I mean the smallest, lowest mass, and/or lowest g terrestrial planet that can hold onto and support a favorable atmosphere for potential life, and is in the zone where water can exist as a liquid. I'm really asking: what's the smallest "Earth" possible? I heard that the upper limit for "Super-Earths" is 14 times the mass of the earth, and there is an extrasolar planet that is close to this mass. Someone calculated that it would have an upper limit of 3.5g at the surface, which would make life very squat if it even got past a bacterial stage. It made me wonder what the opposite conditions would be, and what the lower limit has been calculated at. I can't find any good information on the lower limit though (bad search queries?), so I'm asking here. Some requirements to considered to be an "Earth" raise these questions: What's the smallest a body can be and still hold onto a decent atmosphere (within the habitable zone, Titan has an advantage of extreme frigidity), and how long can it hold onto it for? How long can such a small planet stay warm and maintain a magnetic field? What are the lowest g conditions that life can start in, and would biological molecules have trouble forming in low percentages of earth's gravity? Could something, say, 10 times the mass of earth's moon (making it an 8th of earth) sustain favorable conditions for any significant length of time?