APOD: Juno Approaching Jupiter (2016 Jul 01)

[BMAONE23]

Perhaps we'll be fortunate enough for Juno to have a ringside seat for the next Jovian Impactor

[Nitpicker]

Juno itself, might be the next significant Jovian impactor.

[neufer]

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Juno itself, might be the next significant Jovian impactor.

[Chris Peterson]

Juno itself, might be the next significant Jovian impactor.

Given its mission length, it will not be the next impactor (unless something goes terribly wrong!) And given its mass, it will never be a significant impactor.

[neufer]

Juno itself, might be the next significant Jovian impactor.

Given its mission length, it will not be the next impactor (unless something goes terribly wrong!) And given its mass, it will never be a significant impactor.

• That sort of depends upon one's definition of "significant."

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<<"If a tree falls in a forest and no one is around to hear it, does it make a sound?"

Philosopher George Berkeley, in his work, A Treatise Concerning the Principles of Human Knowledge (1710), proposes, "But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park [...] and nobody by to perceive them. [...] The objects of sense exist only when they are perceived; the trees therefore are in the garden [...] no longer than while there is somebody by to perceive them."

Some years later, a similar question is posed. It is unknown whether the source of this question is Berkeley or not. In June 1883 in the magazine The Chautauquan, the question was put, "If a tree were to fall on an island where there were no human beings would there be any sound?" They then went on to answer the query with, "No. Sound is the sensation excited in the ear when the air or other medium is set in motion." This seems to imply that the question is posed not from a philosophical viewpoint, but from a purely scientific one. The magazine Scientific American corroborated the technical aspect of this question, while leaving out the philosophic side, a year later when they asked the question slightly reworded, "If a tree were to fall on an uninhabited island, would there be any sound?" And gave a more technical answer, "Sound is vibration, transmitted to our senses through the mechanism of the ear, and recognized as sound only at our nerve centers. The falling of the tree or any other disturbance will produce vibration of the air. If there be no ears to hear, there will be no sound."

Albert Einstein is reported to have asked his fellow physicist and friend Niels Bohr, one of the founding fathers of quantum mechanics, whether he realistically believed that 'the moon does not exist if nobody is looking at it.' To this Bohr replied that however hard he (Einstein) may try, he would not be able to prove that it does, thus giving the entire riddle the status of a kind of an infallible conjecture—one that cannot be either proved or disproved.>>

[Fred the Cat]

I suppose the mime might make a sound though. "Timbre!"

[Chris Peterson]

Given its mission length, it will not be the next impactor (unless something goes terribly wrong!) And given its mass, it will never be a significant impactor.

• That sort of depends upon one's definition of "significant."

Okay. I'll take "significant" as at least energetic enough to be seen from Earth by sub-meter class telescopes. That means asteroidal bodies on the order of 10 meters or larger. Probably, there are several dozen such impact each year on Jupiter.

[Ann]

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Juno itself, might be the next significant Jovian impactor.

What!! Who'da thunk that Donald Trump looked so much like Jupiter, or is it the other way round?

Ann

[Chris Peterson]

What!! Who'da thunk that Donald Trump looked so much like Jupiter, or is it the other way round?

Wow. You managed to simultaneously insult Jupiter and compliment Trump!

[Ann]

What!! Who'da thunk that Donald Trump looked so much like Jupiter, or is it the other way round?

Wow. You managed to simultaneously insult Jupiter and compliment Trump!

Well, Trump doesn't look like Jupiter in real life, but in that cartoon, with his one Great Not-Exactly-Red Eye, he was a semi-dead ringer for it.

Ann

[JohnD]

Surely, neufer, you know of Ronald Knox's rey to Bishop Berkeley?
There once was a man who said, "God,
Must find it exceedly odd
To think that the tree
Should continue to be
When there' s no one about in the Quad"

"But dear Sir, your astonishment's odd
I am always about in the Quad
And that's why the tree
Will continue to be
Since observed by, yours faithfully, God."

A more cogent expression of the doctrine of omnipresence would be difficult to find.
John

[Nitpicker]

Given its mission length, it will not be the next impactor (unless something goes terribly wrong!) And given its mass, it will never be a significant impactor.

• That sort of depends upon one's definition of "significant."

Okay. I'll take "significant" as at least energetic enough to be seen from Earth by sub-meter class telescopes. That means asteroidal bodies on the order of 10 meters or larger. Probably, there are several dozen such impact each year on Jupiter.

I would class Juno as a significant impactor, on the basis that it is made and controlled by humans. For other, natural impactors, I was thinking they'd need to be much larger, and hence rarer, for me to deem them significant (i.e. the kind that I might be able to observe with my 6 inch telescope in the backyard, or that I might read about in the daily news). So yes, my statement depends entirely on the definition of "significant". But given it was my statement, I should also be allowed to define the terms of reference.

[Chris Peterson]

• That sort of depends upon one's definition of "significant."

Okay. I'll take "significant" as at least energetic enough to be seen from Earth by sub-meter class telescopes. That means asteroidal bodies on the order of 10 meters or larger. Probably, there are several dozen such impact each year on Jupiter.

I would class Juno as a significant impactor, on the basis that it is made and controlled by humans. For other, natural impactors, I was thinking they'd need to be much larger, and hence rarer, for me to deem them significant (i.e. the kind that I might be able to observe with my 6 inch telescope in the backyard, or that I might read about in the daily news). So yes, my statement depends entirely on the definition of "significant". But given it was my statement, I should also be allowed to define the terms of reference. :P

No argument. With natural Jupiter impactors having been in the news the last couple of years (and, of course, SL9 a couple of decades back), that's where my mind went.

That said, unless you restrict your definition of "significant" to man-made objects, however, Juno is very unlikely to be the next significant impactor. Or so we hope!

[Nitpicker]

Yes, a bit pessimistic of me. But I did say "might be" and not "will be", in regards to Juno being the next significant impactor.

(I have never observed an impactor strike Jupiter with my wee telescope. Though last weekend, I set it up for the first time in too long, and watched Ganymede's shadow pass across the Jovian surface, with amazing clarity. I'm still quite amazed that I've never had to collimate my scope after about 4 years of ownership.)

[neufer]

That said, unless you restrict your definition of "significant" to man-made objects, however, Juno is very unlikely to be the next significant impactor. Or so we hope!

Like the proverbial tree, a "significant" event is simply one of which humans are aware.

[MarkBour]

However, for a good view of Saturn's rings one really needs to be on a high inclination satellite like Siarnaq or Albiorix.

Thanks for the interesting data on these two moons. It appears that these little guys are not tidally locked. For the scenario I imagined to arise, one would have to have a large enough moon that people lived on one side of it and had never travelled to the planet-facing side until their society's mobility increased.

You bring up an interesting point that if they grew up on either Titan or Dione, then when they finally walked around, they'd not get a good view of the rings. But as you immediately pointed out as well, they would have the ring shadows for additional contemplation. I am finding this an equally fascinating question, actually, of how it would impact such a people to first view Saturn from a position that was precisely in the ring plane! They'd see a strange, thin, perfectly straight line bisecting the grand orb and extending beyond it. What religious debates would it induce? How much time would go by before some genius like Galileo explained that the shadows were shadows of the line? I think even people as sophisticated as our modern-day scientists would have had a hard time sorting that out and believing it, let alone humans from the year 1500.

I see a recent Cassini APOD that makes your point perfectly: http://apod.nasa.gov/apod/ap150824.html.

I guess I'm leaving out the other evidence that could have come their way by this point, if such a civilization developed similarly to ours. In the case of a moon of Jupiter or Saturn, if they had astronomers by that point, they would have been able to observe motions of many sister moons, and to wonder about them. Possibly they would even have put a fair number of their more intelligent folk to death by this point.

[neufer]

Of course, Titanians would probably have evolved near-infrared eyes.

Heh, yeah, that would probably be rather advantageous.

<<According to the Cornell research team – which is led by Dr. Martin Rahm – Titan presents an opportunity to see how life could emerge... which are much colder than Earth and don’t involve water. Previous experiments have shown that hydrogen cyanide (HCN) molecules can link together to form polyimine, a polymer that can serve as a precursor to amino acids and nucleic acids. Previous surveys have also shown that hydrogen cyanide is the most abundant hydrogen-containing molecule in Titan’s atmosphere.

Using quantum mechanical calculations, the Cornell team showed that polyimine has electronic and structural properties that could facilitate prebiotic chemistry under very cold conditions. These involve the ability to absorb a wide spectrum of light, which is predicted to occur in a window of relative transparency in Titan’s atmosphere.

“Polyimine can form sheets,” said Lunine, “which like clays might serve as a catalytic surface for prebiotic reactions. We also find the polyimine absorbs sunlight where Titan’s atmosphere is quite transparent, which might help to energize reactions.”>>

[neufer]

You bring up an interesting point that if they grew up on either Titan or Dione, then when they finally walked around, they'd not get a good view of the rings. But as you immediately pointed out as well, they would have the ring shadows for additional contemplation. I am finding this an equally fascinating question, actually, of how it would impact such a people to first view Saturn from a position that was precisely in the ring plane! They'd see a strange, thin, perfectly straight line bisecting the grand orb and extending beyond it. What religious debates would it induce? How much time would go by before some genius like Galileo explained that the shadows were shadows of the line? I think even people as sophisticated as our modern-day scientists would have had a hard time sorting that out and believing it, let alone humans from the year 1500.

I doubt that a Titanian "Galileo" would have any more to say about the rings than, perhaps:

• smaismrmilmepoetaleumibunenugttauiras.

[b][color=#0000FF]Robert Hooke noted the shadows (a and b) cast by both the globe and the rings on each other in this 1666 drawing of Saturn.[/color][/b]

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<<Galileo Galilei was the first to observe the rings of Saturn in 1610 using his telescope, but was unable to identify them as such. He wrote to the Duke of Tuscany that "[t]he planet Saturn is not alone, but is composed of three, which almost touch one another and never move nor change with respect to one another. They are arranged in a line parallel to the zodiac, and the middle one (Saturn itself) is about three times the size of the lateral ones [the edges of the rings]." He also described Saturn as having "ears". In 1612, the plane of the rings was oriented directly at the Earth and the rings appeared to vanish. Mystified, Galileo wondered, "has Saturn swallowed his children?", referencing the myth of Saturn's consumption of his children to prevent them from overthrowing him. They then reappeared in 1613, further confusing Galileo. Early astronomers used anagrams as a form of commitment scheme to lay claim to new discoveries before their results were ready for publication. Galileo used smaismrmilmepoetaleumibunenugttauiras for Altissimum planetam tergeminum observavi ("I have observed the most distant planet to have a triple form") for discovering the rings of Saturn.

In 1655, Christiaan Huygens became the first person to suggest that Saturn was surrounded by a ring. Using a 50 power refracting telescope that he designed himself, far superior to those available to Galileo, Huygens observed Saturn and wrote that "It [Saturn] is surrounded by a thin, flat, ring, nowhere touching, inclined to the ecliptic". Robert Hooke was another early observer of the rings of Saturn, and noted the casting of shadows on the rings.>>

[MarkBour]

Juno itself, might be the next significant Jovian impactor.

Given its mission length, it will not be the next impactor (unless something goes terribly wrong!) And given its mass, it will never be a significant impactor.

I certainly hope it is not.

From Wikipedia https://en.wikipedia.org/wiki/Juno_(spacecraft) the probe will be de-orbited to burn up in Jupiter's outer atmosphere, so as to avoid any possibility of impact and biological contamination of one of its moons.

This raises the concern of the contamination of Jupiter itself. I hope the entry does indeed sterilize everything, but just hearing of the plan leaves me with doubts about that.

[bystander]

Life On Titan Possible Without Water

Chemical Trail Could Lead to Clues About Life on Titan
Cornell University | 2016 July 06

Polymorphism and Electronic Structure of Polyimine and Its
Potential Significance for Prebiotic Chemistry on Titan - Martin Rahm et al

• Proceedings of the NAS (online 2016 May 20) DOI: 10.1073/pnas.1606634113

[Fred the Cat]

Study of the chemicals of the planets in our solar system may one day yield whether life developed on Earth itself or if precursors developed elsewhere then were later deposited on an Earth ready for later evolution. The rings and planets of Saturn seem like prime targets as does Jupiter if only because of their unique environments. It's a great time to be alive to see what Juno will find but I hope we will get to investigate the rings too.

I kind of favor that we find that life was "wisked' away from the rings.

[BMAONE23]

However, for a good view of Saturn's rings one really needs to be on a high inclination satellite like Siarnaq or Albiorix.

Thanks for the interesting data on these two moons. It appears that these little guys are not tidally locked. For the scenario I imagined to arise, one would have to have a large enough moon that people lived on one side of it and had never travelled to the planet-facing side until their society's mobility increased.

You bring up an interesting point that if they grew up on either Titan or Dione, then when they finally walked around, they'd not get a good view of the rings. But as you immediately pointed out as well, they would have the ring shadows for additional contemplation. I am finding this an equally fascinating question, actually, of how it would impact such a people to first view Saturn from a position that was precisely in the ring plane! They'd see a strange, thin, perfectly straight line bisecting the grand orb and extending beyond it. What religious debates would it induce? How much time would go by before some genius like Galileo explained that the shadows were shadows of the line? I think even people as sophisticated as our modern-day scientists would have had a hard time sorting that out and believing it, let alone humans from the year 1500.

I see a recent Cassini APOD that makes your point perfectly: http://apod.nasa.gov/apod/ap150824.html.

I guess I'm leaving out the other evidence that could have come their way by this point, if such a civilization developed similarly to ours. In the case of a moon of Jupiter or Saturn, if they had astronomers by that point, they would have been able to observe motions of many sister moons, and to wonder about them. Possibly they would even have put a fair number of their more intelligent folk to death by this point.

Part of the problem with any civilization developing on a moon is the probability of tidal locking and the effect of 100-200+ hour long days and nights
Ganymede's night lasts 86 hours.
Callisto's night lasts 204 hours
Europa's night lasts 42 hours
and Titan's night lasts 192 hours.

Too long in dark and too cold at their respective mean solar distances for surface dewllwers

[Chris Peterson]

Part of the problem with any civilization developing on a moon is the probability of tidal locking and the effect of 100-200+ hour long days and nights
Ganymede's night lasts 86 hours.
Callisto's night lasts 204 hours
Europa's night lasts 42 hours
and Titan's night lasts 192 hours.

Too long in dark and too cold at their respective mean solar distances for surface dewllwers

I think you're anthropomorphizing. Do not discount the power of evolution to mold life into its environment, even if that environment seems extreme to us.