If earth had been slightly smaller and less massive, life might never have gained a foothold. They key to life on Earth as we know it, scientists figure, is plate tectonics — the forces that move continents and build mountains. And the more massive a world is, the thinner its plates are. Thinner plates are weaker and more easily moved and so able to support the kinds of crucial planet-shaping plate tectonics experienced on this planet over the billions of years that life evolved from simple one-celled organisms to complex creatures that can fly, swim and read. "Plate tectonics are essential to life as we know it," said Diana Valencia of Harvard University, who presented research on the topic here Wednesday at a meeting of the American Astronomical Society. "Our calculations show that bigger is better when it comes to the habitability of rocky planets." The study reveals Earth has been on the edge of habitability from the beginning, and just eked by to allow life-friendly conditions. The results give hope to astronomers looking for life on other planets. "It expands the potential to find life on other planets that are different from Earth," said astrophysicist Sara Seager of MIT, who was not involved in the study. She added that Valencia "has shown us that we can have hope that we can have life there." Not too hot, not too cold: Plate tectonics, Valencia explains, is what allows the carbon cycle on Earth to operate. So as plates spread apart from each other, slide under one another, and even crash into each other to lift gigantic mountain ranges like the Himalayas, they also recycle carbon dioxide.

This greenhouse gas acts as a thermostat to keep Earth balmy — but not scorching — over geologic time scales. "Recycling is important even on a planetary scale," Valencia explained. Valencia and her Harvard colleagues, Richard O'Connell and Dimitar Sasselov, examined so-called super-Earths more than twice the size of Earth and up to 10 times as massive.

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The whole statement is kinda funny. Earth, the only "truely known" planet to harbor life is criticized as compared to??...

Wow, I wonder how they got to "examine" these super planets? After all we barely know enough about our sibling planets, let alone any other planets out of telescope range. When I think "examine", I think of my Doctor giving me a physical... however this seems to be far from the case in observing these super planets. To me it looks like a bunch of mud* slinging, and seeing what sticks to the wall. (* replacement word for brown smelly excrement).
What happened to science? Are they all speculating and hypothesizing their way into the science digests?

No I'm not really asking the questions above, I'm just wondering why so much "speculation" seems to be the stuff of science these days.

Well-- Mars, Jupiter's moon Europa, Saturn's moons Titan and Enceladus (which may have liquid water) for starters

It would be funny if we have a small homeworld. All the ETs would be laughing at our puny little world that can only hold 10 billion people. "Why back on Whycxl we have 100 billion on that world alone."

Its true tho. Only a complete idiot of a "creator" would consider anywhere in this universe let alone this planet as a place life would thrive.
Everywheres to hot, to cold, or rains rocks and acid, and that includes Earth!

Lucky for us life itself doesnt agree...

It is exciting what they have found on all of these moons above these cloud covered planets. Could be the moons are evolving into home worlds for the Jupitarians or Saturnians.

It's difficult for me to visualize what the sky would look like if you were living on a moon. You'd have this gigantic object rising and setting every day. And then you'd have the sun dancing around in a really complex pattern.

Your theory is wrong, life finds a way.