a law unto herself.

[geckzilla]

It's a thing. Don't blame me for it, I only live here I didn't design the language. English, she is a law unto herself.

You're the only one here doing it. It's long been officially deprecated. Stop.