So a British (supposedly metric) site says it's 36 feet. Meanwhile, an American (supposedly "Imperial", or whatever it's called these days) site says it's 10 meters. Such a strange world, this Internet thingy.

So, what are the chances of a huge Total Recall like ice melt and 'blue skies on Mars'?

The core of Jupiter is metallic hydrogen - which only exists at slightly above absolute zero when it's at normal pressures. The core of Jupiter is, however, under very high pressure - which forces the hydrogen to take on its highest-density state, even though the temperature there is extremely high.

Since the mystery sea is buried very deeply under the ice, it is probably under very high pressure. Is it possible that, under high enough pressure, ice will revert to a higher-density state (liquid water) in the same way that hydrogen does?

If that's true, then the underground sea could well be liquid water, despite the temperature. However, I suspect that the mystery sea would have to be buried extremely deeply for the pressure to be "high enough".

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Alternatively, ice is a very good insulator of heat (think of igloos). If there's some geothermal activity at the bottom of this sea, then the ice above it might insulate it from the coldness of the Martian atmosphere, allowing it to remain liquid.

Is that supposed to be a troll?

I can't really see the point of the post otherwise.

I found the use of imperial on a site which should be metric somewhat amusing and disturbing myself. But here's the rub - a 'foot', metricised as a 30cm ruler, is a metric measure of convenience these days. Using miles on the other hand is just plain stupid.

Now in relation to the Blue Sky on Mars scenario, ala Total Recall, someone mentioned, there's a few things going against the Red Planet for that to happen.

Firstly, the planet doesn't have a sufficient magnetic field for a dense atmosphere and hence liquid water to form. Being a smaller body with less mass and less gravity doesn't help matters either. At some time this wasn't the case and Mars had a more dynamic climate and atmosphere. But being a smaller planetary body, it cooled more quickly than the Earth resulting in the mechanisms which create the Mars' magetic field, believed to be the turning and churning of the inner cores, slowing down or stopping all together, resulting in the field disipating and much of the atmosphere and possibly a great deal of water being lost into space, carried away by the charged particles of the solar wind. What didn't rise, sunk into the crust.

Even if you could melt these frozen oceans (and it's believed a similarly large deposit of water sits under the north pole), it would gradually or rapidly (no one is quite sure) drift off into space. Without somehow re-establishing the magnetic field, a denser and warmer atmosphere cannot form. In a thin atmosphere, liquid water quickly evaporates.

But don't take my word for it, http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31025 .

"I found the use of imperial on a site which should be metric somewhat amusing and disturbing myself."

Who decided that this site should only use metric? You? The UK government? The US government?

I have no knowledge of any rule or law which states that only metric measurements should be used here.

"Disturbing"? If such a small thing as the use of feet disturbs you, perhaps you are indeed "disturbed". You seem to be some kind of metric fascist.

El Reg should report all distances in the itrw! (Good enough for Senurset I, good enough for us.)