So, How big are the tides on Titan?

Just wondering how big the tides on Titan might be?

Maybe they're huge?

Low gravity in conjunction with a really big moon called Saturn. After all
motion is relative. ;-)

Craig Fink

On 2005-01-17, Craig Fink wrote:
Just wondering how big the tides on Titan might be?

Maybe they're huge?

Low gravity in conjunction with a really big moon called Saturn. After all
motion is relative. ;-)

I spent Friday watching the ESA TV feed, which included an interview
with someone who'd been working on what to do if Huygens ended up in the
"water". He commented that they'd modelled the hypothetical oceans, by
taking something intended to model oceanic behaviour and changing
virtually every parameter in it, and that the eventual result was that
they expected to get waves which were much larger, but also much slower,
than on Earth; I think a figure quoted was about five? times the height,
but spaced significantly further apart.

Not quite tides, but...

--
-Andrew Gray

In article ,
Craig Fink wrote:
Just wondering how big the tides on Titan might be?
Maybe they're huge?

Yes and no. Your intuition is correct that Saturn will raise very large
tidal bulges in Titan. *However*, Titan is tide-locked to Saturn, so
those big bulges don't move around much -- the moon is basically just a
little bit egg-shaped all the time.

Titan's slightly elliptical orbit will cause the bulges to move around a
little, and also to change height slightly as the distance from Saturn
changes. So they aren't *quite* completely fixed, but fairly close to it.

(This *was* used to put some constraints on the possibility of a global
ocean on Titan: tidal dissipation effects would have circularized Titan's
orbit long ago if it had a shallow global ocean, especially one obstructed
by islands and continents like Earth's. Titanian oceans had to be either
fairly deep and essentially land-free, or broken up into multiple
unconnected regional oceans.)
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

On Tue, 18 Jan 2005 05:15:00 +0000, Henry Spencer wrote:

In article , Craig Fink
wrote:
Just wondering how big the tides on Titan might be? Maybe they're huge?

Yes and no. Your intuition is correct that Saturn will raise very large
tidal bulges in Titan. *However*, Titan is tide-locked to Saturn, so
those big bulges don't move around much -- the moon is basically just a
little bit egg-shaped all the time.

Titan's slightly elliptical orbit will cause the bulges to move around a
little, and also to change height slightly as the distance from Saturn
changes. So they aren't *quite* completely fixed, but fairly close to
it.

(This *was* used to put some constraints on the possibility of a global
ocean on Titan: tidal dissipation effects would have circularized
Titan's orbit long ago if it had a shallow global ocean, especially one
obstructed by islands and continents like Earth's. Titan oceans had to
be either fairly deep and essentially land-free, or broken up into
multiple unconnected regional oceans.)


Yes, but it's not always tide-locked. Anytime that there is a significant
impact, one that might cause a large crater, it changes the velocity of
Titan's orbit (changing it's orbital period) and changes Titan's angular
momentum (rotation rate). Now the tidal bulge is going to start moving
very slowly round and round Titan until all the energy is used up and it
becomes tide-locked again. Then the next impact, and the next.

If the tidal bulge is really large, it could be like an "ocean tide" where
the entire ocean goes round and round the moon very slowly. A new form of
erosion, with "tidal rivers".

Still wondering exactly how big Titan's tidal bulge is?

Craig Fink

Henry Spencer wrote:
In article ,
Craig Fink wrote:

Just wondering how big the tides on Titan might be?
Maybe they're huge?


Yes and no. Your intuition is correct that Saturn will raise very large
tidal bulges in Titan. *However*, Titan is tide-locked to Saturn, so
those big bulges don't move around much -- the moon is basically just a
little bit egg-shaped all the time.

Titan's slightly elliptical orbit will cause the bulges to move around a
little, and also to change height slightly as the distance from Saturn
changes. So they aren't *quite* completely fixed, but fairly close to it.


How about tides due to other moons? (I think Rhea or Dione would be the
best candidates.) They wouldn't be anything like the size of our lunar
tides, but maybe there'd be a measurable effect.

--

Fin

)

In article ,
Fin Fahey wrote:
Yes and no. Your intuition is correct that Saturn will raise very large
tidal bulges in Titan. *However*, Titan is tide-locked to Saturn, so
those big bulges don't move around much...

How about tides due to other moons? (I think Rhea or Dione would be the
best candidates.) They wouldn't be anything like the size of our lunar
tides, but maybe there'd be a measurable effect.

Alas, I fear not. The Saturnian system is a big place. The distance
between Titan and Rhea is never *less* than about twice the distance from
the Earth to the Moon. I haven't time right now to wade through the
numerical details, but it looks to me like inter-moon tides are going to
be quite insignificant.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

JRS: In article , dated Wed, 19 Jan 2005
15:20:10, seen in news:sci.space.policy, Henry Spencer
posted :

The distance
between Titan and Rhea is never *less* than about twice the distance from
the Earth to the Moon.

Contributory, but non-essential.

I haven't time right now to wade through the
numerical details, but it looks to me like inter-moon tides are going to
be quite insignificant.

Assuming no Saturnian moon is much denser than say 3 (if it was 10 or
more I'd remember) :

At closest to Titan, in Moore units,
Saturn subtends 75100/760000 radians, say 0.1
Rhea subtends 1100/432000, say 0.0025
Hyperion subtends 200/160000, say 0.00125
Iapetus subtends 2000?/1440000, say 0.0015
and the rest are obviously smaller.

Tidal force goes as cube of angular diameter times density; so Rhea's
tide at Titan is of the order of 50 ppm of Saturn's.

At closest to Hyperion, i M u,
Saturn subtends 75100/920000 radians, say 0.08
Titan subtends 3500/160000, say 0.02

So the tidal force of Titan at Hyperion is about 5% of Jupiter's.

--
© John Stockton, Surrey, UK. Turnpike v4.00 MIME. ©
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
some Astro stuff via astro.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

Dr John Stockton wrote:

JRS: In article , dated Wed, 19 Jan 2005
15:20:10, seen in news:sci.space.policy, Henry Spencer
posted :

The distance
between Titan and Rhea is never *less* than about twice the distance
from the Earth to the Moon.

Contributory, but non-essential.

The effect of tides is proportional to:

m1.r2^4/m2.d^3

where m1 = mass of inducing body
m2 = mass of subject body
r2 = radius of subject body
d = distance between the bodies

Plugging in the numbers for an assortment of solar system bodies, we get
the table below. (Tidal effects are normalised to Moon-on-Earth = 1.
When both bodies are moons of the same planet, the minimum distance is
used.)

Inducing Subject m1 m2 r2 d Tidal
body body (kg) (kg) (m) (m) effect
-------- -------- -------- -------- ------- -------- -------
Sun Earth 1.989e30 5.974e24 6.378e6 1.496e11 0.459
Moon Earth 7.349e22 5.974e24 6.378e6 3.844e8 1
Sun Moon 1.989e30 7.349e22 1.738e6 1.496e11 0.206
Earth Moon 5.974e24 7.349e22 1.738e6 3.844e8 36.4
Sun Mercury 1.989e30 3.302e23 2.440e6 5.791e10 3.07
Sun Venus 1.989e30 4.869e24 6.052e6 1.082e11 1.21
Sun Mars 1.989e30 6.419e23 3.397e6 2.279e11 0.0973
Sun Io 1.989e30 8.932e22 1.822e6 7.784e11 0.00145
Jupiter Io 1.899e27 8.932e22 1.822e6 4.216e8 8720
Europa Io 4.800e22 8.932e22 1.822e6 2.493e8 1.07
Ganymede Io 1.482e23 8.932e22 1.822e6 6.484e8 0.187
Callisto Io 1.076e23 8.932e22 1.822e6 1.461e9 0.0119
Sun Europa 1.989e30 4.800e22 1.561e6 7.784e11 0.00146
Jupiter Europa 1.899e27 4.800e22 1.561e6 6.709e8 2170
Io Europa 8.932e22 4.800e22 1.561e6 2.493e8 1.99
Ganymede Europa 1.482e23 4.800e22 1.561e6 3.991e8 0.805
Callisto Europa 1.076e23 4.800e22 1.561e6 1.212e9 0.0209
Sun Ganymede 1.989e30 1.482e23 2.631e6 7.784e11 0.00380
Jupiter Ganymede 1.899e27 1.482e23 2.631e6 1.070e9 1400
Io Ganymede 8.932e22 1.482e23 2.631e6 6.484e8 0.296
Europa Ganymede 4.800e22 1.482e23 2.631e6 3.991e8 0.681
Callisto Ganymede 1.076e23 1.482e23 2.631e6 8.130e8 0.181
Sun Callisto 1.989e30 1.076e23 2.410e6 7.784e11 0.00369
Jupiter Callisto 1.899e27 1.076e23 2.410e6 1.883e9 249
Io Callisto 8.932e22 1.076e23 2.410e6 1.461e9 0.0251
Europa Callisto 4.800e22 1.076e23 2.410e6 1.212e9 0.0236
Ganymede Callisto 1.482e23 1.076e23 2.410e6 8.130e8 0.241
Sun Titan 1.989e30 1.346e23 2.575e6 1.427e12 6.24e-4
Saturn Titan 5.685e26 1.346e23 2.575e6 1.222e9 284
Tethys Titan 6.27e20 1.346e23 2.575e6 9.273e8 7.17e-4
Dione Titan 1.10e21 1.346e23 2.575e6 8.446e8 0.00166
Rhea Titan 2.31e21 1.346e23 2.575e6 6.950e8 0.00627
Hyperion Titan 2e19 1.346e23 2.575e6 2.590e8 0.00105
Iapetus Titan 1.59e21 1.346e23 2.575e6 2.339e9 1.13e-4
Sun Triton 1.989e30 2.14e22 1.353e6 4.498e12 9.55e-6
Neptune Triton 1.024e26 2.14e22 1.353e6 3.548e8 1000
Proteus Triton 5e19 2.14e22 1.353e6 2.372e8 0.00164
Nereid Triton 3e19 2.14e22 1.353e6 5.158e9 9.55e-8
Sun Pluto 1.989e30 1.25e22 1.195e6 5.906e12 4.40e-6
Charon Pluto 1.62e21 1.25e22 1.195e6 1.960e8 0.0979
Sun Charon 1.989e30 1.62e21 5.93e5 5.906e12 2.06e-6
Pluto Charon 1.25e22 1.62e21 5.93e5 1.960e8 0.354

--
Ross Smith ......... ......... Auckland, New Zealand
"If you can keep your head when all about you are losing theirs,
then you probably haven't checked with your answering service."
-- Capt. B. F. Pierce

Dr John Stockton wrote:

Tidal force goes as cube of angular diameter times density

Sure sounds right. Thanks for that.

I think most flexing of tide locked moons comes from eccentric orbits
(higher tides at periapsis, lower at apoapsis)


There is another source of flexing I've been wondering about.

My image of a tidelocked moon is a watermelon being spun about Saturn:

http://clowder.net/hop/tidemoon.jpg

Under normal circumstances the long axis of the watermelon remains
pointed toward Saturn.

But a brush against the watermelon would cause its long axis to wobble
some. I imagine it would be like a pendulum.

If another moon's synodic period were resonant with the period of this
"pendulum", the wobble could build with time.



--
Hop David
http://clowder.net/hop/index.html

(Henry Spencer) writes:

Alas, I fear not. The Saturnian system is a big place. The distance
between Titan and Rhea is never *less* than about twice the distance from
the Earth to the Moon.

Wow, that puts things into perspective in a really solid manner.

I had a mental image of things being much smaller. So then just going from
moon to moon is a non-trivial task, even after having sufficient technology to
get there in the first place.

-gc

--
Old aunts used to come up to me at weddings, poking me in the ribs and
cackling, telling me, "You're next." They stopped after I started doing the
same thing to them at funerals.