The latest issue of Science has a fascinating article on Exotic Earths—it contains the results of simulations of planet formation in systems like those that have been observed with giant planets close to their stars. The nifty observation is that such simulations spawn lots of planets that are in a habitable zone and that are very water-rich.
(click for larger image)
Final configuration of our four simulations, with the solar system shown for scale. Each simulation is plotted on a horizontal line, and the size of each body represents its relative physical size (except for the giant planets, shown in black). The eccentricity of each body is shown beneath it, represented by its radial excursion over an orbit. The color of each body corresponds to its water content, and the inner dark region to the relative size of its iron core. Orbital values are 1-million-year averages; solar system values are 3-million-year averages. Note that some giant planets underwent additional inward migration after the end of the forced migration, caused by an articial drag force. This caused many hot Earths to be numerically ejected, but had little effect outside the inner giant planet.
Dynamics of Cats has a better summary than I could give, and it leads in with this lovely illustration of an hypothetical alien organism on one of these hot water worlds.
The only thing cooler than a cephalopod has to be a tentacled alien cephalopodoid. There’s a high-res version of that image at Dynamics of Cats—and I’ve got a new desktop picture.
That’s like, really old, PZ. I blogged about the evolution of alien cephalopod intelligence way back in June. (-;
Ultra water rich planet ar 0.1 AU ? Is this simulation really accurate ? Anyway… I suppose it would not remain water rich for very long…
It just too bad that a “hot water world” would only allow for small cephalopods to exist. A “cold water world” on the other hand has pontential to generate larger cephalpods, a trend I like to call Encephalization.
I know that planetologists think of Earth primarily in terms of all that rock beneath our feet, with a thin film of biology that helps form more exotic geology occasionally, so there isn’t a lot of difference in their minds between Earth and Venus — but this ‘Hot Earth’ terminology is pretty deceptive, I think. If they only mean a metallic-rocky body with water on its surface, then they need to come up with a better descriptor. ‘Hot water worlds’ maybe?
Besides, as I recall, some theories hold that Venus used to be a ‘Hot Earth’-type planet in the past, before the Sun warmed up and greenhouse loop kicked in, evaporating all the water. Is it still a ‘Hot Earth’ even though it doesn’t have any water left?
If the oceans get too deep, the planet ends up with a layer of ice between the ocean (where any organisms would presumably be swimming/drifting/whatever around) and the core (where all the minerals and stuff are). That would make getting minerals to the ocean quite difficult I’d think. I’d guess such water-rich planets are going to be sterile.