Are Super Earths More Habitable?

Astronomers have discovered hundreds of Jupiter-like planets in our galaxy. However, a handful of the planets found orbiting distant stars are more Earth-sized. This gives hope to astrobiologists, who think we are more likely to find life on rocky planets with liquid water.

The rocky planets found so far are actually more massive than our own. Dimitar Sasselov, professor of astronomy at Harvard University, coined the term "Super-Earths" to reflect their mass rather than any superior qualities.

But Sasselov says that these planets – which range from about 2 to 10 Earth masses – could be superior to the Earth when it comes to sustaining life.

It is said that 99 percent of all species that ever lived have gone extinct. Earth, it seems, is a tough place to call home. Our planet has gone through Ice Ages and global warming trends, it has been hit by comets and asteroids (leading, in one case, to a mass extinction that felled the mighty dinosaurs), and the amount of oxygen in the atmosphere has risen and fallen over time. Our planet is always in a state of flux, and life must adapt to these changes or die.

The shifting of tectonic plates is another example of Earth's restless nature. Continents bang together, forming mountains, only to be later torn apart. Islands grow from underwater volcanoes, and elements are liberated from rocks when they are melted beneath the crust.

While all this geologic activity makes us literally stand on shaky ground, scientists have come to believe that tectonics is one of the key features of our planet which makes life possible. If not for tectonics, carbon needed by life would stay locked within rocks.

The fear today is that too much carbon dioxide in the atmosphere will lead to global warming. Yet too little carbon dioxide in the atmosphere would make Earth a much colder place, and the photosynthetic plants and algae that rely on CO2 would perish. The demise of these oxygen-producing organisms would leave us all gasping for breath.

According to Sasselov, Earth's mass helps keeps tectonics in action. The more massive a planet, the hotter its interior. Tectonic plates slide on a layer of molten rock beneath the crust called the mantle. Convective currents within the mantle push the plates around. For smaller planets like Mars, the interior is not hot enough to drive tectonics.

Super Earths, with a larger and hotter interior, would have a thinner planetary crust placed under more stress. This probably would result in faster tectonics, as well as more earthquakes, volcanism, and other geologic upheavals. In fact, Sasselov says the plate tectonics on Super Earths may be so rapid that mountains and ocean trenches wouldn't have much time to develop before the surface was again recycled.

It might also lead to other consequences. I bet that if the world is more plastic, its going to effect those living on it - cultures or organisms - more than what people realize. The rate of continental formation, degradation, and weathering would greatly influence life in general. Could you imagine a world that was constantly upthrusting new mountain ranges and isolating life on a grand scale, producing new populations very frequently? Talk about a speciation heaven! Then again, imagine what the world would be like if the continents moved at a rate of 1 m/year or more. o.O