SPACE.com -- Habitable Planets: Four Types Proposed

[dracodraconis]

SPACE.com -- Habitable Planets: Four Types Proposed

A UK academic has suggested four classifications for habitable worlds. Class 1 is Earth-like and acts as a baseline. Class II are Mars-like planets that were formerly habitable like Mars and Venus. Class III are Europa-like ice worlds with liquid oceans. Class IV are worlds composed almost entirely of liquid water.

Comments

[lyanna-beth.livejournal.com]

Well, in Class IV worlds, you wouldn't have to worry about lack of water, just perhaps a lot of filtration and hydroponics, but it's possibly easier than an European ice-world? Mind you, depends on the temperature of the water. :)
And you did say "almost" entirely...

[dracodraconis.livejournal.com]

There could be a sold core to the world, or just an ice core. Scientists are still out on whether rock is required to form life. One theory is that a chemical "soup" was all that was required on Earth, while others suggest that chemicals in rocks were required to interact with chemicals in the water and to form protected and stable pools in which life could form.

[ancalagon-tb.livejournal.com]

Living on an all water world would be ... challenging. Imagine the storms!

[ancalagon-tb.livejournal.com]

Oh, and water worlds were proposed in Master of Orion II :P