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[10ebbor10]

The Icecube project works by detecting the very tiny flashes of light that are made when a neutrino collides with the ice.

The clearity of  the ice allows them to scan 1km³ of ice with only a limited amount of sensors, and detect even the tiniest flashes.

[Lagslayer]

Is Space Cthulhu better or worse than regular Cthulhu?

[10ebbor10]

Depends. Space Cuthulu generally limits himself to rockets, but is deadly.

[kaian-a-coel]

Many kerbals have fallen to his deadly tentacled glitches.

[Scoops Novel]

This whole endeavour needs to be done properly. I.e., it has to impress the local life forms.

This means that it has to have the most bang factor possible.

The old Orion project will be resuscitated, essentially sending the spaceship riding on top of a string of nuclear explosions.
Once there, a probe will descend onto the suface, and use a plutonium pellet-tipped drill to melt through the ice.
When that's done, it will send a kiloton-sized nuclear explosion device to the bottom of the ocean, and use its sensitive equipment to find out if there are any life forms moving about to help the survivors.
If it doesn't detect any, it'll activate it's 50-megaton self-destruct mechanism, allowing the scientists on Earth to detect the radiation signature coming from beneath the ice.
If it does detect life, it'll activate both of its self-destruct mechanisms, allowing the scientists to detect a differing signature.
Should it fail to detonate any of these, it'll surely mean that the local life forms have the technology to disable nuclear devices, and are probably pissed off now. So a fail-safe mechanism will activate in the spaceship in orbit, plunging it onto Europa with all of it's leftover nuclear cargo set to detonate on impact.

I can see nothing wrong with this plan. There can NEVER be anything wrong with a nuclear explosion on a virgin planet that may or may not piss off space Cthulhu.

I'm not the only one! Ask Xantalos how's the family, eh? Worth reminding him.

[Sheb]

10ebbor, as I said the sensors are only a few tens of meters apart. Now, the problem is that a given ice length will absorb a given proportion of the light.

Let's say 20m of ice let 90% of the light through (which I find ridiculously optimistic). Then, 20km of ice will let 0.9^1000 of the light through. That works out to something on the order of 10^-46. I'll let you work out what a ridiculously powerful laser we'd need to communicate through.

[10ebbor10]

It all depends on the wavelengths you're using.  Not everything type absorbs as much energy, after all.

[Sheb]

True enough, but I doubt any wavelength could go through 20km of water. There is a reason submarines surface to communicate after all.

Edit:

Let's do some math. The amount of light that goes through a given amount of matter is given by Lambert-Beer's law I= I0*e^(-ax),
where x is the distance in cm, I0 the initial light intensity and a the attenuation coefficient.

Looking at these graphs (okay, it's for liquid water, but ice isn't significantly different), the minimal absorption is in the blue wavelength, around 420 nm. There, it's around 0.003.

For 20 km of ice, we'd get an attenuation of e^(-0.003*2,000,000) = 6,6*10^(-2589)

A good light detector can detect a single photon, but to detect one, you'd need to send an average of 10^(2589) photons. A single photon's energy is given by E=hv, with v the frequency, and h the planck constant (~10^-34). At 420 nm, a single photon contain 7*10^-29 J of energy. Thus, you'd need to output around 10^(2560) J of energy with your laser. To compare, the sun output 10^34 J per year.

So yeah, if you get access to this kind of energy, light is a viable option. Not because you'll get a laser through the ice, but because you'll vaporize the whole of the solar system, which we should be able to detect quite easily.

[10ebbor10]

You could employ relay stations that you leave behind on your way down. I dunno.

[Sheb]

It could work and be easier to use that a cable, but then a single malfunction would cut your comms, and since you'll probably need a station every few meters, or tens of meters at best, I doubt it'd be easier that a big spool of cable.

[10ebbor10]

You need a station every 10 meters to spot the light emission of collision of subatomic particle. I'm pretty sure we can do much, much better if we actually used a stronger, optimised signal.

Also, the signal malfunction also applies to the wire, which would suffer significantly from the iceshelfs movement. (Europa deforms significantly due to tidal effects. That's the cause of the liquid water). With a drone system, you could space them so that when a given drone fails, the 2 next to it can still continue communication, albeit with tremendously reduced signal quality.

[Osmosis Jones]

It all depends on the wavelengths you're using.  Not everything type absorbs as much energy, after all.

I got ninja'd by Sheb, (I got distracted for a while when browsing... >_>) but here's a pretty indepth compilation of the absorbance data for ice from UV to microwave, scroll down to the conclusion to see the graphs together. Lowest is indeed in the blue region, at approximately 390nm.

At that point, light has a mean absorption distance of >700m in pure Antarctic ice.

At nearly a kilometre per light relay, it almost seems plausible to go through 50km of ice...


(Of course, you'd have to align the bastards too...)

EDIT: My bad. Misread that second link... *there is evidence to suggest the absorption distance MAY BE higher than 700m*

[Sheb]

Does it? We know it shift a lot on geological timescale, but we don't know much about shorter timescale.

Anyway, as I said, we cannot do much better, because it's an exponential relation. And we can't gain much from optimizing the frequency, because Cherenkov radiation (detected in the IceCube experiment) is alredy in the minimum absorption zone of the spectrum.

Moreover, spacing them would be difficult, as you'll have a single shaft. If you want redundancy, it means you need to halve the distance between substations. Still, it is true that it might be more practical than a big cable if the ice move a lot.

Also, each substation would need its own power supply and everything. If effect, you'd be sending hundreds of probes instead of one.

EDIT:

Okay, apparently I was wrong, and light goes through ice much more easily that I though. Using the data from Jones' first link, and correcting for temperature (absoprtion apparently rise with temperature, and Europe is cold), we get an attenuation coefficient of ~2*10^-6. Over 20km,  around 1% of the light goes through. Not going to be easy, but not impossible.

Although of course this assume pure ice, cracks, dust or any number of things could cause a lot of problems.

[MonkeyHead]

... or alternativley a tiny fibre optic bundle, giving much more bandwidth for a lot less mass.

[10ebbor10]

... or alternativley a tiny fibre optic bundle, giving much more bandwidth for a lot less mass.

And a very significant change of failure. The ice moves, and well, the melting and refreezing creates quite a bit of stress as well.