The Scramjet idea is decades old, and most of the plans I ever saw for it call for a separate reuseable scram booster that detatches in the uppper atmosphere; if you make it an itegral part of the vehicle, it's just dead weight from there up.

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I was wondering - assume that there *is* a 100 kilometer depth oceanic layer under the ice crust of Europa. What is the pressure going to be at the bottom?

interesting question. I suppose it could be any part of a very large range - from 0 to really big.

I imagine it is closer to the low end.


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calculation, but it's only really used for liquids
PRESSURE = DENSITY x DEPTH x ACCELERATION OF GRAVITY

density is less than 1 for ice
depth = 100km
gEuropa = 1.31 m/sec^2

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With an all-encircling ice shell you have to take its weight into account. Ice is 0.9 density of water, so 100 km of water plus 10 km of ice is equivalent to 109 km of water.

Ignoring the ice, the answer I get (to three significant digits) is 1330 atm. A bit more than the deepest ocean trench on Earth.

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Most people I know believe Europa is a continent...
(and full of complex life )

did you use the gravitational acceleration of Earth or of Europa?

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Have you heard about the renewed speculations that Titan might have underground oceans, too?
I suppose they would have to be substantially different than on Europa...

Europa, of course. On Earth the pressure at the bottom of a 100 km ocean would be 10,000 atm.

Why do you suppose that?

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I agree with this.

I've always thought that life could not originate on a world with low temperatures, unlike early earth which had very hot temperatures. Chemical reactions needed to be fast under high temps. to get life going.

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reactions at colder temperatures just take longer.

Oh, and if there is an ocean under the surface of Europa it won't be that cold.

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If th tidal stresses on Europa are slightly less than Io's, then there'd be a moon with a high temperature near the bottom of the ocean, where life can develope.

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It was more a question than a claim. How would this ocean be different?

As Titan is very different than Europa:
both its crust and its hypothetical underground ocean have a different composition than on Europa,
and Titan's ocean would also probably be located deeper than on Europa.
Titan's surface is very different too, with that dense atmosphere, active weather patterns, etc.
Well, and last not least, they have different orbits around different gas giants...

All of this should affect conditions in the hypothetical underground ocean, shouldn't it?
Any ideas on how?

It's been speculated that the water layer would be mixed with ammonia, which would act as an antifreeze, so the ocean could be a lot colder, I seem to remember a figure of -30 degrees C being quoted. If an active cryovolcano is indentified on titan a future lander might be able to sample material from it directly.

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True! And we do not have to think only of highly evolved beings solving problems or thinking of the nature of their numen. Few cells will mean life is out there although I would like to see that life out there is beyond our imagination.

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that is a highly evolved image you have there.

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