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Name: Josh A.
Status: student
Age: 20s
Location: N/A
Country: N/A
Date: 7/15/2004


Question:
Is it possible to have a 100% liquid planet?


Replies:
Yes it is possible in principle, but the details depend on both the material and on the mass of the planet. If the liquid was iron or nickel and if it is hot enough then it is possible for a planet to be completely liquid from the surface to the core. However, the planet would loose heat into space and progressively solidify.

The heat inside the Earth is maintained by the decay of radioactive elements that are spread throughout the interior. Therefore, the heating can be maintained for a period that depends on the amount of radioactive material present. If the planet is too massive, then the iron/nickel will be in a solid phase in the core because of the high pressures there.

What about a "water" planet?

When far from its star, the liquid will freeze (as with comets) and when too close it will boil off into space. In the narrow range of temperature where the liquid phase could exist, the liquid would immediately boil because it is surrounded by the vacuum of space (there is no liquid phase possible in a vacuum). The atoms/molecules would then form a gaseous atmosphere provided there was enough mass to keep the atmosphere from drifting off into space. But if it formed an atmosphere it would no longer be a "liquid" planet.

Regards

Grant Christie (by way of Howard Barnes)
Stardome Observatory
Auckland
New Zealand



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