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Fraser
2004-Oct-21, 04:22 PM
SUMMARY: One of the six scientific instruments on board the European Space Agency's Huygens probe is a tiny microphone designed to help scientists listen for lightning strikes as the spacecraft descends through the atmosphere of Saturn's moon, Titan. Huygens is scheduled to arrive at Titan on January 14, 2005, after it's released by NASA's Cassini spacecraft. If Huygens actually passes through a storm, the microphone should actually be able to pick up the sound of liquid methane rain splashing against the spacecraft's casing. If the probe does find thunderstorms, this could indicate that they're part of the process that helps create the organic molecules detected in the moon's atmosphere.

What do you think about this story? Post your comments below.

lswinford
2004-Oct-21, 06:51 PM
Trying to picture the cold, dense environment, I bet the sounds will more resemble those to be heard in a deep-diving whale's gut than a light prarie thunderstorm I might hear in springtime. I sure hope it works, but I'm certain it will sound really strange.

antoniseb
2004-Oct-21, 08:10 PM
Originally posted by lswinford@Oct 21 2004, 06:51 PM
I'm certain it will sound really strange.
It might sound strange. In any case, we only have to wait another three months.

TuTone
2004-Oct-21, 08:29 PM
Can't wait for this mission! I hope everything goes well.

Guest
2004-Oct-21, 09:28 PM
Why do we expect thunderstorms on Titan? I thought Titan was one frozen methane lake or whatever the stuff at the surface turns out to be, very very cold. How do thunderstorms work on such a world? Anyone know details?

Cheers.

Janice
2004-Oct-22, 01:32 AM
:D THIS IS SO EXCITING!!!!!!! :D

SupaGlu
2004-Oct-22, 08:32 AM
Anwhere where there is a dense atmosphere there are likely to be thunderstorms due to friction, are currents and temperature variations.

VanderL
2004-Oct-23, 10:53 AM
Hi SupaGlu,

It takes a heat source to get thunderstorms, where is the heat coming from? Surely not the tiny speck in Titan's sky known as the Sun, the dense atmosphere will not even let this light pass properly or we would be able to see Titan's surface without radar.

Cheers.

Duane
2004-Oct-23, 11:16 PM
It takes a heat source to get thunderstorms,

Um, why do you think they are thunderstorms VanderL? I have seen nothing to suggest anyone sees or expects thunderstorms on Titan.

Lightning does not require a heat source. The build up of charge can occur in something as simple as rubbing your feet across a carpet.

VanderL
2004-Oct-23, 11:28 PM
Umm..


If the probe does find thunderstorms, this could indicate that they're part of the process that helps create the organic molecules detected in the moon's atmosphere.


This is a quote from the article summary, maybe I didn't read it correctly? ;)

Cheers.

Duane
2004-Oct-24, 08:32 PM
Hrmm, maybe I didn't :)

The journalist who wrote the article probably got the thunderstorm idea from the Hyugens science team's description of the experiment--although, perhaps thunderstorm is an apt phrase. Not totally accurate in the case of Titan, but apt.

Thunderstorms on Earth, Saturn and Jupiter are associated with water-clouds forming in the atmosphere. I don't think water clouds can form on Titan, so I'm not sure that you could call them "storms" per say.

Course, I have been wrong before..............

VanderL
2004-Oct-24, 10:38 PM
Hi Duane,

You wrong? Naah. :D

Ok, so whatever we call the storms, how is lightning generated on Titan in your view? Or are they only after rainstorms?

Cheers.

GOURDHEAD
2004-Oct-24, 11:42 PM
It takes a heat source to get thunderstorms, where is the heat coming from?

Indeed it takes a generator of kinetic energy (wind, air in motion) to produce thunderstorms. My guess is that there is enough pressure differential across Titan to cause the wind to blow, create the friction that causes the ionization that sustains the electrical energy that supports the thunderstorms. The answer must lie in the variation in temperature from Titan's mean temperature from place to place giving rise to flows of atmospheric cells.

VanderL
2004-Oct-25, 01:39 PM
Hi Gourdhead,

I agree with your description of the possible cause, but where is the energy coming from?
If we exclude the influence of sunlight as a possible energy source for creating the atmospheric cells (I think the Sun can't contribute enough at that distance), do we need to theorize on an internal heatsource, just like on Io, Triton and all the the gas giants?

Cheers.

Duane
2004-Oct-25, 06:05 PM
If we exclude the influence of sunlight as a possible energy source for creating the atmospheric cells

VanderL you can't exclude the energy from the sun in making such a calculation. Although the energy arriving at Titan is significantly less than that arriving at Earth, there is still energy arriving. Considering that the mean temperature of Titan is so low, it doesn't take alot of extra energy to precipitate atmospheric cell formation. Even without geothermal energy, the net energy arriving from the sun would be enough to trigger pressure differences in Tital's atmosphere--and that is all that is needed for "weather".

Now, if there is also geothermal activity, then the net effect could be substancial.

I also think Gourdhead's explanation is absolutely correct--it is the movement of the airmass and the resulting friction that charges the atmoshere enough to create lightning discharges. And no, it is not required that water be involved for lightning to be present. It is also not necessary for there to be any other outside sources of energy to initiate the cell formation in the Titan atmosphere.

VanderL
2004-Oct-25, 07:03 PM
Hi Duane,

Stay cool, thanks for answering the question.
Are there any calculations that show it really is possible to get lightning on Titan, how little energy is required for this to happen?
It's not just the amount of energy arriving at Titan, it is also the amount of energy reaching the surface, remember Titan's atmosphere is extremely opaque, more so than Earth's. I've searched for information but I still don't know where this idea that Titan has thunderstorms comes from, are there maybe any indications from the earlier missions?

Cheers.

Duane
2004-Oct-25, 07:18 PM
Are there any calculations that show it really is possible to get lightning on Titan, how little energy is required for this to happen?


No idea. I would think that the kenetic energy arising from the interaction of the coulds/atmosphere of Titan would be enough to invoke lightning, but I am only guessing.


It's not just the amount of energy arriving at Titan, it is also the amount of energy reaching the surface,

Well, no actually. It is the differencial warming that will produce convection cells, even if that warming only takes place in the upper areas of the atmosphere. You don't need surface warming, although that would add to the mix, if it could happen.


where this idea that Titan has thunderstorms comes from, are there maybe any indications from the earlier missions?


Me either, although I suspect it's anticipated because of the thickness of the atmosphere combined with hints of cloud movement. Basically, if the atmosphere has convection cells, friction between the air masses should be enough to produce electricity--lightning.

Spacemad
2004-Oct-25, 10:00 PM
Couldnīt the gravity effect of Saturn itself be capable of causing some heating in Titan due to tidal effects? I believe that is one of the ideas for the volcanic activity of Io (yes, I know itīs a lot closer to Jupiter than Titan is to Saturn). :unsure:

VanderL
2004-Oct-25, 10:54 PM
Hi Spacemad,

I'm not sure but isn't Titan tidally locked always facing Saturn the same way?

Cheers.

Duane
2004-Oct-25, 11:38 PM
Titan is tidally locked. Titan is not close enough to other bodies in the Saturin system to experience much in the way of tidal heating, such as is seen on Io.

Titan is almost as big as Ganymede, and bigger than either Mercury or Pluto. It is unlikely to have much in the way of geologic activity, at least in the form of tectonics.

Spacemad
2004-Oct-26, 07:45 AM
Thanks, Duane, for clearing up that point. I had no idea that Titan was tidally locked to Saturn. Like our Moon Titan turns on its axis in the same time it takes to complete an orbit around Saturn.

GOURDHEAD
2004-Oct-26, 01:57 PM
I agree with your description of the possible cause, but where is the energy coming from?


Titan is tidally locked. Titan is not close enough to other bodies in the Saturin system to experience much in the way of tidal heating, such as is seen on Io.

Even though tidally locked to Saturn as pointed out, the distance of Titan from Saturn will change as Titan traverses its orbit from "aposaturn" to "perisaturn" and is irridated by particles accelerated by Saturn's magnetic field. I'm not familiar with the eccentricity of Titan's orbit (approximately 0.03) but the gravitational flexing from this effect could provide some heat as will the intercepting of the particles accelerated in Saturn's magnetic field. Also the insulation properties of Titan's atmosphere may allow it to keep a larger fraction of its heat than objects with different or less atmosphere. Although at a lesser ratio than on earth, Titan must have radioactive isotopes near its core from the same source as those in earth and these will provide some heating as does direct radiation from the sun.

At 10 AU Titan recieves 0.01 as much radiation as earth which receives 1300 watts per square meter. Thirteen watts per square meter over pi times 2575^2 meters (270,662,112.5 joules per second) may provide enough heat to generate some lightning especially if the combined radiation and reflection from Titan is less than 13 watts per square meter

I seem to remember a report of the observation of cloud movement on Titan within the last several years. If clouds move, lightning is likely to happen.