That's implied by the charts linked - the moons are not large enough to hold onto an atmosphere, Mars-sized seems to be around the limit. The point I'm respond

That's implied by the charts linked - the moons are not large enough to hold onto an atmosphere, Mars-sized seems to be around the limit. The point I'm responding to is "It's too cold out there". Maybe an earth-size planet with an atmosphere like Venus would still be warm?