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Europa's Ice May Be Miles Thick
serutan writes "Space.com has an article detailing recent measurements of the shell of ice covering what is believed to be an enormously deep ocean on Europa, which could harbor life. The thickness of the ice -- many times the previous estimate -- poses a major obstacle to sending a lander that would burrow down through it to the water. [Seems like if they could make the probe kinda warm it would eventually sink through any amount of ice.]"
If they run the probe with Intel chips it should generate enough heat...
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The whole idea is to look for life... You gonna do this by dropping a comet on them??? How they going to take this?
Seriously, you could disrupt things that way even if it's only bacteria mats.
Seems like if they could make the probe kinda warm it would eventually sink through any amount of ice.
That's a bit of an understatement. Let's do a quick calculation, shall we?
The article says that the ice is at least 19km (11 miles) thick. Let's assume we can somehow magically make our probe fit into the volume of a square foot or 30cm per side. That means we have about 1700 square meters of ice to melt, which is around 2e6 kilograms.
Europa has no real atmosphere, the pressure at the surface is around 1e-11 bar (1e-6 Pa) -- i.e. almost nothing. So the ice would most certainly vaporize rather than melt, and at a temperature lower than 0C. See this neat phase diagram of water. As we go down farther the pressure will necessarily increase, but I don't feel like calculating it exactly. Based on the phase diagram I'll use 200K as the approximate transistion temperature. It's close enough to be within an order of magnitude of correct.
The surface temperature of Europa is approx -260 dF (111 Kelvin), so to raise it to 200K results in a temperature difference of 89K. The specific heat of ice is around 2e3 J/(kg*K). That means our task will require about 3.5e11 Joules of energy. Let's say we let this process take 100 years at a steady rate. This comes to about 111 Watts. Suddenly "kinda warm" really doesn't cut it.
When you have a self contained source of power that can supply 111 W constantly for 100 years and fit into a square foot of volume, please let me know. Surely, you would have solved our energy crisis by now.
PS - Solar panels are pretty much useless after you get farther from the sun than Mars. That's why probes like Cassini needs radio-isotope thermo-electric generators.
Good idea, but not necessarily. Ice packs tend to be dynamic flows with upwelling, downwelling and lateral movement. Metling say a few meters a day, would still take year or even more to reach the ocean below. In addition, the pressures below the ice pack will be immense once the liquid ocean is reached. Not to mention the giant pod eating monsters that probably lurk there.
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Unfortunately, I believe they didn't have too much luck. Their cylindrical probe would only melt the ice right under it. The walls would freeze back into place and hold it with friction (since ice expands, and as such would create pressure on the hull). I wonder if they would have been more successful with a raindrop-shaped design, where the pressure from the refreezing ice would actually help propel it downward. In any case, the high pressures involved would probably crush any payload.
The other problem was how to relay any information it harvested back to the surface, so it could be retransmitted to Earth. H2O blocks most radio waves pretty well, and stringing a wire all that distance suffers similar problems as the probe itself -- you'd have to keep it hot to keep moving.
Until then, we'll just have to rely on remote sensing...
The cracks once formed last for many many years. I don't offhand remember how many millenia they last for. But they are easily visible and well mapped. The crack forms, the water freezes over, but (the article argues) water should be forced into the crack due to tidal forces. Eventually, the crack will seal up but as I said it would take a long time.
Anyway, sounds like it's worth a shot.
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