[henkster]

Gravity would be a serious problem.

[GraceG]

Not really, even a really large planet like that would only have gravity that is 1.5X to 2X the gravity on earth due to how gravity works via the square of distance.

2X gravity is not all that bad, it would be like being overweight when fit and for someone who is fit you would get used to it.

[Telepathic Intruder]

Gravity would be a serious problem.

We would all need one of those motorized whatever-you-call-ems that almost ran me over a couple times at Walmart. Anyway, I'll bet most star systems have at least one planet in the habitable zone. The real problem is the right combination of conditions. Water, an atmosphere, a magnetic field, maybe even a large moon. Tidal forces were probably responsible for causing recombinations of amino acids resulting in the first self-replicating protein. There are probably a thousand other factors that make conditions for life such as ourselves extremely rare. Just finding a planet in a star's habitable zone means nothing in itself.