How can I get a very large air bubble floating under Europa's ice?

I hope this isn't a stupid question ("just add air").

I would like my intrepid explorers to have drilled through the ice of Europa and into the water without creating a geyser (they plugged the hole behind them). This is assuming a liquid subsurface ocean.

Once under the ice, they encountered a very large, stable cavern of air between the water and ice. Their submersible 'surfaces, and when they look around they see water, and when they look up they see ice. It measures several kilometers wide and at least one km high to the ice. I am not married to those dimensions, though.

It doesn't necessarily need to be breatheable, but it should be enough that they can exit their vehicle with scuba-like gear (ie - breathing and warming/cooling apparatus). However, bonus if they surface and the pressure, temperature, and composition are suitable, however shortly.

I really hope this isn't as straightforward as it seems.

posted over 9 years ago

Mikey‭

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