APOD: Titan: Moon over Saturn (2018 May 26)

[APOD Robot]

Titan: Moon over Saturn

Explanation: Like Earth's moon, Saturn's largest moon Titan is locked in synchronous rotation. This mosiac of images recorded by the Cassini spacecraft in May of 2012 show's its anti-Saturn side, the side always facing away from the ringed gas giant. The only moon in the solar system with a dense atmosphere, Titan is the only solar system world besides Earth known to have standing bodies of liquid on its surface and an earthlike cycle of liquid rain and evaporation. Its high altitude layer of atmospheric haze is evident in the Cassini view of the 5,000 kilometer diameter moon over Saturn's rings and cloud tops. Near center is the dark dune-filled region known as Shangri-La. The Cassini-delivered Huygens probe rests below and left of center, after the most distant landing for a spacecraft from Earth.

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[scr33d]

It just so happened that yesterday I started to re-read Imperial Earth, by Clarke...

[heehaw]

After all these decades as an astronomer, first amateur then professional, I only became aware TODAY, from APOD, that Titan rotates synchronously!

[De58te]

After all these decades as an astronomer, first amateur then professional, I only became aware TODAY, from APOD, that Titan rotates synchronously!

That's probably because until Cassini's visit, nobody could tell if Titan was tidally locked because its dense atmosphere prevented anybody from seeing a surface feature. It was just presumed since all other major satellites are tidally locked to their primary.

[neufer]

After all these decades as an astronomer, first amateur then professional, I only became aware TODAY, from APOD, that Titan rotates synchronously!

That's probably because until Cassini's visit, nobody could tell if Titan was tidally locked because its dense atmosphere prevented anybody from seeing a surface feature. It was just presumed since all other major satellites are tidally locked to their primary.

Surface features on Titan were first identified in 1994 using infrared wavelengths on the newly refurbished Hubble Space Telescope.

25 moons are now known to be Synchronously tidally locked.

Only Saturn's Phoebe & Hyperion and Jupiter's Himalia & Elara are known not to be locked.

Code: Select all

           Radius    Mass                    Rotate  Dimensions
Name        (km)     (kg)   Dens  Abo    Vo  (days)     (km)
--------- -------  -------  ----  --- -----  ------  ----------
Moon         1738  7.35e22  3.34  .12 -12.7     S
.....................................................................
Phobos         11  1.08e16  1.9   .06  11.3     S    13.5 x 10.8 x 9.4
Deimos          6  1.80e15  1.8   .07  12.3     S    7.5 x 6.1 x 5.5
.....................................................................
Metis          20  9.56e16  2.8   .05  17.5     ?
Adrastea       10  1.91e16  4.5   .05  18.7     ?    12.5 x 10 x 7.5
Amalthea       94  3.5 e18  1.    .05  14.1     S    135 x 83 x 75
Thebe          50  7.77e17  1.5   .05  16.0     S    55 x 45
Io           1821  8.93e22  3.53  .61   5.0     S 
Europa       1565  4.80e22  2.99  .64   5.3     S
Ganymede     2634  1.48e23  1.94  .42   4.6     S
Callisto     2403  1.08e23  1.85  .20   5.6     S
Leda            8  5.68e15  2.7     ?  20.2     ?
Himalia        93  9.56e18  2.8     ?  15.0    0.4
Lysithea       18  7.77e16  3.1     ?  18.2     ?
Elara          38  7.77e17  3.3     ?  16.6    0.5
Ananke         15  3.82e16  2.7     ?  18.9     ?
Carme          20  9.56e16  2.8     ?  17.9     ?
Pasiphae       25  1.91e17  2.9     ?  16.9     ?
Sinope         18  7.77e16  3.1     ?  18.0     ?
.....................................................................
Pan            10     ?       ?   .5    ?       ? 
Atlas          15     ?       ?   .9   18.0     ?    20 x 10
Prometheus     46  2.70e17  0.7   .6   15.8     ?    72 x 43 x 32
Pandora        42  2.20e17  0.7   .9   16.5     ?    57 x 42 x 31
Epimetheus     57  5.59e17  0.6   .8   15.7     S    69 x 55 x 55
Janus          89  1.98e18  0.65  .8   14.5     S    99 x 96 x 76
Mimas         199  3.75e19  1.14  .5   12.9     S
Enceladus     249  7.30e19  1.12  .99  11.7     S
Tethys        530  6.22e20  1.00  .9   10.2     S
Telesto        15     ?       ?   .5   18.7     ?    17 x 14 x 13
Calypso        13     ?       ?   .6   19.0     ?    17 x 11 x 11
Dione         560  1.05e21  1.44  .7   10.4     S
Helene         16     ?       ?   .7   18.4     ?    18 x 16 x 15
Rhea          764  2.31e21  1.24  .7    9.7     S
Titan        2575  1.35e23  1.88  .21   8.3     S
Hyperion      143  1.77e19  1.4   .3   14.2  chaotic 185 x 140 x 113
Iapetus       718  1.59e21  1.02  .2   11.1     S    (y)
Phoebe        110           1.6   .06  16.5    0.4   115 x 110 x 105
.....................................................................
Cordelia       13     ?       ?   .07  24.0     ?
Ophelia        16     ?       ?   .07  24.0     ?
Bianca         22     ?       ?   .07  23.0     ?
Cressida       33     ?       ?   .07  22.0     ?
Desdemona      29     ?       ?   .07  22.0     ?
Juliet         42     ?       ?   .07  22.0     ?
Portia         55     ?       ?   .07  21.0     ?
Rosalind       27     ?       ?   .07  22.0     ?
Belinda        34     ?       ?   .07  22.0     ?
Puck           77     ?       ?   .07  20.0     ?
Miranda       236  6.59e19  1.20  .27  16.5     S    240 x 234 x 233
Ariel         581  1.35e21  1.67  .34  14.4     S    581 x 578 x 578
Umbriel       585  1.17e21  1.40  .18  15.3     S
Titania       789  3.53e21  1.71  .27  14.0     S
Oberon        761  3.01e21  1.63  .24  14.2     S
Caliban        40                 .07  21.9
Stephano       15                 .07  24.3
Sycorax        80                 .07  20.4
Prospero       20                 .07  23.2
Setebos        20                 .07  23.3
.....................................................................
Naiad          29     ?       ?   .06  25.0     ?
Thalassa       40     ?       ?   .06  24.0     ?
Despina        74     ?       ?   .06  23.0     ?
Galatea        79     ?       ?   .06  23.0     ?
Larissa        96     ?       ?   .06  21.0     ?    104 x 89
Proteus       209     ?       ?   .06  20.0     ?    218 x 208 x 201
Triton       1353  2.15e22  2.05  .7   13.6     S
Nereid        170     ?       ?   .2   18.7     ?
.....................................................................
Charon        603  1.52e21  1.72  .32  15.5     S    (z)
Nix            23   < 2e18    ?     ?  22.9     ?    (z)
Hydra          30   < 2e18    ?     ?  23.4     ?    (z)
----------------------------------------------------------------

[Rusty Brown in Cda]

"...show's its anti-Saturn side..."
They're putting apostrophes in verbs now?

[Steve Dutch]

Note how you can see a zone where the rings are visible but distorted by Titan's upper atmosphere.

Cassini was the most awesomely perfect mission ever flown.

[ta152h0]

I don't remember ever seeing this before. Keep posting images never seen before, like F4 Phantoms chasing Gemini 2 launches.

[ta152h0]

You are all supercalifragicetc !

[heehaw]

A couple of moons, as I recall, are chaotic in their rotation! What if our own Moon had been chaotic in its rotation! Whee!

[Beechy]

Is the visible line, the high altitude haze that's mentioned? Why is it visible?

[saturno2]

Titan is a Moon very interesting because
it has atmosphere and liquids on the surface

[neufer]

Is the visible line, the high altitude haze that's mentioned? Why is it visible?

• [Sense of "confusion, vagueness."]
  
  Because that's what defines a haze
  
  https://apod.nasa.gov/apod/ap160609.html

haze (n.) "opaqueness of the atmosphere," 1706, probably a back-formation of hazy (q.v.). Sense of "confusion, vagueness" is 1797. The differentiation of haze, mist, fog (and other dialectal words) is unmatched in other tongues, where the same word generally covers all three and often "cloud" as well; this may be an effect of the English climate on the English language.

hazy (adj.) 1620s, hawsey, nautical, of unknown origin. Some connect it with German hase "hare," an animal which plays an important part in Germanic folklore, with many supernatural and unlucky aspects in medieval times (among the superstitions: a dead hare should not be brought aboard a fishing ship, and the word hare should not be spoken at sea). Another suggestion is Old English hasu, haswe "gray."