«It [i e, «habitable»] means a rocky planet that is in the right orbital region around its star where the temperature is moderate enough for liquid water to exist on its surface without freezing or boiling away. To give an idea of how generous this is, Earth is habitable under these criteria, but so are Venus and Mars, which are scarcely garden spots.» The average surface temperature on Mars is 227 K, max 268 K, the average surface temperature on Venus 735 K. On neither of these planets is water liquid on the surface....

Henri

"Chart a course, Commander Sulu... warp 5"

"if a world was 5° C (8° F) warmer than the Earth and had more water, it would enjoy the biodiversity of a rainforest over much of the planet."

Interesting comment given the worry about the earth's global warming and melting ice caps (read more water)!

Whoa. Lots of speculation going on here. There are thousands of reasons the earth is habitable for us not just four. Being closer to a cooler star would lead to more radiation. Being larger would mean greater gravity so space travel would be more difficult. Having different oxygen levels would mean that fire would be impossible or out of control. 20% OXYGEN IS IDEAL with just 5% more or less limiting any industrial processes needed for progress. Not having fossil fuels would make metal refinement unlikely. Not having a moon and tides would mean nutrient transfer would be difficult and limited. Being all rain forest would reduce the abundance of life. Cold oceans and climate lead to greater schools of fish and wildlife. Ocean currents lead to greater regions that are thermally stable. Rotational velocity contributes to prevailing winds and storm intensity along with temperature extremes between night and day. Even mountain ranges add to climate and life diversity. The list goes on and on why we were made for our earth and for us it is the Garden of Eden. This research shows a lack of thought about what is habitable. If we can't thrive there, it is not habitable and sustainable for us.

"if a world was 5° C (8° F) warmer than the Earth..." more biodiversity. But, NO, when it got just 2° warmer, its people would panic, try to make a sudden switch in energy use, and go extinct. ... AND, that's how you get biodiversity.

@piperTom - LOL, that was a good one.

There are planets that are “better than Earth” and “more suitable for sustaining life for a longer period of time than our planet”?

Well, yeah, and it’s because there are no humans on them. How ‘bout we leave these planets—and, more important, any life forms that may have developed there—the heck alone?

It’s our own grimy, greedy, clutching, covetous, self-serving, war-mongering hands that have all but ruined the one we already live on.

Your article says: "It means a rocky planet that is in the right orbital region around its star where the temperature is moderate enough for liquid water to exist on its surface without freezing or boiling away. To give an idea of how generous this is, Earth is habitable under these criteria, but so are Venus and Mars, which are scarcely garden spots."

However this is wildly inaccurate. The average temperature on Venus is 864 degrees Fahrenheit (462 degrees Celsius). Water boils at 212 degrees Fahrenheit (100 degrees Celsius). Venus, by the reported definition is not habitable.

Yes, I agree with Brian M and piperTom and have thought about the 5 degree increase in the earth's temperature too. So much for all the hulabaloo about global warming and such, according to this article it can't be a bad situation for earth either than.

So what if they are suitable for life? Being light years from here,we will never visit them. Best we can hope for is finding they have an advanced civilization we could trade notes with,but that would take 100 years one way.