APOD: Odysseus Crater on Tethys (2017 Feb 05)

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APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by APOD Robot » Sun Feb 05, 2017 5:40 am

Image Odysseus Crater on Tethys

Explanation: Some moons wouldn't survive the collision. Tethys, one of Saturn's larger moons at about 1000 kilometers in diameter, survived the collision, but today exhibits the resulting expansive impact crater Odysseus. Sometimes called the Great Basin, Odysseus occurs on the leading hemisphere of Tethys and shows its great age by the relative amount of smaller craters that occur inside its towering walls. The density of Tethys is similar to water-ice. The featured image was captured in November by the robotic Cassini spacecraft in orbit around Saturn as it swooped past the giant ice ball. Cassini has now started on its Grand Finale Tour which will take it inside Saturn's rings and culminate in September with a dive into Saturn's thick atmosphere.

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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by Boomer12k » Sun Feb 05, 2017 7:43 am

I wouldn't end a mission, until I had something to take its place... is there a Cassini II??
Because I am sure there is sooo much more to learn.

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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by Confused » Sun Feb 05, 2017 8:07 am

What collision?

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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by ta152h0 » Sun Feb 05, 2017 9:36 am

Ceres twin ?
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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by Ann » Sun Feb 05, 2017 9:53 am

Confused wrote:What collision?
The collision that led to the formation of the Odysseus impact basin on Tethys.
Saturn's moon Tethys with impact basin Odysseus.
NASA/JPL/Space Science Institute.
Image
Saturn's moon Mimas with crater Hershel.






















It is interesting to compare the two Saturnian moons, Tethys and Mimas, and their huge impact craters. Starting with the moons themselves, Tethys is larger than Mimas, with a mean radius of 531.1±0.6 km versus 198.2±0.4 km for Mimas. Mimas is also much less massive, 6.3×10−6 Earths (6.3 millionths of the mass of the Earth, I think) versus 1.03×10−4 Earths (one ten thousandth of the mass of the Earth) for Tethys. As you can tell from the image at left, Tethys is really far larger than Mimas.

The Odysseus impact basin is far wider than the Herschel crater, 400 kilometers versus 130 kilometers for Herschel. According to this page, Herschel covers 3% of the surface of Mimas, whereas Odysseus covers 4% of the surface of Tethys.

Clearly Odysseus is much shallower than Herschel, almost certainly because it is older. My extremely amateur guess is that the Odysseus impact could perhaps have melted more of the surface of Tethys and "flowed outwards" more than the impactor that created Herschel melted the surface of Mimas. But in any case: Yes, the impact on Tethys must have been larger than the impact on Mimas. But also, yes: both these moons must have been hit about as hard as they could be hit without shattering completely.

That was a solar system one-two punch heavyweight fight, that's for sure!

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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by De58te » Sun Feb 05, 2017 10:17 am

Boomer12k wrote:I wouldn't end a mission, until I had something to take its place... is there a Cassini II??
Because I am sure there is sooo much more to learn.

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Cassini is running out of rocket fuel. You might experience that when your car gas tank is empty. If they don't collide it soon then it would become un-manoeuverable and become a derelict which could threaten colliding with Enceladus, which possibly could have life in an underground ocean.
As far as I know there is no other probe planned for Saturn. There is Juno though at Jupiter and several around Mars.

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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by De58te » Sun Feb 05, 2017 10:39 am

Confused wrote:What collision?
Craters are believed to be created in three different ways. By volcano, either molten lava or cryogenic water. By explosions either nuclear or conventional. (this is rare for natural objects the size of moons.) Or, by collisions with wandering asteroids or comets. Since the word impact appears in impact crater, the impact is assumed to be caused by collisions.

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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by De58te » Sun Feb 05, 2017 11:02 am

ta152h0 wrote:Ceres twin ?
Not really, Ceres doesn't have a twin. Ceres, a former asteroid, now a Dwarf Planet is nearly twice as large as the next largest asteroid, Pallas.
If you are meaning size then Ceres would be the next smaller object in a list of objects in the inner Solar System. Ceres is 914 km in diameter, Tethys is 1,049 km diameter. On the other end, Dione would be closer in size at 1,120 km diameter, and it is also a moon of Saturn. (trivia, next in size would be Ariel, 1,158 km diameter, Umbriel, 1,168 km diameter, and Charon [Pluto] 1,189 km.)

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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by orin stepanek » Sun Feb 05, 2017 11:48 am

What a lovely rock collection Saturn has! :wink:
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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by heehaw » Sun Feb 05, 2017 3:33 pm

orin stepanek wrote:What a lovely rock collection Saturn has! :wink:
(I'd rather be a plutocrat, than be a plutopian, Orin!)

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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by neufer » Sun Feb 05, 2017 3:43 pm

Click to play embedded YouTube video.
orin stepanek wrote:
What a lovely rock collection Saturn has! :wink:
Look, Orin, I'm just not in the mood, O.K. ?
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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by orin stepanek » Sun Feb 05, 2017 5:28 pm

heehaw wrote:
orin stepanek wrote:What a lovely rock collection Saturn has! :wink:
(I'd rather be a plutocrat, than be a plutopian, Orin!)
Careful heehaw; Judy pinned that on me! :D
Orin

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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by Fred the Cat » Sun Feb 05, 2017 6:35 pm

Tethys's Odysseus Crater is definitely stage five. :wink:
Stage Five Planet.jpg
Like many of us. :(
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Re: APOD: Odysseus Crater on Tethys (2017 Feb 05)

Post by ta152h0 » Sun Feb 05, 2017 7:59 pm

reading through the thread I came to the conclusion you all are still funny as all get out .
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