June 20, 2008

Super-Earth vs. ExoGaia

Gliese 876 dSuper-Earth. It conjures a visceral imagery of an earthy ocean-blue in our minds. Just because it contains the word "Earth" brings people to think that it is similar to our world - full of life, and well...Earth-like.
The truth is that it is a misnomer.
The basis of any terrestrial exoplanet being called a Super-Earth is based on mass. Whenever a rocky exoplanet is a bit more massive than the Earth, specifically up to 10 times the mass of the earth, then it falls into the criterion of a "Super-Earth".
Yet, nobody really knows if any given Super-Earth is similar to our Earth. It may have a different climate, or different surface features (icy/dry), different atmosphere. The list of differences may go on, and by far outweighs the similarities. Yet we still choose to name it Super-Earth. The exact history behind the word evades me, but it tells me something about humanity's yearning to find a twin of our home, possibly fueled by our desire to find out if life is unique to our planet - if we are alone in the universe.
This brings me to the question: what if exoplanetologists finds an exoplanet that has exactly the same mass as the earth...and has Life? Earth's Twin - it has got to be called 'ExoGaia'. Welcome to the beginning of the ExoGaia Hypothesis.
And so, the search for ExoGaia continues...