APOD: Jupiters Rings Revealed (2012 Jun 17)

[APOD Robot]

Jupiters Rings Revealed

Explanation: Why does Jupiter have rings? Jupiter's rings were discovered in 1979 by the passing Voyager 1 spacecraft, but their origin was a mystery. Data from the Galileo spacecraft that orbited Jupiter from 1995 to 2003 later confirmed that these rings were created by meteoroid impacts on small nearby moons. As a small meteoroid strikes tiny Adrastea, for example, it will bore into the moon, vaporize, and explode dirt and dust off into a Jovian orbit. Pictured above is an eclipse of the Sun by Jupiter, as viewed from Galileo. Small dust particles high in Jupiter's atmosphere, as well as the dust particles that compose the rings, can be seen by reflected sunlight.

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[Ann]

Nice reminder. Yes, all the big planets in our solar system - Jupiter, Saturn, Uranus and Neptune - have rings.

The question is why the rings of Saturn are so different from the rings of the other planets. Perhaps the rings of Saturn were created when a moon was torn apart by tidal forces, while the other rings were made by tiny impacts on moons of the planets.

Two (or three) of the moons of Saturn are also most remarkable: Titan, Enceladus and Iapetus. It has been hypothesized that the thick atmosphere of Titan may have been made when frozen nitrogen on the surface of Titan was made to sublimate. I can't help wondering if the creation of the rings of Saturn has anything at all to do with the thick atmosphere on Titan, the tectonic activity on Enceladus and the strange appearance of Iapetus.

But that is pure speculation on my part.

Ann

[Donn]

But that is pure speculation on my part.

Ann

Which is always appreciated!

My comment is, if I were in a position to have a new start up company, this picture is the logo I would choose.

[UWe]

Could the shady structure at the bottom of the left fringe be interpreted as the GRS?

[neufer]

Could the shady structure at the bottom of the left fringe be interpreted as the GRS?

• The Great Red Spot (GRS) is just 22° south of Jupiter's equator;
  the shady structure is at least 33° south of Jupiter's equator.

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<<The South Temperate Region, or South Temperate Belt (STB), is yet another dark, prominent belt, more so than the NTB; until March 2000, its most famous features were the long-lived white ovals BC, DE, and FA, which have since merged to form Oval BA ("Red Jr."). The ovals actually were part of South Temperate Zone, but they extended into STB partially blocking it.The STB has occasionally faded, apparently due to complex interactions between the white ovals and the GRS. The appearance of the South Temperate Zone (STZ)—the zone in which the white ovals originated—is highly variable.>>

[UWe]

Thanks a lot, it''s clearly distinguishable by comparing the two images.

[BoulderBoy]

I like these pictures of the planets silhouetted by the sun, but I have never seen, nor can I find by searching, such a picture of the Earth. Do you have a picture of the Earth silhouetted by the Sun? Does such a picture also reveal a ring of debris, possibly largely man made? Just curious.

[George]

"Jupiter's rings were discovered in 1979 by the passing Voyager 1 spacecraft ..."

Actually, confirmed would be more accurate. Evidence for a Jupiter ring in the form of an equatorial shadow line was discovered by amateur astronomers long before Voyager.

George

[neufer]

I like these pictures of the planets silhouetted by the sun, but I have never seen, nor can I find by searching, such a picture of the Earth. Do you have a picture of the Earth silhouetted by the Sun? Does such a picture also reveal a ring of debris, possibly largely man made? Just curious.

We have met the debris and they is us:

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A Technological Civilization by Night
by Paul Gilster on November 16, 2007

Rosetta makes its reappearance at just the right time for me. The spacecraft, making its second Earth swing-by on November 13, will use its gravity assists past Earth and Mars to reach Comet 67P/Churyumov-Gerasimenko in 2014, deploying a lander onto the nucleus and spending two years orbiting the comet. The close approach produced the memorable image. Look at those city lights!

Rosetta view of Earth: This is a composite of four images combined to show the illuminated crescent of Earth and the cities of the northern hemisphere. The images were acquired with the OSIRIS Wide Angle Camera during Rosetta’s second Earth swing-by on Nov. 13. This image showing islands of light created by human habitation was taken with the OSIRIS WAC at 19:45 CET, about 2 hours before the closest approach of the spacecraft to Earth. At the time, Rosetta was about 80,000 km above the Indian Ocean where the local time approached midnight (the angle between Sun, Earth and Rosetta was about 160°). The image was taken with a five-second exposure of the WAC with the red filter. This image showing Earth’s illuminated crescent was taken with the WAC at 20:05 CET as Rosetta was about 75,000 km from Earth. The crescent seen is around Antarctica. The image is a color composite combining images obtained at various wavelengths. Credit: ESA ©2005 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA.>>

[Ann]

Space debris around the Earth. Credit: ESA

Neufer wrote:

We have met the debris and they is us:

http://orbiterchspacenews.
blogspot.se/2010/11/
russia-to-lean-space-around-earth.html wrote:

Every year, the space near Earth becomes more and more densely populated with used satellites and their debris

Ann

[neufer]

Two (or three) of the moons of Saturn are also most remarkable: Titan, Enceladus and Iapetus. It has been hypothesized that the thick atmosphere of Titan may have been made when frozen nitrogen on the surface of Titan was made to sublimate. I can't help wondering if the creation of the rings of Saturn has anything at all to do with the thick atmosphere on Titan, the tectonic activity on Enceladus and the strange appearance of Iapetus.

[b][color=#0000FF][size=150]Crescent Titan with a cloud cap?[/size][/color][/b]

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Pretty picture: Halo on a halo?
Posted By Emily Lakdawalla
2012/06/15 05:21 CDT

<<Cassini took this photo of Titan on June 6, 2012, on its way into the "T83" flyby. Cassini sees Titan at very high phase, and the Sun lights up its atmosphere from behind.

This image is cool to begin with because it's taken at such a high phase that we can see sunlight scattering through Titan's atmosphere completely around its globe. You're seeing every sunrise and sunset happening all over Titan, all at once. What makes it curious is the little lenticular cap at the bottom of the image, at Titan's southern winter pole. The cap is also visible in images of Titan taken as Cassini was departing the flyby, like this one. If something like this has been visible in Cassini's images of Titan before, I don't recall seeing it. (Please point it out in the comments if it's been seen before.) I don't have any idea what it is. Hopefully someone will tell me in a talk at the Division of Planetary Sciences meeting in the fall. Cassini has been at Saturn for very nearly eight years, and has flown past Titan a hundred times, and there are still new things to see!

[Kerry]

Why doesn't the top part of the ring on the left side - not in Jupiters shadow - meet Jupiter as it does on the right side?

[Uwe]

Why doesn't the top part of the ring on the left side - not in Jupiters shadow - meet Jupiter as it does on the right side?

I think that's because this image is a mosaic. Probably some data is simply missing.
Check the Link under "Pictured above" (http://photojournal.jpl.nasa.gov/catalog/pia01621) for more details.

[neufer]

Why doesn't the top part of the ring on the left side - not in Jupiters shadow - meet Jupiter as it does on the right side?

I think that's because this image is a mosaic. Probably some data is simply missing.
Check the Link under "Pictured above" (http://photojournal.jpl.nasa.gov/catalog/pia01621) for more details.

<<The resolution is approximately 46 kilometers per picture element from right to left; however,
because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction.>>

My guess is that the spacecraft was indeed about 0.5 degrees above the ring plane in the right hand shot;
however, it was probably about 0.5 degrees below the ring plane in the left hand shot.

The left hand side of the planet doesn't show the ring at all
because the spacecraft was passing through the ring plane at that time.

The sun is always above the ring plane such that the left hand shot had to be carefully enhanced to make it appear to be compatible with the right hand shot; this wasn't a problem since this shot didn't include any of the planet itself. However, the resulting illusion that one is seeing a seamless view of the upper ring plane is broken by the (left/middle) shot that doesn't pick up the ring plane at all.

[flash]

So all the big planets in our solar system - Jupiter, Saturn, Uranus and Neptune - have rings. I wonder: Are all the rings equatorial? They certainly seem so from all the images I've seen of the rings of Saturn and the banding of the clouds... Further, all the rings seem to be in the same plane. I suppose that if all the satellites are orbiting in the same plane then the rings they create / shepherd would be in that same plane, but why equatorial? Is there evidence of a ring system in a more polar orbit somewhere? If not, why? If two rings were somehow created NOT in the same plane, how would they evolve? (Either intersecting or not...)

My mind wanders from rings back to spiral galaxies and their angular momentum... Well-formed spiral galaxies seem mostly planar (at least they are the farther from the galactic center you go). Although the scales are vastly different, could not the mechanism that causes spiral galaxies to be planar also be the same (or similar) mechansim that causes rings to be planar?

If a star orbiting a galaxy is somehow perturbed out of the plane of the galaxy, is there not some restorative force (presumably from the vast mass of the other stars still in the plane) that causes it to rejoin them eventually? Is it not so also for a bit of ring debris?

[Chris Peterson]

So all the big planets in our solar system - Jupiter, Saturn, Uranus and Neptune - have rings. I wonder: Are all the rings equatorial? They certainly seem so from all the images I've seen of the rings of Saturn and the banding of the clouds... Further, all the rings seem to be in the same plane. I suppose that if all the satellites are orbiting in the same plane then the rings they create / shepherd would be in that same plane, but why equatorial? Is there evidence of a ring system in a more polar orbit somewhere? If not, why? If two rings were somehow created NOT in the same plane, how would they evolve?

Ring systems almost have to be equatorial, because the large gas planets they surround are significantly oblate. That means that an equatorial orbit is the only one that can be circular (a requirement for ring systems), and it means that tidal forces will actively keep the particles on the equatorial plane.

My mind wanders from rings back to spiral galaxies and their angular momentum... Well-formed spiral galaxies seem mostly planar (at least they are the farther from the galactic center you go). Although the scales are vastly different, could not the mechanism that causes spiral galaxies to be planar also be the same (or similar) mechansim that causes rings to be planar?

The vast majority of the mass of a spiral galaxy is not orbiting on any particular plane. The disc material that is presumably got that way because of non-gravitational forces that existed early in their formation process... the same reason that most of the bodies in the Solar System are roughly coplanar. In the case of galaxies, and of our Solar System, there are few if any forces acting today that keep things planar, which is not the case for ring systems.

If a star orbiting a galaxy is somehow perturbed out of the plane of the galaxy, is there not some restorative force (presumably from the vast mass of the other stars still in the plane) that causes it to rejoin them eventually? Is it not so also for a bit of ring debris?

There are no forces acting to keep or force stars into planar galactic orbits. Most of the stars in typical galaxies are in the bulge, where they are orbiting at random inclinations. As noted, tidal forces maintain planetary rings in equatorial orbits.