[meteorite-list] Starless planets may be habitable after all

[Jeff Kuyken]

http://www.newscientist.com/article/mg20928005.200-starless-planets-may-be-habitable-after-all.html

Starless planets may be habitable after all.
20 February 2011

LIQUID water may survive on free-floating planets that have no star to warm 
them. If they also support life, they could act as stepping stones to spread 
life around the galaxy.

Gravitational tussles with other planets or passing stars can eject planets 
from their solar systems. But even in the cold of space, these wayward 
worlds could stay warm, thanks to the decay of radioactive elements in their 
rocky cores.

Dorian Abbot and Eric Switzer of the University of Chicago calculate that 
rocky planets with a similar mass to Earth could remain warm enough to keep 
water liquid under thick, insulating ice sheets for over a billion years. A 
planet with the same fraction of water as Earth could keep a subsurface 
ocean liquid if it was 3.5 times Earth's mass. But a planet with 10 times 
Earth's water concentration could do this if it weighed just one-third as 
much as Earth, they say (arxiv.org/abs/1102.1108).

"It's a really interesting idea," says Lisa Kaltenegger of the 
Harvard-Smithsonian Center for Astrophysics. "But we would have to land on 
[a planet] and burrow down to see if life is possible."