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The usual metric for whether a planet is habitable or not is to ascertain whether liquid water could exist on its surface. Most worlds will either be too cold, too hot or of a type (like Jupiter) that may have no solid surface and be swaddled in noxious gases.

In days gone by, scientists would speak solemnly about our solar system's 'habitable zone' - a theoretical region extending from Venus to Mars, but perhaps not encompassing either, where a planet would be the right temperature to have liquid water on its surface.

Mars is the only place in the solar system where it's possible for life to become multi-planetarian.

Ocean planets might be very common in the universe because water is very common in the low-temperature environments where planets form and evolve. This might be especially true for super-Earths, which can retain volatiles more easily thanks to their larger mass and surface gravity.

We have altered the physical, chemical and biological properties of the planet on a geological scale. We have left no part of the globe untouched.

Plate tectonics is not all havoc and destruction. The slow movement of continents and ocean floors recycles carbon dioxide dissolved in the oceans back into the atmosphere. Without this slow speed carbon cycle, Earth's temperatures would cool dozens of degrees below your comfort zone.

Data from orbiting telescopes like NASA's Kepler Mission hint that the tally of habitable planets in our galaxy is many billion. If E.T.'s not out there, then Earth is more than merely special - it's some sort of miracle.

Now, Venus is an extremely hostile environment, and as such presents a lot of challenges for a science fiction author who wants to create life there. However, as I began to research it more thoroughly, I found myself intrigued by the possibilities the world offers.

Mountains aren't eternal: even the most imposing massifs are smoothed away by weathering in a few hundred million years or less. Plate tectonics makes new ones, and without it, our future would be flat.