a theory

[Madame Adequate]

what makes our planet sustainable compared to mars and venus was the carbon cycle through rocks and rivers. messing it up would be as catastrophic as removing the moon.

And about a thousand other factors, such as makeup of the atmosphere, quantity and forms of water and other liquids, distance from the sun, age of the planet, what has impacted the planets and at what speeds, angles, carrying what, at what size, etc. etc. etc..